Broadband Connectivity in 5G and Beyond: Next Generation Networks 3031068653, 9783031068652

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Simranjit Singh Gurpreet Kaur Mohammad Tariqul Islam R.S. Kaler   Editors

Broadband Connectivity in 5G and Beyond Next Generation Networks

Broadband Connectivity in 5G and Beyond

Simranjit Singh • Gurpreet Kaur • Mohammad Tariqul Islam • R.S. Kaler Editors

Broadband Connectivity in 5G and Beyond Next Generation Networks

Editors Simranjit Singh Department of Electronics and Communication Engineering Punjabi University Patiala, India Mohammad Tariqul Islam Electrical Electronic and Systems Engineering Department of Electrical Electronic and Systems Engineering Universiti Kebangsaan Malaysia Bangi, Malaysia

Gurpreet Kaur Department of Electronics and Communication Engineering Chandigarh University Mohali, India R.S. Kaler Department of Electronics and Communication Engineering Thapar Institute of Engineering and Technology Patiala, India

ISBN 978-3-031-06865-2 ISBN 978-3-031-06866-9 https://doi.org/10.1007/978-3-031-06866-9

(eBook)

© The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

Preface

In broadband network connectivity, the chunk that connects the central office to remote head to serve the large number of cellular subscribers is termed as fronthaul network, which contains multiple optical line terminals (baseband units) and optical network units, respectively. Research on fronthaul network is spurred by 5G and future vision of beyond network in terms of data rate and spectrum efficiency in multiple gigabits or terabits, extended fronthaul coverage distance, and ultra-low latency to deal with the growing explosion in mobile population, smart gadgets, and machines. The large volume of subscribers in 2022 has already hit assumed peak levels, ushering a new generation. Therefore, critical fronthaul network demands the strongest broadband network connectivity that can be feasible by the rolling out of 5G and beyond. For broadband, 5G and beyond network would provide us a afresh network infrastructure that can beat the previous generation with the huge vision that presents 1000 speed, flexibility, capacity, and efficient network. Broadband always considers the locations, whether urban or rural, to implement the various transmission technologies as per requirements like fiber, wireless, and satellite. To match the vision of 5G and beyond, researchers are focusing to enhance the network performance efficiently to meet the mobile subscriber’s demands. For these scenarios, there are some aspects that are needed to be investigated in depth, such as enhanced fiber optic–based communication network system, along with the robust massive MIMO antenna. To enhance the efficiency of wired fronthaul network, fiber is the most attractive and potential medium for transmission that can provide ultrahigh bit speeds, efficient utilization of large volume of bandwidth, unused millimeter wave spectrum band, and low jitter. Optical technologies are very reliable in transmitting electronic signals in form of light, which is more durable. Various transmission techniques have been experimentally tested by installing the fiberbased network in limited areas. Therefore, telecommunication organizations are highly recommended to extend the deployment of fiber broadband after getting the positive results. Under the ITU-T and IEEE standards, passive optical network technologies like E-PON, G-PON, 10G-PON, and NGPON2 have been recognized under the different series with different features and their specifications. Corresponding these technologies, many existing multiplexing techniques that are v

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TDM-PON, WDM-PON, OFDM-PON and TWDM-PON available to boost up the system infrastructure under the different standardizations. The advance modulation techniques are compatible to meet the future fronthaul network demands in terms of multiple Tb/s of bit rate and ultra-low latency. with the help of above-mentioned multiplexing techniques under the specified parametric scales of telecommunication mobile unions. Fronthaul frames some special key points to augment the objectives such as long distance to be covered, latency discount, traffic balancing, to modulate the high frequency and utilization of network resources in efficient manner. The convergence of the MMWoF and NGPON will provide great potentials to the future fronthaul network. To achieve the expected outcomes, researchers are focusing on exploring the area of antenna to enhance wireless network performance by densifying the small cells in urban areas. As per the network requirements, massive-MIMO is the center of attraction that will be compatible to enhance the mobile subscriber’s experience and overall efficiency of network. The telecommunication market is also showing its interest for the innovative and smart fronthaul network development to utilize the heterogeneous networks. The MIMO antennas are capable of modulating the high spectrum band millimeter waves that enhance the utilization of large bandwidth to accommodate the giant subscribers. With the perspective of beyond network, the massive-MIMO will be the backbone of the broadband network for ubiquitous connectivity. The concept of beamforming is useful technology that will be beneficial to reduce the interference between the large number of mobile users. The present state of research of broadband connectivity for 5G and beyond fronthaul network needs to be more exploratory. There is still a necessity to take the steps forward to investigate the better next-generation network. This book aims to discuss the fronthaul network for 5G and beyond under the context of broadband network. We focus on the pivotal role of PON technologies using multiplexing techniques and different antenna designs to meet the requirements of MIMO. In addition, this book presents a comprehensive analysis of different transmission technologies that displays the innovative fronthaul architectures. This volume presents the massive experience and leads the research arena under the standardization. In this book, the editor has discussed openly about broadband connectivity for the 5G and beyond fronthaul network, and the book will serve as a useful reference for both postgraduate students as well as telecommunication researchers for learning more and taking further pioneering strides. Patiala, India Mohali, India Bangi, Malaysia Patiala, India

Simranjit Singh Gurpreet Kaur Mohammad Tariqul Islam R.S. Kaler

Contents

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2

Coexistence of Next-Generation Passive Optical Network Stage 2 and 5G Fronthaul Network . . . . . . . . . . . . . . . . . . . . . . . . . . Rajandeep Singh, Ritika Mahajan, and Ramandeep Kaur

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Design of Wideband MIMO Patch Antenna Array for Millimeter-Wave-Based 5G Wireless Communications . . . . . . . . Mandeep Singh and Simranjit Singh

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Fronthauling for 5G and Beyond . . . . . . . . . . . . . . . . . . . . . . . . . . . Harpreet Kaur, Simranjit Singh, and Ranjit Kaur

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M-Ary Signaling for FSO Under Different Atmospheric Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Harsimran Jit Kaur and Rubina Dutta

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Multiple Input-Multiple Output Antenna for Next-Generation Wireless Communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Manish Sharma

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Next-Generation Optical Wireless System for 5G and Beyond . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 Sahil Nazir Pottoo, Rakesh Goyal, Amit Gupta, and Monika Rani

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Performance Evaluation of 80-Gbps TWDM-Based NG-PON2 for Various Network Topologies . . . . . . . . . . . . . . . . . . . 127 Ramandeep Kaur, Simranjit Singh Tiwana, and Rajandeep Singh

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Performance Evaluation of Path Computation Algorithms in Generalized Multiprotocol Label-Switched Optical Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147 Monika, Simranjit Singh, and Amit Wason

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Radio over Fiber (RoF) for Future Generation Networks . . . . . . . . . 161 Baljeet Kaur and Neha Sharma

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185

Contributors

Rubina Dutta Chitkara University Institute of Engineering and Technology, Chitkara University, Patiala, Punjab, India Rakesh Goyal Department of ECE, IK Gujral Punjab Technical University, Kapurthala, Punjab, India Amit Gupta Department of ECE, IK Gujral Punjab Technical University, Kapurthala, Punjab, India Baljeet Kaur ECE Department, GNDEC College, Ludhiana, Punjab, India Harpreet Kaur Department of Computer Science, Punjabi University, Patiala, Punjab, India Harsimran Jit Kaur Chitkara University Institute of Engineering and Technology, Chitkara University, Patiala, Punjab, India Ramandeep Kaur Department of ECE, Punjabi University, Patiala, Punjab, India Ranjit Kaur Department of ECE, Punjabi University, Patiala, Punjab, India Ritika Mahajan Department of Electronics Technology, Guru Nanak Dev University, Amritsar, Punjab, India Monika Punjabi University, Patiala, Punjab, India Sahil Nazir Pottoo Department of ECE, IK Gujral Punjab Technical University, Kapurthala, Punjab, India Monika Rani Department of Mathematics, Kanya Maha Vidyalaya, Jalandhar, Punjab, India Manish Sharma Chitkara University Institute of Engineering and Technology, Chitkara University, Rajpura, Punjab, India

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Contributors

Neha Sharma ECE Department, Apeejay Institute of Management and Engineering Technical Campus, Jalandhar, Punjab, India Mandeep Singh Department of Electronics and Communication Engineering, Punjabi University Patiala, Patiala, Punjab, India Rajandeep Singh Department of Electronics Technology, Guru Nanak Dev University, Amritsar, Punjab, India Simranjit Singh Department of Electronics and Communication Engineering, Punjabi University Patiala, Patiala, Punjab, India Simranjit Singh Tiwana Department of ECE, Punjabi University, Patiala, Punjab, India Amit Wason Ambala College of Engineering and Applied Research, Devsthali, Ambala, Haryana, India

About the Editors

Simranjit Singh is an assistant professor in the Department of Electronics and Communication Engineering at Punjabi University, Patiala. He is the author and co-author of about 106 research journal articles, nearly 34 conference articles, few book chapters, and book on various topics related to optical fiber communication, information security, optical sensors, and antenna design. Thus far, his publications have been cited 714 times and his H-index is 15 (Source: Scopus). His Google scholar citation is 908, i10: 26, and H-index is 17. His Research Gate citation is 698, score: 24.78, and H-index is 14. The total impact factor of his SCI journal published is greater than 70. He is recipient of more than six research grants from the Empowerment and Equity Opportunities for Excellence in Science, SERB, Government of India; ASEAN-India STI Cooperation, Department of Science and Technology (International Multilateral and Regional Cooperation Division), Government of India; Visvesvaraya PhD Scheme for Electronics and IT, funded by MeitY, Government of India (two projects); Raman fellowship funded by the University Grants Commission (India); and Host Scientist of C V Raman International Fellowship for African Researchers 2016 of FICCI, Government of India. Dr. Singh currently serves as associate editor of IET Electronics Letters (SCI journal, Feb. 2021 to till date) and of IET Journal of Engineering (ESCI journal, Feb. 2021 to till date). Dr. Singh received best paper award for his paper published in Optics and Laser Technology Journal. He received Host Scientist of C V Raman xi

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International Fellowship for African Researchers 2016 of FICCI, Govt. of India and was selected for Marquis Who’s Who: 2017 Albert Nelson Marquis Lifetime Achievement Award. He was nominated by the Institute of Optics at the University of Rochester for Steadman Interdisciplinary Award for Postdocs during Postdoc Appreciation Week from 19.09.2016 to 23.09.2016. He has supervised about 2 PhD theses and 19 MTech theses as well as 8 BTech. He is a life member of the Institution of Engineers (India) and the International Society for Technical Education. Associate Editor of IET Electronics Letters, Associate Editor of IET Journal of Engineering, Punjabi University Patiala, Patiala, Punjab, India Gurpreet Kaur obtained her bachelor’s degree in ECE from IET, Bhaddal, Ropar, India, and a master’s degree from Punjabi University, Patiala, India. She obtained her PhD degree from Thapar Institute of Engineering and Technology, Patiala. Her field of interest is fiber nonlinearity, optical communication system, optical sensor, and optical networks. Presently, she is working as an assistant professor at CU, Mohali. She has published 31 research papers out of which 26 are in international journals (SCI) and 5 in international conferences.

R.S. Kaler is a senior professor in the Department of Electronics & Communication Engineering, Thapar University, Patiala. He is the author and co-author of approximately 193 research journal articles, nearly 111 conference articles, and a few book chapters on various topics related to digital signal processing, microprocessors, and microcontrollers. Thus far, his publications have been cited 1169 times and his H-index is 19 (Source: Scopus). His Google scholar citation is 2091, i10-index is 66, and H-index is 24. He is recipient of more than five research grants from the University Grant Commission, New Delhi; All India Council of Technical Education, New Delhi; and the Ministry of Human Resource Development (MHRD), Govt. of India, New Delhi. His research interests include fiber optics communications, optical networks, optical

About the Editors

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sensors, free space optics, and communication systems. Dr. Kaler currently serves as the deputy director (equivalent to pro vice chancellor of university). He received Shiksha Rattan Puraskar from India International Friendship Society in 2007 and Best Paper Award in International Conference on Information & Communication Technology by IICT. He also got recognition of research work by NASA, USA, in 2002 and was honored, in 2014, as best author (India) under research publications in engineering domain by Career 360 Magazine. He has supervised 14 PhD theses and 37 ME theses. He is a life member of the Institution of Engineers (India) and the International Society for Technical Education. Department of Electronics & Communication Engineering, Thapar University, Patiala, Punjab, India Mohammad Tariqul Islam (Senior Member, IEEE) is currently a professor in the Department of Electrical, Electronic and Systems Engineering, Universiti Kebangsaan Malaysia (UKM), and a visiting professor at the Kyushu Institute of Technology, Japan. He is author and coauthor of about 600 research journal articles, nearly 250 conference articles, and a few book chapters on various topics related to antennas, metamaterials, and microwave imaging with 23 inventory patents filed. Thus far, his publications have been cited 9400 times and his H-index is 44 (Source: Scopus). His Google scholar citation is 15,000 and H-index is 52. He was a recipient of more than 40 research grants from the Malaysian Ministry of Science, Technology and Innovation, Ministry of Education, UKM research grant, and international research grants from Japan, Saudi Arabia, and Kuwait. His research interests include communication antenna design, metamaterial, satellite antennas, and microwave imaging. Dr. Islam served as an executive committee member of IEEE AP/MTT/ EMC Malaysia Chapter from 2019 to 2020 and is a Chartered Professional Engineer (CEng); a fellow of IET, UK; and a senior member of IEICE, Japan. He has received several international gold medals, a Best Invention in Telecommunication Award for his research and innovation, and best researcher awards at UKM. He was a recipient of 2018, 2019, and 2020 IEEE AP/MTT/ EMC Malaysia Chapter Excellent Award. He also won the best innovation award and the Best Research Group

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in ICT niche by UKM, in different years. Dr. Islam was a recipient of the Publication Award from Malaysian Space Agency, for several years. He has supervised about 50 PhD theses and 30 MSc theses, and has mentored more than 10 postdocs and visiting scholars. Dr. Islam has developed the Antenna Measurement Laboratory which includes antenna design and measurement facility till 40 GHz. He was an associate editor of IET Electronics Letter. He also serves as the guest editor of SENSORS and as associate editor for IEEE ACCESS. Department of Electrical, Electronic and Systems Engineering, UKM, Bangi, Malaysia

Chapter 1

Coexistence of Next-Generation Passive Optical Network Stage 2 and 5G Fronthaul Network Rajandeep Singh, Ritika Mahajan, and Ramandeep Kaur

1.1

Evolution from 4G to 5G

There are two segments in 4G networks, the connection between evolved packet core (EPC) and baseband unit (BBU) is called backhaul segment, whereas the connection between BBU and remote radio head (RRH) is called as fronthaul segment. Fronthaul in 4G is an inefficient mechanism because it uses CPRI protocol. The CPRI allows the transmission of data without considering the factor that whether the user traffic is present or not [1]. In 5G networks, a centralized network to connect many devices simultaneously has been designed with redistribution of radio signal functions to new processing elements. All the BBUs are centralized to one location. In the 5G network, the BBU segment is further subdivided into distributed unit (DU), control unit (CU), and active antenna units (AAU). Fronthaul segment is the connection between AAU and DU. The midhaul segment is the connection between DU and CU, and the backhaul segment is the connection between CU and CN [2] (Fig. 1.1). To meet the requirements of 5G such as low latency, broad bandwidth, and low cost, optical networks need to be enhanced. However, these technological advancements bring challenges to the transport network of 5G. The mobile fronthaul link imposes stringent requirements for latency, bandwidth, and cost since it uses Common Public Radio Interface (CPRI) for the data transmission. Fronthaul interface can be constructed in many ways such as copper, microwave, optical fiber, free-space optical communication, and millimeter waves. Among these mediums, optical fiber is preferred due to its capability to handle gigabits with low latency. To meet the

R. Singh (*) · R. Mahajan Department of Electronics Technology, Guru Nanak Dev University, Amritsar, Punjab, India e-mail: [email protected] R. Kaur Department of ECE, Punjabi University, Patiala, Punjab, India © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 S. Singh et al. (eds.), Broadband Connectivity in 5G and Beyond, https://doi.org/10.1007/978-3-031-06866-9_1

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Fig. 1.1 Evolution from 4G to 5G

requirements of 5G such as low latency, broad bandwidth, and low cost, optical networks need to be enhanced. 5G new radio design has some limitations. It requires a large number of active antenna units (AAU) which means a large amount of optical fiber is needed in the network. Moreover, it is not possible to provide a separate wavelength to each antenna unit. This implies that CPRI is quite expensive as it imposes high data rates and low latency requirements. So, it is important to build a cost-effective 5G fronthaul network. Network technology plays an imperative role in building 5G networks. Various competing technologies include point-to-point optical access, Ethernet, passive optical networks (PON), optical transport network (OTN), and free-space optics. Therefore, various optical network technologies are discussed in this work. 5G new radio design has some limitations. It requires a large number of active antenna units (AAU) which means a huge amount of optical fiber is needed in the network. So, it is important to build a cost-effective 5G fronthaul network. Network technology plays an imperative role in building 5G networks. Various competing technologies include point-to-point optical access, Ethernet, passive optical networks (PON), optical transport network (OTN), and free-space optics [1]. Which technology is best among all? Different operators have a different answer to this question as it depends upon their deployment plans and market timing. Due to the huge demand for high data services, higher-speed PONs are needed. Various PON technologies have been discussed in this work which includes TDM-PON and WDM-PON. The mapping of CU/DU/RU to PON has been analyzed in this work.

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Coexistence of Next-Generation Passive Optical Network Stage 2 and 5G. . .

1.2

3

Access Network Technologies

There is a need for broadband access networks as the users traffic as well as their demands have been increasing day by day. Video on demand, multimedia services, online gaming, etc. impose stringent requirements on the access networks. Access networks are the last mile connection between the central office and the user end system. Access networks can be categorized based on the transmission medium used. It includes copper-based access networks, cable modem-based access networks, and wireless networks.

1.2.1

Copper-Based Access Networks

Integrated Services Digital Network (ISDN) is the first broadband access network that belongs to the digital subscriber line (DSL). In these access networks, the data rate for upstream and downstream was just 144 kbps. It limits the transmission distance as well as the data rates. The signal gets degraded, and there are more losses in this medium as compared to others.

1.2.2

Cable Modem-Based Access Networks

One-way broadcast systems in the United States were cable modem access networks. The upstream data range lies between 0 and 45 MHz. The coupling from electrical gadgets degrades the channel properties in this frequency range. A cable modem termination system acts as a central office with which cable modems are connected. The time-division multiplexing technique is used to multiplex individual subscribers.

1.2.3

Wireless Networks

In wireless access networks, the transmission medium is wireless. Wireless access networks include WiMAX, UMTS, GSM, etc. WiMAX (worldwide interoperability for microwave access) provides services for the fourth generation (4G). In the same way, UMTS provides services for the third generation.

1.2.4

Optical Fiber Access Networks

Since optical fiber has low attenuation and high bandwidth and provides long reach, it has been observed that fiber optics-based access networks are the best alternative for future access networks. There are two types of fiber access networks.

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Active Optical Networks (AON)

AON is the point-to-point Ethernet network. It uses active components like Ethernet for the transmission of data to users. In AON, the transmission distance is large and troubleshooting is easy. But it uses more energy and has a high operational cost. Therefore, passive optical networks are coming out as a good candidate.

1.2.6

Passive Optical Networks

A passive optical network (PON) is a point-to-multipoint optical communication system. It uses only passive components. The optical splitters used in PON require no electrical power.

1.3

Advantages of PON

1. Fiber utilization: Efficient use of fiber resources. 2. Future proof: Low maintenance requirements will reduce the operating expenditures. The whole fiber plant is passive since the remote node does not contain any electrical components. Therefore, the upgradation of bandwidth can be easily achieved by replacing the central office components and user’s components. 3. Cable cost: There is a reduction in cable cost as each fiber can be shared with multiple users. 4. Energy consumption: Due to the use of passive components and low attenuation of fiber, energy consumption is low.

1.4

PON Components

The major components in the passive optical network include OLT, ONU, and splitters/combiners.

1.4.1

Optical Line Terminal (OLT)

OLT is the control point for the entire PON. It acts as a service provider endpoint to PON. Using distributed feedback (DFB) laser, OLT transmits the downstream data through a wavelength of 1490 nm. Through the use of a 1310 nm detector at the receiving end, the upstream voice and data traffic are received from ONUs.

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Coexistence of Next-Generation Passive Optical Network Stage 2 and 5G. . .

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Data flow across the optical distribution network (ODN) is controlled by the OLT. OLT does multiplexing using TDM and WDM techniques in the downstream direction and thereby launches the optical signal to the ONUs. Meanwhile, all the user traffic from ONUs is received by the OLT.

1.4.2

Optical Network Unit (ONU)

It is device that converts optical signals to electrical signals at the user’s premises. ONUs are located near the customer premises. A single ONU is connected to multiple users. ONT refers to an optical network terminal. The term ONT is coined by IEEE, whereas the term ONU is coined by ITU-T. ONU provides triple-play services in the gigabit PON (GPON) diagram of ONU. The optical signal is converted into an electrical signal by the PIN/APD photodiode. Then the signal is passed through the low-pass Bessel filter and transmitted to 3R regenerator. Bit error rate (BER), Q-factor, and eye diagram are recorded and observed in the BER analyzer.

1.4.3

Optical Splitter

It is a passive device in the PON and acts as a power divider. It is a bidirectional element that divides the downstream optical signal from OLT to the outputs of the splitter connected with ONU. In the same way, it combines the optical signals from all the ONUs to the single fiber which is connected with OLT. In PON, the splitter acts as a splitter as well as a coupler. In the upstream direction, signals are combined from different ONUs, while signals are splitted in the downstream direction [3]. Figure 1.2 shows the passive optical splitter widely used in passive optical networks. Many parameters affect the working of the optical splitters such as insertion loss, return loss, splitting ratio, isolation, etc. The two widely used splitters include FBT and PLC splitters. For split ratios below 1  4, FBT splitters are preferred, whereas for split ratios above 1  8, PLC splitters are preferred. In PON, a PLC splitter is considered a better option to use.

Fig. 1.2 Passive splitter

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Arrayed Waveguide Grating (AWG)

In WDM systems, AWG is an optical planar device that can be used as a multiplexer as well as a demultiplexer. AWGs multiplex various channels of different wavelengths onto a single fiber in the downstream direction and demultiplex channels of different wavelengths in the upstream direction. Multiple optical channels with different wavelengths can be transmitted over a single fiber because light waves of different wavelengths interfere linearly with each other. This induces minimal cross talk between the channels. Silica-on-silicon- and indium phosphide (InP)-based semiconductors are widely used technologies in the AWG market (Fig. 1.3). According to the position of the fiber nearby the users, the P2MP is categorized as [4]. FTTC (Fiber to the Curb): The optical fiber cable runs from the central office to the street cabinet which is 300 m away from the home or the building (curb). The final connections to the user premises are built through copper cables. FTTB (Fiber to the Building): The optical fiber reaches the boundary of the building, and the final connection to the user is made using other alternatives as in FFTC. FTTN (Fiber to the Node): The optical fiber terminated in the street cabinet which is located within 1000 m from the home or the building (curb). FTTH (Fiber to the Home): PON provides triple-play services over FTTH networks directly from the central office. The optical fiber cable runs from the central office to the home [5] (Fig. 1.4).

1.5

PON Standards

The first PON standard was based on asynchronous transfer mode (ATM) which was termed as ATM-PON or APON. After the introduction of broadband services over PON, the previous standard was renamed to broadband access network (BPON). Figure 1.5 shows the evolution of different standards of PON including the data rates.

Fig. 1.3 Schematic diagram of AWG

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Fig. 1.4 Optical access networks services

Fig. 1.5 Evolution of PON [6]

1.5.1

APON/BPON

The first PON technology that ITU adopted was FSAN’s APON standard. APON is also termed as asynchronous transfer mode passive optical network (ATM-PON) since it provides fiber to the home services that are based on ATM. Due to the higher transmission speeds, broadband services, video distribution, protection, and other functions, this standard was later renamed broadband PON (BPON).

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Fig. 1.6 BPON schematic diagram

It supports downstream data rates of 622 Mbps and upstream data rates of 155 Mbps. 1550 nm is the downstream wavelength, while 1310 nm is the upstream wavelength. The optical fiber length limits to 20 km only. ATM virtual circuits support the communication between ONU and OLT. Disadvantages of APON are listed below: • ATM switches and network cards are very expensive. • The IP datagram will be quashed if any cell is sullied, and the network resources will be used unnecessarily by the remaining cells. • Cell tax is charged on IP packets of different lengths [7] (Fig. 1.6).

1.5.2

EPON

EPON stands for Ethernet PON. They carry Ethernet frames to all ONUs. In the downstream direction, EPON acts as a broadcast network. The ONU accepts only that packet that contains its media access control (MAC) address. In the upstream direction, ONUs send data in the time slots assigned to them which makes EPON a time-shared network. The downstream and upstream wavelengths are 1410 nm and 1310 nm. The disadvantage of EPON is that it requires quality of service (QoS) for real-time traffic.

1.5.3

GPON

To meet the demands of high data rates and more efficient bandwidth, FSAN developed a new standard which was standardized by ITU-T in 2003. It was named Gigabit PON (GPON). It provides a data rate of 2.488 Gbits/s downstream and 1.244 Gbits/s upstream. It provides triple-play services. Figure 1.7 shows the GPON architecture [8].

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Fig. 1.7 GPON architecture

1.6

NGPON2 Technology Options

Different technologies can be used in passive optical networks. The following are some of the technologies that can be used in passive optical networks.

1.6.1

TDM-PON

The transmission medium in PON needs to be synchronized to avoid collisions as it is shared by all the users. Time-division multiple access (TDMA) is used for transmission synchronization. In TDMA, a time slot is assigned to each user and the user transmits data in that time slot only. TDM-PON uses a passive splitter as the remote node which divides the power to different ONUs. PON standards such as APON, BPON, EPON, G-PON, and XG-PON, which have been recently widely deployed, use this architecture [9] (Fig. 1.8).

1.6.2

WDM-PON

In WDM-PON, each user can access the entire bandwidth, and there is no need to share the bandwidth as in TDM-PON. Multiple wavelengths are passed through a single fiber which further improves the capacity of the medium. Since each home receives its wavelength, these networks are secure and scalable [10]. Figure 1.9 shows the block diagram of the WDM-PON.

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Fig. 1.8 TDM-PON architecture

Fig. 1.9 WDM-PON architecture

1.6.3

TWDM-PON

TWDM-PON is time wavelength division multiplexing. TWDM-PON is a combination of TDM and WDM-PON. In this work, an NGPON2 setup has been made which uses the TWDM technology. In the downlink direction, WDM is used, while in the upstream direction, TDM is used. The advantage of using this technology is the use of the same optical distribution network (ODN) and splitters as the previous PON standards [11]. TWDM-PON stacks multiple XG-PONs. ONUs contain tunable transmitters and receivers. The transmitters are tunable to upstream wavelengths while receivers to downstream wavelengths. In TWDM-PON, multiple wavelengths pass through the WDM feeder fiber, and the power splitter broadcasts it to all the users. ONUs contain tunable transmitters and receivers. The transmitters are tunable to upstream wavelengths while receivers to downstream wavelengths.

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Literature Review

To build a cost-effective 5G fronthaul network, different authors discussed various optical access technologies for building the network considering the factors of low latency, broadband width, low cost, and low power. Therefore, optical networks need to be enhanced and improved to meet the requirements of 5G. The performance of coherent WDM-PON technology was analyzed by W. Shbair et al. The experimental setup shows that 800 Gbps bidirectional mobile fronthaul and mobile backhaul which is suitable for 5G have been achieved using 100 Gb/s per wavelength-based coherent WDM-PON technology [12]. The pros and cons of different optical technologies were presented by Muhammad Waqar et al. as shown in Table 1.1 [13]. Zhou et al. has presented how mobile PON is merging TDM-PON with mobile and PON scheduler [14]. The bandwidth can be shared with other remote sites with the use of this interface. The increase in bandwidth is due to the new physical layer split and modulation decoding.

Table 1.1 Optical transport technologies proposed for FH networks [13] Optical technology TDM-PON [14]

WDN-OTN [15]

Nonhierarchical and point-to-point WDM [16] SCM-DWDM [10] DWDM-PON, coherent optical OFDM [17] Uni-PON, OFDMWDM [18] DWDM [19] Multicore fiber [20] Photonics-aided amplification [21]

Contribution For the cost-effective PON, it improves the performance of the network without additional scheduling delay. Also, it increases the fronthaul bandwidth by ten times over CPRI Provide solutions to connect RRHs with BBU in dense areas to achieve speeds from 10 Mbps to 1 Gbps Improve the transparency and network cost in centralized base stations High spectral efficiency and throughput Reduces the cost due to the utilization of existing PON infrastructure and small channel spacing methods Multiplexed and transported 14 wavelengths per fiber successfully while maintaining the BER within limits Reduces network complexity Proposed MIMO-based transmissions to achieve better performance and capacity at low inter-core cross talk Improves throughput, reduces cell-edge user interferences and SNR. BER is reduced 2.5 dB times

Limitation Scheduling causes an increase in the FH interface and overhead at switches. There will be an infinite delay if more than 18 RRUs operate simultaneously The employment cost increases with the use of WDM-OTN and colored fiber Increases installation cost. Traffic monitoring is required to retain the network performance Increase the cost Expensive and complex

Increases the complexity and causes high attenuation in the FH network SNR increases and expensive Increases the implementation complexity and cost of the network High capital expenditure (CAPEX) due to the complex setup for fiber transmission

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The architecture of the 5G fronthaul network has been discussed by Yan Jiang et al. In their work, they also compared the working of different 5G technologies and analyzed the cost calculation model. The result states that a cost-effective 5G network can be deployed considering the appropriate DU location and DU concentration [2]. According to Zhang et al., the N25G high-speed WDM-PON technology fulfills the demands of the 5G fronthaul network that includes low latency, high data rate, and broad bandwidth. Also, for simple operation and low cost, it is suggested to use C-RAN with WDM-PON technology [22]. To increase the optical reach up to 50 km and expanding the customer coverage, Super-PON is the upcoming technology as discussed by Claudio DeSanti et al. This is achieved by using many possible methods like wavelength routing, optical amplification, TDM-PON, etc. [23]. Sarvesh Bidkar et al. proposed that in 5G radio access networks, radio signals can be transmitted by using optical technology TDM-PON. TDM-PON provides costeffective and efficient mechanism for the transmission of signals. TDM-PON latency requirements have been analyzed. TDM using cooperative DBA (Co-DBA) and Cooperative Transport Interface, TDM-PON latency, and bandwidth requirements can be achieved [24]. The high demands of fifth-generation networks make it necessary to think about new ideas and technologies to enhance wireless communication networks. The requirements of 5G networks have been discussed by Akyildiz et al. Various technologies, their potentials, and limitations have been examined by Akyildiz et al. [25], Federico Boccardi et al. [26], Ekram Hossain, and Monowar Hasan [27]. Also, the current research activities are discussed by the authors. The handover reduction mechanism has been proposed by Xinbo Wang et al. They presented a new virtualized CRAN architecture over TWDM-PON with virtual network resources in PON, RUs, and DUs. The handover reduction optimization problem is modeled considering two factors: first when future information is known and second when future information is unknown. The throughput of cell edge increases with the use of V-CRAN. The number of handovers also reduces with its usage [28]. Eduardo Saia Lima et al. demonstrated the design of the 5G new radio photonically amplified fronthauls and backhauls. Their implementation and experimental performance have been reported. It aims to utilize the fiber optic links for the amplification of data signals in the optical domain as well as their transmission. Photonics-assisted RF amplification (PAA) reduces the power requirements. Experimentally, for a 10-Gbit/s signal, 19-DB baseband amplification and 26-dB photonics-assisted RF gain for frequencies up to 50 GHz have been achieved. For 256-QAM signals, PAA also increases the throughput to 13.5 Gbit/s which is 12.3 times higher than that of CRoF [29]. A two-stage optimization framework and architecture have been proposed for converged 5G infrastructure by Anna Tzanakaki et al. The integration of wireless and optical network for a common transport network is termed the converged 5G infrastructure. The first stage focused on minimizing the capital expenditure. In the

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second stage, for the allocation of 5G services, the suitable processing modules are identified. The performance analysis of the proposed framework has been done using various network technologies such as passive optical networks, millimeter wave, etc. [30]. The technical advancements in new radio 5G networks impose stringent requirements on the fronthaul transport network. Therefore, optical links are a good option to build fronthaul links. But this will lead to a reduction in the fiber length to a few kilometers and an increase in the cost. The performance of passive optical network links with the optimal locations of EDFA has been evaluated by Muhammad Waqar et al. Various performance indicators such as signal power, dispersion, and signal-tonoise ratios were measured, and the proposed network was evaluated. They also demonstrated the optimized locations to add the amplifiers for long-distance communications [31]. Björn Skubic et al. in their work deployed a 5G radio network for fixed wireless access (FWA) to meet the requirements of future fixed broadband access. 5G fixed wireless access is a good alternative to fixed broadband services. Various optical network technologies and requirements of different radio access networks have been analyzed. They also stated that the coarse wavelength division multiplexing (CWDM) and the 10G passive optical networks (XG-PONs) are the most costeffective solutions for higher-layer split. XGPONs support fiber to the home (FTTH), whereas CWDM provides low latency rates. However, point-to-point (PtP) or PtP-WDM is required for lower-layer split [32]. The power consumption of ring topologies with time and wavelength division multiplexed passive optical network (TWDM-PON) has been analyzed by Bhargav Ram Rayapati et al. [33] in their work. To transit ONU to sleep mode, two scheduling algorithms, namely, fixed and load adaptive sequence arrangement (LASA), were used to reduce the power consumption in the ring topologies. A maximum of 18% reduction in power consumption with a fixed polling sequence and 9.27% reduction in power consumption with LASA polling sequence is observed. When the cycle time lies between 1 and 2 ms, the LASA polling sequence shows better power conservation than the fixed polling sequence. For average power consumption per ONU, the average power consumption of various ONUs at different time slots has been computed. In their present work, they have analyzed and considered the static TDMA. Anliang Liu et al. in their work proposed a low-cost WDM-RoF system for the next-generation 5G communication. This system consists of a central station, a subcentral station, and a base station. According to the authors, the integration of this system with the WDM-PON has reduced the construction cost of the RoF system. The simulation has been performed utilizing OptiSystem software. The simulated results have verified the feasibility of the WDM-RoF system with a 20-GHz subcarrier. The chromatic dispersion effects have also been reduced with the use of the RoF system. Centralized management of the base station led to the decrease in the power consumption as well as the complexity of the system [34].

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Authors in their work proposed architecture for broadband Internet services and fifth-generation mobile communications. A hybrid analog radio over fiber (ARoF) and next-generation (NG) wavelength division has been multiplexed with the passive optical network (WDM-PON). With the use of a dense WDM channel frequency grid (50GHz), various possible A-RoF system implementations into the PON segment have been researched. They researched the possible A-RoF system implementations into PON’s segment with a dense WDM channel frequency grid (50 GHz) [35].

1.8

Design and Performance Investigation of a PON-Based System for 5G Fronthaul

PON-based system for 5G fronthaul is practiced, and the performance of the system is analyzed. The 5G is integrated with the NGPON2 system. NGPON2 for power split 128 is used in the simulation setup. For 5G, a WDM transmitter with eight output ports each with a wavelength of 10 Gbps is used to send the downstream signal to the 5G tower. The results for both 5G and NGPON2 are recorded using a BER analyzer. The Q-factor value of 51.7644 is achieved at a power of 2dbm in star based next-generation passive optical network (NGPON2) with 40 Gbps data rate using different split ratios. Q-factor and bit error rates for different split ratios are compared, and alternate solutions are provided to enhance the performance of the system. The Q-factor and bit error rate for split 16,32,64 and 128 using PIN photodiode and avalanche photodiode (APD) are recorded and compared for power split 16,32,64 and 128 in the downstream direction. Also, the results for power split 8 in the uplink direction are recorded. It is observed that APD gives much better results than PIN photodiode for 128 power split. Wireless mobile communication has seen tremendous growth over the past few decades. With the increasing demands of users, many operators have started to build 5G networks. The demands that need to be fulfilled include high data rates, broad bandwidth, and low latency rates. These can be achieved by improving the existing cellular network architecture. This shows that there is a need to enhance the transport network. Various methods are discussed in this chapter to improve the transport network. Mobile wireless communication started with the announcement of first generation in the 1980s. After 1G, the demands of users started increasing which led to the development of various wireless communication standards. The first-generation (1G) services offered analog voice communication. Then, the second generation (2G) offered digital voice communication and allowed text messaging. To provide data to mobile users, third generation offered mobile broadband that included multimedia with text messaging. The need for multimedia services kept on increasing rapidly and thereby led to the development of 4G [36]. Currently, the increasing demands have made the operator to start building 5G networks. In this chapter, the behavior of various optical spectrums for the uplink and downstream signals is analyzed.

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System Architecture for Integration of PON and 5G Fronthaul

The integration of 5G with PON consists of a central office, optical network unit, optical distribution network, and 5G tower. Block diagrams of the setups have been explained in detail in the following sections.

Central Office Architecture Figure 1.10 shows the simulation setup of the central office for the integration of 5G with NGPON2. For NGPON2, four transmitters with a downstream wavelength of 1596 nm with frequency spacing of 0.8 nm are stacked and sent to the wavelength division multiplexer (WDM). NGPON2 provides a data rate of 40 Gbps. The data is sent to the ideal multiplexer from where it is fed into the optical fiber. For 5G downlink, a WDM transmitter with eight output ports and frequency 193.1 THz is used. The frequency spacing is 0.1 THz. Also, a CW laser array with eight output ports and a frequency of 193.1 THz is used. Both WDM transmitter and CW laser array are multiplexed, and the data is transferred to the ideal multiplexer. The laser array does not carry any data which means only light is being sent. Therefore, the three inputs of the ideal multiplexer include data from NGPON2 transmitters, 5G transmitters, and CW laser array. These are passed through the optical fiber of length 20 km. The circulator is used to receive the uplink data from NGPON2 and 5G towers.

Fig. 1.10 Simulation setup of central office

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Optical Distribution Network (ODN) Figure 1.11 shows the simulation setup of ODN. The fiber Bragg grating having frequency 193.1 THz with bandwidth 3.73 THz is used. Therefore, the NGPON2 signal gets passed through it, whereas it reflects the data coming from the WDM transmitter. The NGPON2 downstream data is fed to the WDM demultiplexer for further processing. The reflected data is demultiplexed using WDM demux with a split ratio of 1:16. After demultiplexing the data, the power combiner combines the individual wavelength of the WDM transmitter with a light signal.

Optical Network Unit (ONU) Figure 1.12 shows the simulation setup for NGPON2 ONU. The data from the demultiplexer is fed to the power splitters with split 128. Then the avalanche photodiode (APD) is used which converts the optical signals to electrical signals. The optical signal is then passed through the Bessel filter. The signal is then received and analyzed using a BER analyzer. Through the BER analyzer, Q-factor and bit error rate values are recorded. This NGPON2 with a 40 Gbps bit rate is capable of transmitting the data to 512 ONUs. Also, optical visualizers are used to analyze the various spectrums at the receiving end.

Fig. 1.11 Optical distribution network

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Fig. 1.12 Block diagram of ONU

Simulation Setup of 5G Tower Figure 1.13 shows the simulation setup for the 5G tower. The data from the exchange office is fed into the reflective fiber bidirectional. It reflects the 5G downstream signal and the signal is received through photodetector APD. The one that is passed through it is fed into the reflective semiconductor optical amplifier (RSOA). The part which only contains light can be used to modulate another signal, and the other part which carries data is used for uplink.

Block Diagram of Signal from 5G Tower to Exchange Office The signal from the 5G tower gets multiplexed and passes through fiber of length 20 km. Then it gets demultiplexed, and the data is received using photodetector APD which converts the optical signals to electrical signals. The results are calculated using a BER analyzer (Fig. 1.14).

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Fig. 1.13 Block diagram of the 5G tower

Fig. 1.14 Block diagram of signal from 5G tower to exchange office

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Results and Discussions

Figure 1.15 shows the BER vs transmitted power graph for 5G downlink. The power varies from 20 dB to 0 dB. It is observed that the BER improves as the power increases. It is quite low at power 6 dB. Figure 1.16 shows the Q-factor vs transmitted power for 5G downlink. The value of the Q-factor increases with the increase in power and is maximum at 2 dB. Figure 1.17 shows BER vs transmitted power graph for 5G uplink. The BER decreases with the increase in power values and is lowest at 0 dB. Figure 1.18 shows Q-factor vs transmitted power graph for the 5G uplink. The BER decreases with the increase in power values and is lowest at 0 dB. Figure 1.19 shows BER vs transmitted power graph for the NGPON2 downlink. The BER decreases with the increase in power values and is lowest at 5 dBm power. Figure 1.20 shows Q-factor vs. transmitted power graph for the NGPON2 downlink. The Q-factor increases with the increase in power values and it is highest at 5 dBm power. Figures 1.21 and 1.22 show the eye diagram for 5G downlink and uplink. Figure 1.23 shows the eye diagram for NGPON2 downlink. Figures 1.24 and 1.25 show the optical spectrums of downstream signal to first 5G tower and downstream signal received at first 5G tower diagram for NGPON2 downlink. Figures 1.26 and 1.27 show the optical spectrums of signal available for remodulation and signal after remodulating the first 5G tower. Figure 1.28 shows the optical spectrum of the 5G upstream signal at OLT.

Fig. 1.15 BER vs transmitted power for 5G downlink

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Fig. 1.16 Q-factor vs transmitted power for 5G downlink

Fig. 1.17 BER vs transmitted power for 5G uplink

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Fig. 1.18 Q-factor vs transmitted power for 5G uplink

Fig. 1.19 BER vs transmitted power for NGPON2 downlink

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Fig. 1.20 Q-factor vs. transmitted power for NGPON2

Fig. 1.21 Eye diagram for 5G downlink

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Fig. 1.22 Eye diagram for 5G downlink

1.9

Conclusion

In this work, the feasibility of the integration of 5G with NGPON2 is shown in the simulation setup. Four transmitters each with a data rate of 10 Gbps are multiplexed and sent through the optical fiber. The downstream wavelength is 1596 nm, whereas the uplink wavelength is 1524 nm. The results for the NGPON2 downlink for APD photodiode are recorded and observed through a BER analyzer. Also, for 5G downlink, a WDM transmitter with eight output ports each with a data rate of 10 Gbps is transmitted. The downstream wavelength is 193.1 THz with a frequency spacing of 0.1 THz. The 5G signal is received at the 5G tower. Q-factor of 51.7644 is achieved at the 5G first tower. The Q-factor for 5G uplink gives an acceptable value. In this way, both 5G and NGPON2 data are received through the shared infrastructure.

Fig. 1.23 Eye diagram for NGPON2 downlink

Fig. 1.24 Downstream signal to first 5G tower

Fig. 1.25 Downstream signal received at first 5G tower

Fig. 1.26 Signal available for remodulation

Fig. 1.27 Signal after remodulating first 5G tower

Fig. 1.28 Upstream signal of 5G at OLT

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Dr. Rajandeep Singh received his BTech (ECE) from Guru Nanak Dev Engineering College, Ludhiana, India, in 2009. He received his MTech (Communication Systems) from Guru Nanak Dev University, Amritsar, in 2011 and received the PhD degree from Guru Nanak Dev University, Amritsar, India, in 2021. Dr. Rajandeep Singh is currently working as Assistant Professor of Electronics Technology at Guru Nanak Dev University, Amritsar, India. Dr. Rajandeep Singh is associate editor of the Journal of Engineering (IET). He has authored 12 papers in SCI journals, 17 papers in international conferences, and 6 papers in national conferences. His area of research is optical amplifiers, passive optical networks, and machine learning. Er. Ritika Mahajan holds an MTech (ECE), with specialization in communication system, from Guru Nanak Dev University, Amritsar. Her master’s thesis is on integration of 5G technology with passive optical networks. Dr. Ramandeep Kaur is currently working as an assistant professor in the Department of ECE, Punjabi University, Patiala, India. She has received her BTech (ECE) degree from Guru Nanak Dev Engineering College, Ludhiana, India, in 2009. Then, in 2011, she received her ME (ECE) degree from Thapar University, Patiala, India. She received PhD from Punjabi University, Patiala, India, in 2021. She is the associate editor of the Journal of Engineering (IET). Ramandeep has authored 16 papers in Science Citation Indexed journals. She has presented 10 papers at international and national conferences. She has guided 18 students in their MTech Theses. Her areas of research are passive optical networks, optical communication, and machine learning.

Chapter 2

Design of Wideband MIMO Patch Antenna Array for Millimeter-Wave-Based 5G Wireless Communications Mandeep Singh and Simranjit Singh

2.1

Introductions

The modern lifestyle is fully changed with the commencement of wireless communication. The advanced use of data starving devices like computers, mobiles, tablets, and sensors leads to a shortage in bandwidth [1, 2]. Due to the lack of frequency spectrum bandwidth, there is a requirement of high-frequency, wide bandwidth for higher data rates. To solve such problems, millimeter-wave (mm-wave) frequency bands are recommended by the International Mobile Telecommunications (IMT) for a fifth-generation (5G) mobile application. The 5G technology will utilize millimeter-wave bands to provide large data abilities for transferring multi-Gbps [3, 4]. In various developed countries like the USA, China, Japan, etc., many research groups are intensively forwarding toward 5G technologies. Recently, the Federal Communications Commission (FCC) settled its first 5G band auction for 24 GHz and 28 GHz band spectrum, and in the future, FCC will auction the higher 3 7 GHz, 39 GHz, and 47 GHz frequency bands for future wireless communications [5]. AT & T and Qualcomm the major giants in wireless technology are testing the wireless equipment at 24 GHz [6, 7], so world is moving forward to develop new devices which support these high-frequency bands. Antenna plays an important role for wireless devices, so there is a need to develop a cost-effective antenna that can support high-frequency bands for next-generation technology. A major issue for high-frequency wireless communication, however, is the path loss owing to low wavelength and environmental circumstances that can be overcome with the use of fully developed and effective MIMO patch antenna [8]. MIMO

M. Singh (*) · S. Singh Department of Electronics and Communication Engineering, Punjabi University Patiala, Patiala, Punjab, India © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 S. Singh et al. (eds.), Broadband Connectivity in 5G and Beyond, https://doi.org/10.1007/978-3-031-06866-9_2

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antennas can deliver several benefits for future networks because it is single-chip antenna that can be operated at wideband frequencies with high gain. Moreover, it can also minimize the multiple path loss and interference between signals. MIMO patch antenna has low-profile, lightweight, and simple assembly to ensure reliability, flexibility, and high efficiency. Despite the reality that the MIMO antenna has countless benefits, in the current situation, there are some enormous downsides. Similarly, the structure must be reliable with future wireless frameworks, and there must be little mutual coupling due to the closeness of radiating components to the ordinary substratum. MIMO has a channel solution for non-line of sight track circumstances and reduces the loss of distortion and various way losses [9–13], so there is a need to develop such devices which also do not have a bad impact on human body. Recently, researchers proposed mm-wave antennas for next-generation wireless applications, although some researchers achieved the efficient bandwidth and gain but on the cost of complexity and cost of design where several layers of substrate are implemented [14–17]. S. Faleh [18] proposed a wideband MIMO antenna but at the cost of low gain, and Hala M. Marzouk [19] presented a dualband MIMO antenna with high-performance parameters, but the proposed antenna has large size. M.S. Sharawi [20], H. Aliakbari [21], and Md. Hassan [22] proposed patch antennas suffer from low bandwidth and low gain which need to be increased for next-generation wireless communications. M. I. Khattak [23] proposed a patch antenna array, but the antenna had narrow bandwidth. So, there is need to develop a low-profile patch antenna that can cover the desired bands, i.e., 24 GHz and 28 GHz. To achieve this aim, in this work, a patch antenna having low profile and wide bandwidth is designed, optimized, and tested for next-generation wireless applications. The early reported antennas suffer from low gain, low efficiency, narrow bandwidth, and large size issues, as discussed in the literature. Some researchers successfully attain much better performance but at high cost and more system complexity. Some designs are not practically possible to integrate within devices. So, in this research, a novel approach to design a wideband millimeter MIMO antenna is proposed. First, a new patch antenna is designed and optimized by using the PSO technique which covers 28 GHz frequency, in a 5G band. The DGS is deployed across the ground of antenna to achieve wider bandwidth and higher gain. Furthermore, the low-profile 2
2 MIMO antenna is designed, and the performance of such antenna is investigated to validate the diversity of MIMO antenna system. This research paper is divided into sections as discussed below. In Sects. 2.2 and 2.3, the mathematical modeling and optimization of the proposed antenna are done. In Sect.2.4, a 2
2 MIMO patch antenna is designed by using an optimized patch antenna element, and also, the various performance parameters of the MIMO antenna are discussed and compared with the recently reported MIMO patch antenna for next-generation wireless communications (Table 2.1).

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Table 2.1 Optimized parameters of proposed antenna using PSO Rectangular patch antenna

2.2

Parameters

Initial value

Pw (width of patch) PL (length of patch) GL (length of ground plane) Fw (width of feedline) SR (diameter of ground slot)

4.40 3.00 20 1.23 3

Decision space (minimum to maximum) 7 15 2 7 0 20 1 5 2 6

Optimized value 8.50 3.54 17.81 2.68 5.45

Mathematical Modeling of Patch Antenna

A rectangular patch antenna is designed by using the transmission line model. The performance of an antenna depends upon its dimensions of antenna. So, the dimension of an antenna is computed by using below equations [24]. The width of the rectangular patch (PW) is computed by using: Pw ¼

1 pffiffiffiffiffiffiffiffiffi 2
f r
μ 0 ε0

rffiffiffiffiffiffiffiffiffiffiffiffi rffiffiffiffiffiffiffiffiffiffiffiffi 2 2 v0 ¼ Er þ 1 2
f r Er þ 1

ð2:1Þ

where εr is the substrate material’s dielectric constant, fr is the resonating frequency, and vo is the velocity of light. To calculate an effective dielectric constant (εreff ) of the substrate material having height h, the following equation is used: εreff

  h εrþ1 εr1 ¼ þ 1 þ 12 2 2 Pw

ð2:2Þ

Due to fringing effects, the length of the rectangular patch appears wider than the actual length of PL. The length increase due to fringing impact is calculated using Eq. (2.3). Therefore, the length rise ΔL is calculated by:   ðεreff þ 0:3Þ
PhW þ 0:264 ΔL    ¼ 0:412 h ðεreff  0:258Þ
PW þ 0:8

ð2:3Þ

h

The actual length (PL) of the patch antenna is calculated by: PL ¼ L þ 2ΔL

ð2:4Þ

λ  2ΔL 2

ð2:5Þ

PL ¼

The transmission line within Zo impedance is performed using the following equations, where the conducting line has FW width and the substrate material

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thickness is h. The εre is the zero-frequency value provided by equation of the efficient dielectric constant of conducting line [25]: εre ¼

  10 ab εr þ 1 ε r  1 þ 1þ 2 2 u

ð2:6Þ

Here, a and b are given by Eqs. (2.7) and (2.8): (  u 2 )  

u4 þ 52 1 u 3 1 a¼1þ þ ln 1 þ ln 18:7 18:1 49 u4 þ :432 b ¼ 0:564

 :053 εr  0:9 εr þ 0:3

ð2:7Þ ð2:8Þ

The realization of the characteristic impedance Zo is given below: pffiffiffiffiffi When Z 0 εre  89:91, that is, A > 1:52: 8 exp ðAÞ FW ¼ h exp ð2AÞ  2

ð2:9Þ

pffiffiffiffiffi When Z 0 εre  89:91, that is, A < 1:52: 

 2 ε 1 FW Q :61 B  1  ln ð2B  1Þ þ r ln ðB  1Þ þ :39  ¼ h 2εr εr

ð2:10Þ

is given by Eqs. (2.9) and (2.10) and the value of B and A is given by Eqs. (2.11) and (2.12): B¼ A¼

60 pffiffiffiffi Z 0 εr



n o1 :11 z 0 εr þ 1 2 εr  1 þ 0:23 þ 60 εr 2 εr þ 1

ð2:11Þ ð2:12Þ

The overview of patch antenna is shown in Fig. 2.1. The various dimensions of millimeter-wave-based patch antenna are calculated for 28 GHz frequency by using Eqs. (2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 2.10, 2.11, and 2.12) which are listed in Table 2.2. The dimensions calculated by using given equations will not have high accuracy for resonating frequency, so further the patch and ground dimensions are optimized by using parametric analysis of CST software.

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Fig. 2.1 Overview of proposed rectangular DGS millimeter patch antenna: (a) top view and (b) bottom view Table 2.2 Dimensions of proposed antenna and optimized antenna (mm) Parameter of antenna Length of patch (PL) Width of patch (PW) Length of feedline (FL) Width of feedline (FW) Width of the ground (GW) Length of ground (GL) Diameter of circular slot inside ground surface (SL) Length of substrate (sL) Width of substrate (sw)

2.3

Proposed antenna 3 4.40 11.50 1.23 20 20 4 20 20

Optimized antenna 3.5440 7.4247 11.2301 4.6808 20 17.8100 3.4484 20 20

Optimization of Millimeter-Wave Antenna

The performance of proposed antenna is optimized by using PSO technique of the CST optimizer. The various dimensions of patch, slot, and ground plane are optimized to improve the performance of the antenna in terms of reflection coefficient (dB), bandwidth, and gain. To command the PSO algorithm in the simulator, 25 particles and 20 iterations with a total of 401 evaluations are used in the CST optimizer as listed in Table 2.1 [26] [27]. PSO optimization algorithm is applied over the range of frequency to optimize the performance of the proposed antenna in the millimeter regime. The objective

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M. Singh and S. Singh

Fig. 2.2 Overview of fabricated optimized rectangular DGS millimeter wave patch antenna (a) Top view (b) Bottom view

function of the algorithm is to get good results in terms of bandwidth, gain, and return loss as given by Equation (2.13). The results from simulations, optimization, and experimentations of proposed antenna are presented in this section which is measured on VNA in antenna lab of IIT Delhi: Objective function ¼ max ðRL þ B:W þ G Þʋ

ð2:13Þ

where RL is return loss, B.W is bandwidth, and G is gain of antenna. After optimization of proposed antenna, it is fabricated by using the photolithography process as shown in Fig. 2.2. As per the requirement of acceptable performance, the return loss should be less than 10 dB for desired resonating frequency. In Fig. 2.3, it is observed that the proposed antenna is resonating at 27.76 GHz with a return loss of 23.45 dB and having 21.78–28.45 GHz wide bandwidth. To improve the performance and to make the antenna resonance toward the desired frequency within wide bandwidth and high gain, the PSO technique is used. PSO algorithm optimizes the structure of the patch antenna to attain desired 28 GHz frequency. After optimization of antenna, it is noted from Fig. 2.3 that the bandwidth of antenna is increased and antenna starts resonating at 27.67 GHz frequency with a reflection coefficient of 35.04 dB and covers effectively the future 5G bands like 26 GHz and 28 GHz. Furthermore, for the experimental validation of results, the optimized patch antenna is fabricated by using Rogers RT/Duroid 5880 substrate material. Also, the fabricated antenna is experimentally tested by using VNA. It is noted that the proposed antenna is resonating at 27.71 GHz with a return loss of 16.86 dBi. There is some difference between the simulated return loss and experimentally measured return loss of proposed antenna due to cable and connector losses. Apart from the bandwidth of 23.84 GHz to 28.75 GHz concerning resonating bands, the VSWR for resonating band is less than 2, which indicates the proper utilization of input power. So, the optimized antenna is efficiently covering 26 GHz and 28 GHz bands for future wireless applications. In Fig. 2.4, the realized gain and directivity are plotted over frequency for proposed and optimized patch antenna. The gain and directivity of the proposed patch antenna are 6.41 dB and 6.78 dB, which is enhanced to 6.91 dB and 7.21 dB,

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-5

Return loss (dB)

-10 -15 -20 -25 -30 RMPA Millimeter wave antenna Proposed antenna (Experimentally Measured) Optimized Proposed antenna

-35

20

22

24

26

28

30

Frequency (GHz)

Fig. 2.3 Experimentally measured return loss versus frequency for optimized patch antenna

8 7

dB

6 5 4 3 Directivity (dB) of Proposed optimized Antenna Directivity (dB) of Proposed patch Antenna Gain (dB) of Proposed Antenna Gain (dB) of Proposed optimized patch Antenna

2 1 20

22

24 26 Frequency (GHz)

28

30

Fig. 2.4 Gain and directivity versus frequency for proposed and optimized antenna

respectively, at 28 GHz frequency by achieving proper impedance matching between the input and output source. Also, it is noted from the plot of antenna that it is covering 26 GHz, 5G bands. It can be seen that the gain and directivity at these bands are enhanced from 6.35 dB and 6.55 dB to 7.02 dB and 7.32 dB, respectively.

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M. Singh and S. Singh

Efficiency=(Value X100)%

0.95 0.90 0.85 0.80 0.75 Radiation efficiency of optimized antenna Radiation efficiency of Proposed antenna Total efficiency of optimized antenna Total efficiency of proposed antenna

0.70 0.65 20

22

24 26 Frequency (GHz)

28

30

Fig. 2.5 Radiation and antenna efficiency versus frequency of proposed and optimized antenna

330

10

Gain (dB)

-10

30

0 300

-10

60

-20 -30 -30

270

90

-20 -10 0 10

120

-30 -30

150 180

(a)

300

H-Plane

60

270

90

-20 0 10

210

30

-20

-10 240

330

10

Gain (dB)

0

0

E-Plane

0

240

120 210

150 180

(b)

Fig. 2.6 Radiation pattern of proposed optimized antenna at 28 GHz: (a) optimized antenna for E-plane and (b) optimized antenna for H-plane

The impedance throughout the resonating frequency band is close to 50 Ohm, which indicates the efficient transmission of radiations from patch antenna. The efficiency is another concern for the patch antenna performance at such high frequency. The radiation and antenna efficiency of the optimized patch antenna is plotted in Fig. 2.5. The optimized patch antenna has 96.01% radiation efficiency and 96.94% antenna efficiency at 28 GHz resonating frequency band, which is highly desirable for millimeter-wave applications. In Fig. 2.6, the radiation patterns of the E-plane

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and H-plane are measured at 28 GHz frequency, respectively. It is observed that the optimized antenna is providing good results and efficiently transmitting the radiations at the broadside.

2.4

Design of MIMO Patch Antenna

To increase the data rates and reliability of wireless communication systems, a 2
2, i.e., row
column, or 4
4, i.e., 4 transmitting
4 receiving, MIMO patch antenna is designed by using the proposed optimized patch antenna element. MIMO antenna has several advantages over single antenna element like it minimizes the fading loss and multipath loss of signals and increases the QoS. We have designed four antenna elements that are designed on a single substrate by using common DGS. The top and bottom view of the MIMO patch antenna is shown in Fig. 2.7. Port 2

Port 1

Port 3

(a)

Port 4

(b)

(c)

Fig. 2.7 Overview of proposed 2
2 DGS MIMO patch antenna array: (a) top view, (b) bottom view, and (c) 3-D view

40

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M. Singh and S. Singh

Results and Discussions

The S-parameters of each antenna element of MIMO antenna are calculated. Here for easy demonstration, the reflection coefficient and transmission coefficient are presented in Figs. 2.8 and 2.9, respectively. In Fig. 2.8, the reflection coefficient of each antenna element is measured from the simulated results where each antenna element is resonating at 27.03 GHz with 36.04 dB return loss. Each antenna element has the same character because every element in MIMO has a symmetrical structure. The proposed MIMO antenna has achieved a bandwidth of 40.70%. In Fig. 2.9, the transmission coefficient has values less than 17 dB between all antenna elements, which indicates that the mutual coupling between antenna elements is low. It is also noted that mutual coupling between Port 1 and Port 4 and Port 2 and Port 3 is high as compared to other ports (Figs. 2.10 and 2.11). The directivity and gain of the proposed MIMO antenna are revealed in Fig. 2.12, which shows that the suggested MIMO antenna has achieved maximum directivity of 9.18 dB and gain of 8.76 dB, which makes it a good candidate for higherfrequency applications. The diversity gain and envelope connection coefficient (ECC) are investigated to check the diversity capacity of the 2
2 MIMO antenna array. The ECC is used to discover the relationship between symmetrical antenna elements on the same substrate and can be calculated by using Eq. (2.14). The values of ECC between the symmetrical component must be below to get higher estimation of diversity between the MIMO antenna elements. It is based on S-parameters and takes into record the shape of radiation example, polarization,

Reflection coefficient (dB)

-10

-15

-20

-25

S11 S22 S33 S44

-30

-35

-40 20

22

24

26

28

Frequency (GHz) Fig. 2.8 Reflection coefficient versus frequency for MIMO antenna

30

32

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Design of Wideband MIMO Patch Antenna Array for Millimeter-Wave-Based. . .

41

Transmission Coefficient (dB)

-15

-20

-25

-30

-35

S12 S21 S31 S32 S41

-40

-45 20

22

24

26

28

30

32

Frequency (GHz) Fig. 2.9 Transmission coefficient versus frequency for MIMO antenna

2.0 VSWR MIMO Port 1 VSWR MIMO Port 2 VSWR MIMO Port 3 VSWR MIMO Port 4

1.8

VSWR

1.6

1.4

1.2

1.0 20

22

24

26

28

Frequency (GHz) Fig. 2.10 VSWR versus frequency for MIMO antenna

30

32

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M. Singh and S. Singh

Efficiency =(Value x100)%

0.90

0.88

0.86

0.84 Radiation efficiency for antenna 1 Radiation efficiency for antenna 2 Antenna efficiency for antenna 1 Antenna efficiency for antenna 2

0.82

0.80 22

24

26

28

30

32

Frequency (GHz) Fig. 2.11 Antenna and radiation efficiency versus frequency for MIMO patch antenna

10.0 9.5

dB

9.0 8.5 8.0 Gain (dB) Directivity (dB) Diversity Gain (dB)

7.5 7.0 20

22

24

26

28

30

32

Frequency (GHz) Fig. 2.12 Directivity, gain and diversity gain versus frequency for MIMO antenna

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0.0035 0.0030 ECC for port (1,2) ECC for port (1,3) ECC for port (1,4)

0.0025

ECC

0.0020 0.0015 0.0010 0.0005 0.0000 -0.0005 20

22

24

26

28

30

32

Frequency (GHz) Fig. 2.13 ECC versus frequency for MIMO antenna

and relative phase between two antenna elements in a MIMO system. From Fig. 2.13, the values of S12, S13, and S14 are less than 0.001, which is adequate for the chipping away at two independent antennas on a single substrate [28]. The diversity gain is used to realize the diversity of MIMO antenna system. The connection between the diversity gains and ECC is given by using beneath conditions [29, 30]:

2



sii sij þ sji sjj 2   ECC ¼ pij ¼ 

2 

2  2 1  jsii j2 þ sji 1  sjj þ sij

ð2:14Þ

sij is the coupling factor between the ijth and jith elements used. p2ij is the envelop correlation coefficient. qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi DG ¼ 10
1  jECC j2 j

ð2:15Þ

In Fig. 2.12, the diversity gain of the MIMO antenna is plotted and found that it has a value around 10 dB within the resonating band. The diversity gain (DG) is being used to evaluate the MIMO antenna system’s diversity performance. The relationship between the diversity gain and ECC is provided by using Eq. (2.15). The DG of the MIMO antenna is calculated approximately by Formula (2.15), and

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Table 2.3 Comparison of proposed antenna with previously reported antennas for millimeter-wave applications Source Total size (cm) Number of ports Bandwidth (GHz) Minimum isolation (dB) Maximum gain (dBi)

[14] 3.6
2.9

[15] 11.0
5.5

[16] 4.8
2.1

[17] 0.68
0.68

[18] 1.4
2.6

This work 2
2

8

4

2

1

2

4

19–29

29.7–31.5 25

27.57–28.42, 37.62–38.37 21

26.65–29.2 36.95–39.05 22

21–30

20

27.2–29.7, 37.5–39.4 30

20

6.03

7.25–9.34

8.60

4.5

2.5

8.65

for satisfactory operation of MIMO antenna, DG should be close to 10 dBi. The value of DG of the designed MIMO antenna is 9.99 dB apart from the notched band. To feature the advantages of the proposed MIMO planar antenna, the comparison between the proposed MIMO antenna and the early announced MIMO planar antenna is done in Table 2.3. The early proposed MIMO antenna [14] has wide bandwidth, but gain of antenna is low as compared to the proposed antenna. In [15– 18], the reported antenna has wide bandwidth, but the size of antenna is too large such that antenna cannot integrate inside the circuit. Also, [16–18] reported millimeter-wave antenna has narrow bandwidth and low gain when compared to the proposed antenna. The impedance is another important parameter that defines how efficiently the device can utilize the input power. The maximum power can be transmitted when the impedance of load and source is the same. The commercially available feeding cables have 50 ohm impedance. The optimized antenna has an impedance range between 46 and 54 ohm for the operating frequency. Besides several advantages, the proposed optimized MIMO antenna has a limitation like it has a slightly lower gain than other works, but if the performance of the overall antenna is compared, then this antenna is a good candidate for future wireless millimeter-wave applications.

2.6

Conclusion

Here, a new dual-band millimeter-based patch antenna is designed for nextgeneration wireless applications. To enhance the performance of patch antenna, multi-objective PSO optimization technique is used which improves the bandwidth, gain, and efficiency of the conventional patch antenna. It is found from the results that the proposed antenna is resonating at 27.67 GHz frequency with a reflection

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45

coefficient of 35.04 dB and covers effectively the future 5G bands like 26 GHz and 28 GHz. To take the numerous advantages of MIMO antenna system like reliability of signals and high quality of service, a 2
2 MIMO patch antenna is designed by using the optimized antenna element and found that it has wide bandwidth which covers 9 GHz band from 21 GHz to 30 GHz, with maximum gain of 8.65 dB. The proposed MIMO patch antenna effectively radiates at desired frequency band and can be used for future wireless applications. Acknowledgment The authors would like to acknowledge the Visvesvaraya PhD Scheme, MeitY (India), and Science and Engineering Research Board (SERB), Department of Science and Technology (DST), Government of India, and for financial support under grant number EEQ/2019/ 000115.

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Mandeep Singh completed his BTech from the Department of Electronics and Communication Engineering, Punjabi University Patiala, Punjab (India), in 2012, and MTech from Yadavindra College of Engineering, Punjabi University Regional Campus, Bathinda (India), in 2014 in electronics and communication engineering. He is pursuing PhD in the Department of Electronics and Communication Engineering under the guidance of Dr. Simranjit Singh at Punjabi University, Patiala, Punjab, India. His work is supported by Visvesvaraya PhD scheme, MeitY, New Delhi. His research area is millimeter and sub-millimeter wave antenna design. Dr. Simranjit Singh is an assistant professor in the Department of Electronics and Communication Engineering at Punjabi University, Patiala. He is the author and co-author of about 106 research journal articles, nearly 34 conference articles, few book chapters, and book on various topics related to optical fiber communication, information security, optical sensors, and antenna design. Thus far, his publications have been cited 714 times and his H-index is 15 (Source: Scopus). His Google scholar citation is 908, i10: 26, and H-index is 17. His Research Gate citation is 698, score: 24.78, and H-index is 14. The total impact factor of his SCI journal published is greater than 70. He is recipient of more than six research grants from the Empowerment and Equity Opportunities for Excellence in Science, SERB, Government of India; ASEAN-India STI Cooperation, Department of Science and Technology (International Multilateral and Regional Cooperation Division), Government of India; Visvesvaraya PhD Scheme for Electronics and IT, funded by MeitY, Government of India (two projects); Raman fellowship funded by the University Grants Commission ( India ); and Host Scientist of C V Raman International Fellowship for African Researchers 2016 of FICCI, Government of India. Dr. Singh currently serves as associate editor of IET Electronics Letters (SCI journal, Feb. 2021 to till date) and of IET Journal of Engineering (ESCI journal, Feb. 2021 to till date). Dr. Singh received best paper award for his paper published in Optics and Laser Technology Journal. He received Host Scientist of C V Raman International Fellowship for African Researchers 2016 of FICCI, Govt. of India and was selected for Marquis Who’s Who: 2017 Albert Nelson Marquis Lifetime Achievement Award. He was nominated by the Institute of Optics at the University of Rochester for Steadman Interdisciplinary Award for Postdocs during Postdoc Appreciation Week from 19.09.2016 to 23.09.2016. He has supervised about 2 PhD theses and 19 MTech theses as well as 8 BTech. He is a life member of the Institution of Engineers (India) and the International Society for Technical Education.

Chapter 3

Fronthauling for 5G and Beyond Harpreet Kaur, Simranjit Singh, and Ranjit Kaur

3.1

Introduction

Today’s social changes are observed that an explosion of data traffic, mobile subscribers, smart devices, and rising appetite of large bandwidth are skyrocketing and sow the seed for the necessity of new generation. Cellular networks have made revolutionary developments in telecom industries and introduced superfast network fifth generation (5G) and vision of beyond 5G. The new-generation 5G presents legacy system that has 1000x times more strength than the previous generation [1]. The transmission demand, large bandwidth, little jitter, ultra-speed, and efficient resource allocation are the major challenge for both networks 5G and 6G. China has launched the proposal for 6G vision, in which more multimedia connectivity, increased options for the gaming, high frequency band, reliable network technology/topology, large wavelength, etc. will be the basic demands and 6G will be 1000x times faster than 5G too [2]. As the rapidly explosion of network collision, the infrastructure needs to expand the essentiality of the highly qualitative, with ultraperformance, maintained and updated network. But it’s extremely to provide this much of strong network because of some causes that are hard to operate, update, and maintain the entire network structure for the operators. Here, we have some reasons like high amount of data traffic, inefficiency of operators, complex transmitter network, lack of knowledge, and expenses. Therefore, the 5G transport network is divided into small segments that present the backhaul, midhaul, and FH [3]. Backhaul serves the connection from core network to central office that consists of multiple baseband units under the pool and called as OLT, while midhaul serves

H. Kaur (*) Department of Computer Science, Punjabi University, Patiala, Punjab, India S. Singh · R. Kaur Department of ECE, Punjabi University, Patiala, Punjab, India e-mail: [email protected]; [email protected] © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 S. Singh et al. (eds.), Broadband Connectivity in 5G and Beyond, https://doi.org/10.1007/978-3-031-06866-9_3

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the linking between FH and FH aggregations. The FH network provides the connectivity among the OLT under the central office to ONUs under the remote radio head [4]. These network chunks are easy to operate and update. To match the 5G and beyond transport network demands and to facilitate the applications at the desired speed, various PON technologies are available with multiplexing techniques and hybrid techniques like NGPON. The wavelengthdivision multiplexing (WDM) and time-division multiplexing (TDM) are the candidate techniques for the NGPON that help to save the power, multiple gigabits, or terabits data rate by using multiple wavelengths, large bandwidth flexibility, and ultra-frequency band using millimeter-wave spectrum band [5]. In view of the future, as the network collision, digital smart devices, gadgets, and cell phone subscribers are increasing, the bidirectional multicore fiber is another option that can provide the bit rate in tera, peta, etc. with the widest bandwidth. The drawbacks of this fiber like cross talk, nonlinearity effect, dispersion, and noise are other aspects that are considerable too [6]. Some existing advance transmission techniques and technologies like quadrature amplitude or differential phase-shifting or phase amplitude modulation techniques using NGPON or others can be used to deal with the abovementioned drawbacks [7]. Although 5G is already launched in some countries like South Korea, the United States and China, the rest of the countries are ready to launch, whereas 6G is at its early phase. In this proposed chapter, the symmetric simulation on millimeter wave over dense-wave division multiplex-PON (MMWoDWDM-PON) transceiver for FH network is presented with positive outcomes. The results have been analyzed in terms of quality factor and bit error rate along with the eye diagram.

3.1.1

High-Capacity (Tbps) Optical Transmission

Optical transmission is the guided media where the input signal is transmitted on the fiber link in the form of light that provides the robust and reliable transmission rather than other existing mediums. Optical fiber is the most prominent solution for the large bandwidth and long coverage area. In other words, we can say that it can be a long-term investment in the telecommunication industry for the ubiquitous connectivity of the world [8]. From source to destination, the coverage distance of thousands of miles in the communication world is the work of minutes that shows the fiber potentials. It can provide ultra-speedy network with bit rate at the hundreds of terabits per second, frequency spectrum in hundreds of terahertz, and ultra-low jitter [9]. For the 5G and beyond, it is best to connect the tangible realm to the intangible world.

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PON Standards

PON is a network approach that is basically utilizing optical fiber which is used to serve the telecommunication networks for reliable transmission process. The telecommunication network organizations have made signal modulation on optical link possible. It provides the interface from OLT to ONUs or optical network terminals (ONT) by using the unpowered splitters called ODU under the domain of optical. The terms ONUs and ONTs are interchangeable that carries the same meaning but under the different telecommunication standards, IEEE and ITU-T, respectively [10]. It serves a large number of users by utilizing the point-to-multipoint topology via both upstream and downstream transmission directions shown in Fig. 3.1. In these days, network is suffering with the explosion of collision at the user end. As it’s been seen, growth end users, smart devices, network traffic, and telecommunication network need to attain the large bandwidth, ultra-bit rate, and small jitter. Some researches have been conducted to predict the future. The mobile statistical report has predicted that the mobile users will be increased by 7.2 billion within the 2022 [11], whereas the report of Cisco Annual Internet 2018–2023 has given the figure around 29 billion that the growth of smart devices will see a huge jump [12]. The exponential high lump in end users and smart devices is caused by the network traffic. Within the 2022, network collision will touch the number around 77 exabytes [13]. Figure 3.2 shows that China and India are on peak level of mobile user’s growth. PON is a highly efficient technology that can perform the multiplexing techniques on finite fiber resources to serve the enormous mobile subscribers by providing the huge bandwidth at the high bit rate with ultralow latency. For better performance, PON is classified into two categories that are asynchronous and synchronous developed under the standardized ITU-T and IEEE. Under these categories, some classes are available like broadband-PON (BPON) and Ethernet-PON (EPON); both come under asynchronous transfer mode PON (ATM-PON), whereas gigabit PON

Fig. 3.1 Basic passive optical network structure

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(GPON) comes under synchronous transfer mode PON (STM-PON) [15]. Abovementioned modes were capable as per their specifications in specific era. Except APON and BPON, EPON and GPON were selected because of their features by ITU and IEEE and extended them for the FH network’s requirements. The PON standards are categorized into various ways that are EPON, GPON, NGPON1, NGPON2, etc. and present their own way for the 5G FH network.

EPON In 2004, the IEEE was working under the 802.3 ah and developed the EPON that was capable to carry the transmitted signal data in the encapsulated format during the Ethernet communication. It was presented as the less expensive network architecture that was compatible for the huge mobile users with the enhanced bandwidth and network performance [16]. During the network communication, it supported two separate multiplexing techniques that are TDM-PON and WDM-PON [17]. These techniques can handle the network traffic at the user end and provide the sufficient bandwidth during interface by utilizing the optical resources. OLT unit can utilize more than one wavelength for downlink, whereas ONU unit works on time slots that are assigned to the different ONUs during uplink. Due to the fine features of EPON, it was the technology that could replace the APON and BPON [17]. Despite being a replacement technology, it was incapable to the next generations for the collision.

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GPON The FSAN has taken the initiation and started the process of development of GPON in 2001. After some progress, under the series G.984 standard ITU-T, it was selected in 2003 as a PON family. Many researchers and vendors who could provide the platform have contributed and played a huge role to make the collaboration with the mobile network generations possible [15]. There’s no doubt that it presents the complex and costly infrastructure than the EPON to serve the huge bandwidth for the high transmission rate for the flexible cellular communication. It can serve in both manners whether it is symmetric and asymmetric network system. It can support the input signal at 1.25 Gbps/1.25 Gbps and 2.5 Gbps/1.25 Gbps of transmission rate for symmetric and asymmetric, respectively. It used TDM-PON technique and covered the distance of 40 km by using one wavelength [18]. As the mobile network subscribers are growing day by day, the technology was needed still for the hunger of high bit rate and high spectrum band for huge bandwidth.

XGPON (NGPON1) After this struggle, the telecommunication standards have started the work on the multiple gigabits to increase the transmission rate as per the growing demand. This is an emerging technology and has been launched as a descendent of the GPON under the standard ITU-T series G.987 [18]. As a next-generation PON technology, it is capable to provide transmission at the 10 Gbps bit rate so, also known as a 10G-PON or NGPON phase 1 (NGPON1). The symbol “X” is used as a Roman to represent the numerical number 10, and XG-PON is another name given to this technology. For the asymmetric and symmetric interface mode, the terminologies XG-PON and XGS-PON have been used respectively where 10 Gbps/2.5 Gbps is presented as an asymmetric downlink and uplink and 10 Gbps/10 Gbps is presented for symmetric bidirectionality [19]. The XGS-PON is recognized as a ITU-T G.9807.1 standard in 2016 while accepted in 2017 by taking the extension of NGPON1 [8]. It provides multiple gigabits and huge bandwidth but could not satisfy the 5G FH cellular network demands as per the specifications. The high-speed data rate, more wavelengths, large amount of bandwidth, high spectrum band, and low jitter are still the matter of concern to serve the large number of ONUs at the remote head. So, the flexible network technology is needed and NGPON2 has developed.

NGPON2 As an offspring of GPON and NGPON1, NGPON2 has launched and presented the new way of thinking by the hybridization of multiplexing techniques to meet and facilitate the FH network. The multiplexing techniques are WDM-PON and TDM-PON and got together to become a TWDM-PON. In 2012, the FSAN has

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taken the initial pace to start the research in order to increase the data rate by multiplexing the multiple wavelengths at the 10 Gbps of bit rate per wavelength [18]. In 2013, NGPON2 has gotten the recognition by ITU-T G.989 and become the technology that can support 40 Gbps in aggregation or more that it is in both formats called symmetric and asymmetric [20]. As per the requirements and specifications of FH network infrastructure, the 40 km of distance can be covered by the fiber link. TWDM-PON network infrastructure inherited the features of GPON and NGPON1 by the coexisted structure of C-RAN under the CPRI protocol. TWDM-PON is selected as a sufficient solution for the NGPON2 to match the 5G FH. In the asymmetric approach, the downlink and uplink utilize the 10 Gbps/2.5 Gbps of bit rate, respectively, while 10 Gbps/10 Gbps is used during both directions in symmetric mode. It is the best technology that can use four and more wavelengths for the fiber to the x that describes the home, building, curb, etc. with the tremendous outcomes like quality of services and experiences [21]. It provides the mature network two times large bandwidth, four or more wavelength plan, low energy consumption, high bit rate, less expensive network structure, and flexibility with high efficiency that makes it consistent. Although it offers these key features, it also introduces future scope to be investigated – two major concerns that present the enhancement in data rate at single wavelength along with the multiplexing of two wavelengths. Therefore, the high-speed PON is needed to deal with these obstacles.

Concept of 50G-PON 50G-PON is also known as a HS-PON or NGPON2+ because it offers 25 Gbps or 50 Gbps of rate at a single wavelength that can enhance the FH network performance. Under ITU-T G.9804 and IEEE 802.3ca, it has presented three types of techniques that are TDM-PON at 50/25 Gbps, TWDM-PON at 50/25 Gbps, and higher-speed point-to-point WD-PON at 50/25 Gbps [22]. This concept can increase the bandwidth five time times faster. ITU-T supports the 50 Gbps at per channel, while 25 Gbps belongs to the IEEE at per channel and makes an aggregation using two wavelengths to meet the NGPON2+ for both symmetric and asymmetric modes [23]. It introduces benefits that are to reduce the network setup cost, space, and energy consumption too. It prefers the coexisting infrastructure and wavelength plan with GPON, NGPON1, and NGPON2. Eventually, PON technologies can accommodate the 6G FH network as well as 5G cellular network with the ultra-speed and ultra-efficiency. This revolutionary path will open the way to meet the 6G FH mobile network requirements. The 5G network architecture will be a foundation of the architecture of beyond network 6G.

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Millimeter Wave over Fiber

Millimeter wave is a high-frequency radio spectrum wave signal that provides a range between 3 GHz and 300 GHz. It contains innumerable frequency spectrums that are already being used in some communication systems. Despite the availability of E-band, W-band, V-band, etc., the millimeter-wave spectrum is unutilized [24]. In 2013, South Korea and the United States conducted field research and have shown indoor and outdoor tests and presented their coverage range for this spectrum band under LOS and NLOS scenarios. The coverage era of 1.7 km was for LOS and 200 m was for NLOS [25]. Basically, the millimeter-wave spectrum band is classified into two categories that are super high-frequency (SHF) spectrum band that provides range between 3 GHz and 30 GHz and extremely high-frequency (EHF) spectrum band that provides range between 30 GHz and 300 GHz. The length of the wave lies between 1 mm and 10 mm; that’s why it is called millimeter wave [24]. It is an exponentially strengthened spectrum band that is used in wireless communication network. But there are some specific problems that have been encountered during wireless transmission process like path loss due to wall or tree or building, data loss due to rain or bad weather or weak signal, and non-line of sight for both. In the last decades, an immense growth is seen in cellular subscribers, modern devices, and data collision that gave birth to troubles and demands of high-speed network with large bandwidth and low latency that showed another aspect [26].The millimeter wave is a rich source of these demands with small wavelength. The spectrum band millimeter wave is shown in Fig. 3.3. The MMWoF is a way to deal with these scenarios after considering all issues and last decade’s necessities. The MMWoF is the key technique that provides converged schematic approach of millimeter wave and optical fiber. In this process, the millimeter wave is generated by using existing modulation techniques and transmitted on the optical fiber link bidirectionally from OLT to ONUs and vice versa [27]. It’s a very significant process that provides the high-speed fronthaul network with huge bandwidth, low power consumption, interaction with immunity of signal from interference, fusion capacity, and less expense [28]. The way of MMWoF approach is led by the RoF.

Fig. 3.3 Millimeter-wave spectrum band

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Radio over Fiber

The radio over fiber (RoF) is the fundamental concept behind the MMWoF techniques. RoF is the technology that offers hybrid technology that congregates the radio-frequency signals and fiber connection. In this process, the radio signals are generated which are modulated in the form of light, and fiber connection is used as guided medium to make the signal travel [4]. As per the fronthaul requirements for 5G and beyond, the RoF grounded radio access network has introduced the centralized network to accommodate more users and to provide enhanced broadband network with low latency and Internet of Things [29]. Centralized radio network serves the connection between baseband unit and remote radio unit by the use of digitized distributed unit. The baseband units are centralized providing collection of baseband units called central office and are directly connected with the remote head via fiber link under the domain centralized radio access network [30]. To meet the bandwidth demand, radio network transmission process is shown in Fig. 3.4. The figure shows the concept of RoF where centralized unit is fully responsible to operate the distributed unit as well as remote unit except their basic operations. The distributed unit is responsible for the digital processing during the transmission process, whereas remote unit is answerable to amplify the transmitted signal and its conversion. The implementation of fronthaul network is done by using the Common Public Radio Interface (CPRI) or Open Base Station Architecture Initiative (OBSAI)[29]. Although the RoF-based fronthaul network is capable to reduce the overall network deployment expenses, somewhere, it is inapplicable for serving the enormous data traffic, bandwidth starvation, and technically deployment expenses. To sort out the abovementioned obstacles, the congested radio-frequency band is not a sufficient solution for the high transmission rate, large bandwidth, accommodation of enormous mobile users, and low jitter. So, the high spectrum band with extremely high-range millimeter wave is needed to beat the fronthaul bandwidth and the rest of the demands.

Fig. 3.4 Block diagram of RoF

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Long-Reach PON

Long-reach PON presents a span of hundred kilometers and beyond. As per the 5G broadband network requirements, protection and security are the major aspects that PON is concerned with. In the 5G network infrastructure, the FH network can cover 20–40 km of area via fiber using the different advance technologies under the specifications of separate standards such IEEE and ITU-T discussed in the section PON standards. The PON need to extend hundreds of kilometers of the coverage area, and it is called long-reach PON. There are various advance PON technologies available that can help to attain this milestone. With the large coverage distance, PON can reduce the network’s operational and capital expenditures and can accommodate the broadband users in large figure [31]. There are some challenges that are making the concept attractive. The source of optical power consumption by the signal, resource allocation process during the uplink transmission, network topology, and security are one of them [32]. Many existing advance technologies are capable to serve the long reach under the new series of IEEE and ITU. The multiplexing techniques like TDM, DWDM, OFDM, OCDM, etc. are potential techniques to serve the large coverage span and mobile population. It can be beneficial for the metro and large number of ONUs and can reduce the setup cost.

3.1.6

Advanced Modulation and Multiplexing Techniques

Modulation techniques are available to generate the millimeter-wave signal and transmit over fiber. PON provides various modulation techniques that use laser diode as an optical source to convert the electrical signal into a high spectrum light signal. After the conversion process, the signal is modulated on fiber link, and photodetector detects the optical signal and converts it into electrical again to deliver the users. Each modulation technique has its own procedure to generate the millimeter-wave signal as per their own specifications and that are the following:

Direct Modulation Direct modulation is a simple way to generate a millimeter wave, and it is reliable for covering short distance at the low frequency spectrum. In this approach, the direct modulated laser is multiplied with the radio-frequency signal to generate the millimeter wave that is modulated over the fiber and detected by the PIN photodetector to convert and recover the signal in electrical form [33]. The direct feedback laser is used to increase the data transmission rate. Except the direct feedback laser, some other lasers like semiconductor laser is presented a separate path to increase the bandwidth [34]. It has another name called intensity modulation technique that does

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not support any external modulator device to generate a millimeter wave. So, it is a less expensive approach. But due to the small coverage distance along with the low frequency spectrum, the external modulation technique is presented in the next subsection.

External Modulation External modulation technique provides an enhanced schematic approach in terms of large coverage distance at the high spectrum frequency and presents carrier suppression that supports high-velocity generation [33]. It offers enhanced broadband network performance and large bandwidth to accommodate the large number of end users. Under the intensity and phase modulation schemes, it provides different modulators, i.e., amplitude modulator, quadrature amplitude modulator, and phaseshifting key modulator, respectively. An intensity modulator uses the direct modulated laser as a source and external modulator like Mach-Zehnder modulator (MZM) known as an external intensity modulation, whereas phase modulation presents phase-shifting feature for the transmitted signal using MZM. Under the phase modulation technique, to pass the constant current, the continuous wave laser is used that helps to reduce the chirp [35]. It is more convenient than the direct modulation technique due to its features but suffered because of its expensive structure.

Up and Down Conversion Up- and down-conversion modulation technique is a flexible approach that facilitates the radio signal with conversion system which can be into high form or low form. The approach is known as up conversion when the radio spectrum signal is changed into high spectrum frequency band, whereas when the signal is changed into low spectrum band it is called down-conversion modulation system [36]. The concept of the up-conversion modulation is different from the down-conversion system because intermediate frequency signals are used in the up-conversion scheme [37]. The intermediate frequency signal is reliable and free from dispersion.

Heterodyne Modulation Heterodyne modulation technique provides the high spectrum frequency band generation scheme that uses more than one optical input signals by using tunable lasers to enhance the purity of signal [38, 39]. It helps to deal with the chromatic dispersion. The optical coupler is used to combine or mix the two tunable lasers to modulate the new spectrum band at the separate frequencies. It also contains problem of phase noise [39].

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All modulation techniques have their pros and cons that make it separate from each other. With the help of these, the extremely high spectrum band millimeter wave can be generated that can provide the huge bandwidth to the 5G FH network and beyond. To serve the 5G FH broadband network, PON multiplexing techniques use the abovementioned approaches to modulate the millimeter wave signal and transmit it on the fiber to sort out the problem of transmission loss.

Multiplexing Techniques There are many existing multiplexing techniques that can be capable to serve the FH networks like time-division multiplexing, frequency division multiplexing, and wavelength division multiplexing. PON-based network infrastructure provides the reutilization of limited fiber resources and uses the preemption during transmission process to make the mobile users satisfy in terms of speed. To use finite resources like bandwidth in an effective way, there is a need for multiple wavelengths to serve the user demands, and the dense wavelength division multiplexing technique is the key solution [40]. WDM technique is based on passive optical network (PON) used to improve the bandwidth more greatly by multiplexing the number of optical signals using carrier channels at the different spectrum range. The WDM-PON is used to multiplex the limited channels that transmit on a single fiber. But to serve the large subscribers, we need the multiplexing technique to multiplex the huge input channels that are called DWDM. DWDM is a rich technique with constricted channel space to accommodate the more than eight-channel wavelengths [41, 42]. The erbium-doped fiber amplifier (EDFA) is an amplifier that is used to amplify the signal in prepone manner and to boost up the energy level of the signal which is beneficial especially to increase the channel bandwidth [43]. The WDM also goes under the two major issues, chromatic dispersion due to the use of the same fiber and the nonlinear effect of four-wave mixing. Despite these issues, the DWDM is the way to utilize the bandwidth systematically, and the convergence of DWDM-PON and MMWave over fiber is best for the fronthaul network [42]. The fundamental focus of the proposed network technique is to extend the single-channel capacity to serve that attracts the fronthaul property. To comprehend the notion of millimeter-wave modulation over optical link, the MMWave over DWDM system is designed for the 5G fronthaul network. It can make the complete use of unused frequency bands through the same fiber. The simulation setup and experimental results have been discussed below. Our system’s reliability and operability are successfully investigated via practical outcomes of a broadly open eye diagram with near to ground error rate.

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System Setup The proposed simulation aims to design the symmetric 5x16 Gbps DWDM-PONbased 5G fronthaul system by using extremely high spectrum frequency band MMWave that is transmitted on single-mode fiber to fast the network. In the approach of MMWave over the DWDM system, the 16-DWDM scheme is the most prominent technique to utilize the bandwidth to deal with the augmentation of mobile subscribers and to save the power and cost of the structure. The typical bidirectional 5x16 Gbps MMWave over DWDM-based infrastructure for the fronthaul network is shown in block diagram in Fig. 3.5 for the 5G fronthaul mobile network communication system. The simulation setup is shown in Fig. 3.6 that consists of 16 transceivers in the optical network terminal (OLT) unit and the optical network unit (ONU), which are connected via the same fiber at the 20-km distance. In the infrastructure of 16-DWDM Fig. 3.2, the components go through the OLT that are PRBS generator to generate the random bits, non-return to zero (NRZ) for pulse generation, sine wave at 100 GHz, electrical multiplier to merge the NRZ and sine wave, continues wave (CW) laser at 193.1 THz with the power of 10 dBm, external modulation technique called single-drive mach-zhender modulator with erbium-doped fiber amplifier (EDFA), is used to modulate the signal in light during transmission. In this, 16 channels are multiplexed and transmitted on the same fiber with the help of EDFA amplifier which enhances the signal and covers the 5-m distance. The optical spectrum analyzer (OSA) helps to examine the wavelength spectrum. Transmitter uses the 5 Gbps transmission rate per channel. Table 3.1 shows the required parameters for the simulation system.

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Fig. 3.5 Schematic bidirectional approach MMWave over 16-DWDM

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Fig. 3.6 Basic schematic transceiver

Table 3.1 Key parameters for simulation setup

Parameters Transmitter DWDM MZM Bit rate Frequency Power EDFA OSA Single-mode optical fiber Receiver DWDM PIN LPBF 3R regenerator

Description 16 number of input ports Dual MZM 5 Gbps 193.1 THz 10 dBm 5m Analyzer 20 km 16 number of input ports Photodetector Cutoff frequency 0.75

After transmission, fiber provides the output to the optical demultiplexer to split as per the requirement. The demultiplexer serves the output to the 16 receivers which comes under the ONU on the receiving side. It separates the channels via a specific ONU. The receiver contains components which are photodetector that detects the optical signal from demultiplexer and converts it into electronic form, a low-pass Bessel filter (LPBF) to filter the received electronic signal, a 3R regenerator to recover the data, and an analyzer to evaluate the error rate. The 3R regenerator is a component to recover the data by performing the three functions such as reshaping, retiming, and re-amplification. In simple words, one can say that it works as an NRZ pulse generator. The specific error tester tool is used that is called BER spectrum analyzer to get to know about the threshold value, error measurement, Q-factor, and discount factor too with the eye diagram.

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Results and Discussion In this study, the MMWave over DWDM system is investigated for the different high MMWave spectrum bands without any compensation of dispersion using the optiwave-18 simulation software. The performance of the proposed system demonstrated the successful outcomes via vital parameters such as power, Q-factor, BER, and wavelength spectrum. The different optical spectrum analyzers from the separate simulation setups are shown in Fig. 3.7 that is used to present the input channel wavelength before transmission and after transmission. The first diagram presents

Fig. 3.7 At the different spectrum bands, 50 GHz, 80 GHz, and 100 GHz: (a) optical spectrum before the transmission and (b) optical spectrum after the transmission

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Table 3.2 Downstream and upstream Q-factor and BER for different channels for NRZ modulation format Wavelengths (nm) Q-factor Downstream transmission: at 50 GHz MMWave spectrum band Ch1 ¼ 1552.52 6.9 Ch8 ¼ 1548.51 7.8 Ch16¼ 1541.34 7.8 At 80 GHz MMWave spectrum band Ch1¼ 1552.52 6.8 Ch8¼ 1548.51 6.6 Ch16¼ 1541.34 6.4 At 100 GHz MMWave spectrum band Ch1¼ 1552.52 6.9 Ch8¼ 1548.51 6.7 Ch16¼ 1541.34 7.3 Upstream transmission: at 50 GHz MMWave spectrum band Ch1¼ 1552.52 7.3 Ch8¼ 1548.51 7.5 Ch16¼ 1541.34 7.5 At 80 GHz MMWave spectrum band Ch1¼ 1552.52 7 Ch8¼ 1548.51 7.7 Ch16¼ 1541.34 7.4 At 100 GHz MMWave spectrum band Ch1¼ 1552.52 7.1 Ch8¼ 1548.51 7.6 Ch16¼ 1541.34 7.3

BER 5.83  1011 9.34  1013 3.03  1013 9.46  1011 5.91  1013 9.05  1011 9.46  1011 9.80  1012 8.80  1012 1.45  1011 2.36  1014 1.56  1013 1.04  1011 3.83  1014 4.25  1013 4.87  1013 3.08  1014 1.55  1013

the analysis of the optical signal before the transmission, while the other one depicts the spectrum after transmission. The transmission channels vary and are distinguished by the quality and error rate at the given distance, and some of them are displayed in Table 3.2. It would be appropriate to say that upstream, downstream, and increasing MMWave spectrum always directly influence the Q-factor as well as error rate. With the perspective of better understanding, the system is investigated with the help of an eye diagram of the transmitted signal at different error rates. The widely opened eye shows the efficiency of the signal with the Q-factor. According to the observation of eye diagrams, the presented scheme verified our idea of enrichment in MMWave over the DWDM system by using the MMWave spectrum band with the same fiber. The 16-DWDM system is used to fight against hunger for large bandwidth at a high-speed transmission rate to utilize the bandwidth in a well-organized way. In the proposed system, Figs. 3.8 and 3.9 portray the best case of downstream and upstream eye patterns of all three simulations by using single transmission channel 8 for the NRZ modulation format.

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Fig. 3.8 Eye diagrams for different downstream simulation setups: (a) at 50 GHz, (b) at 80 GHz, (c) at 100 GHz

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Fig. 3.9 Eye diagrams for different upstream simulation setups: (a) at 50 GHz, (b) at 80 GHz, (c) at 100 GHz

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In Fig. 3.10, we also present the altogether simulation’s proportion of study at Q-factor for both upstream and downstream differences at separate increasing spectrum bands. The curved blue line expresses the upstream variations, whereas the red curved line displays the downstream transmission in Fig. 3.10a–c. Each channel has its distinct Q-factor. To analyze all ups and downs during upstream and downstream signal transmission, Figs. 3.11 and 3.12 present all users at OLT and ONU units. It also can be increased as per the requirement of 5G fronthaul network subscribers. The blue line shows the MMWave spectrum band at 50 GHz, red line at 80 GHz, and blue line at 100 GHz corresponding to the Q-factor variations for downstream and upstream. The convergence of 16-DWDM and MMWave over fiber system for the fronthaul network at the 100 GHz represents the smooth and better flow of changes than other lines, suffering from the large ups and downs during transmission. From the figures, it’s cleared that the downstream Q-factor graph is differed from upstream. Figure 3.13 presents the system performance concerning the error rate ups and downs for all simulations at the rising spectrum band associated with the DWDM fronthaul network. The BER remains less than 1016 that shows acceptance.

3.1.7

Multicore Fiber

Multicore fiber provides the multiple cores in the same cladding of fiber that helps to speed up the transmission as well as bit rate. It facilitates the parallel system for data transmission at the rate of Pbit/s or Ebit/s concurrently [6]. It promotes the technique space division multiplexing, and till now transmission has been done using 32-core fiber. It is very helpful to increase the multiple special channels to enhance the 5G FH transport performance. Despite all these features, it suffers from some aspects like noise, dispersion, nonlinearities, cross talk, etc. that lower the network performance at the long distance like thousands of km. But the advance transmission techniques can help to reduce these obstacles and enhance the network performance. 5G FH mobile network serves the small distance as mentioned in above sections. Therefore, it is already cleared that to extend the fiber distance and improve the bit rate, bandwidth, lower response time, and finite optical resource utilization, special multiplexing using multicore fiber is the best technique for 5G as well as beyond network as per the requirements and vision of 6G. The multicore fiber can meet the requirements of 6G FH network to provide the applications of the same as hologram, digital cloning, etc. for the ubiquitous connectivity all over the world.

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a 7.8

At 50 GHz (US) At 50 GHz (DS)

Q-Factor

7.6 7.4 7.2 7.0 6.8 CH 1 CH 2 CH 3 CH 4 CH 5 CH 6 CH 7 CH 8

Input Channels

b

At 80 GHz (US) At 80 GHz (DS)

7.8 7.6 7.4 Q-Factor

Fig. 3.10 Q-factor variations during upstream and downstream transmission for all simulation setups: (a) at 50 GHz, (b) at 80 GHz, (c) at 100 GHz

7.2 7.0 6.8 6.6 CH 1 CH 2 CH 3 CH 4 CH 5 CH 6 CH 7 CH 8

c

Input Channels 8.0 At 100 GHz (US) At 100 GHz (DS)

7.8 7.6 Q-Factor

3

7.4 7.2 7.0 6.8 CH 1 CH 2 CH 3 CH 4 CH 5 CH 6 CH 7 CH 8

Input Channels

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Fig. 3.11 The comparison of Q-factors versus different wavelengths for downstream transmission at the different spectrum bands

Fig. 3.12 The comparison of Q-factors versus different wavelengths for upstream transmission at the different spectrum bands

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Fig. 3.13 Bit error rate corresponding input channels

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Bidirectional Optical Communication for 5G and Beyond

All PON-based technologies present the bidirectional network infrastructure for both symmetric and asymmetric modes. However, it’s true that all technologies follow their own specification whether it comes under the network’s requirement and specifications of ITU or IEEE standard series. As abovementioned, symmetric simulation setup presented the bidirectional system by utilizing the bidirectional fiber and positive results at different frequency spectrums. Uplink and downlink transmission is done simultaneously using single-mode fiber that provides the same core for both directions. For the uplink and down ink, there are two left and right sidebands that are used to transmit the input signal by the allocation method. Using the bidirectional fiber link, there will be some problems during the transmission communication that are interference, fiber dispersion, and noise, impacting the transmission signal directly [7]. Abovementioned obstacles can be easily reduced by using the advance signal modulation techniques. The Quadrature amplitude modulation or phase-shifting key modulation is the solution to these problems, which can easily reduce the inter-core cross talk, noise, fiber dispersion, etc. for the 5G FH and beyond, as well as bidirectional optical link which can perform better results.

3.1.9

Conclusion

This chapter presents the concept of FH network for 5G and beyond and the essentiality of the distinction of PON technologies and techniques. Utilization of extremely high-spectrum band millimeter wave is one of the better options to extend the bandwidth to satisfy the starvation of speedy network. This chapter presents the simulation of MMWoDWDM-PON and better results by using the bidirectional fiber via left and right band during the symmetric transmission. As per the vision of 6G network, required data rate and bandwidth should be in tera, so multicore fiber can help to achieve the visional milestones of transport network. To reduce the fiber dispersion, nonlinearity effect, and noise, some advanced techniques can be beneficial.

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25. W. Roh et al., Millimeter-wave beamforming as an enabling technology for 5G cellular. IEEE Commun. Mag. 52(2), 106–113 (2014) 26. G. Kalfas et al., Next generation fiber-wireless fronthaul for 5G mm wave networks. IEEE Commun. Mag. 57(3), 138–144 (2019). https://doi.org/10.1109/MCOM.2019.1800266 27. P. T. Dat, A. Kanno, K. Inagaki, N. Yamamoto, and T. Kawanishi, “High-spectral efficiency millimeter wave-over-fiber system for future mobile fronthaul,” Eur. Conf. Opt. Commun. ECOC, 2015, 1, pp. 1–3, 2015, doi: https://doi.org/10.1109/ECOC.2015.7341822. 28. C.T. Tsai, C.H. Lin, C.T. Lin, Y.C. Chi, G.R. Lin, 60-GHz millimeter-wave over fiber with directly modulated dual-mode laser diode. Sci. Rep. 6(1), 1–12 (2016). https://doi.org/10.1038/ srep27919 29. M. Sung, S.H. Cho, J. Kim, J.K. Lee, J.H. Lee, H.S. Chung, Demonstration of IFoF-based mobile fronthaul in 5G prototype with 28-GHz millimeter wave. J. Lightwave Technol. 36(2), 601–609 (2018). https://doi.org/10.1109/JLT.2017.2763156 30. T.R. Raddo, S. Rommel, B. Cimoli, I.T. Monroy, The optical fiber and mmwave wireless convergence for 5G fronthaul networks, in IEEE 5G World Forum, 5GWF 2019 – Conference Proceedings, no. 2019 (2019), pp 607–612. https://doi.org/10.1109/5GWF.2019.8911613 31. Z. Li et al., Symmetric 40-Gb / s , 100-km Passive Reach with 53-dB Loss Budget. J. Lightwave Technol. 32(21), 3389–3396 (2014) 32. H. Song, B. Kim, B. Mukherjee, Long-reach optical access networks: a survey of bandwidth assignment mechanisms. Communications 12(1), 112–123 (2010) 33. J. Xiao et al., Review on the millimeter-wave generation techniques based on photon assisted for the RoF network system. Adv. Condens. Matter Phys. 2020 (2020). https://doi.org/10.1155/ 2020/6692941 34. A.L. Balan, N.D. Alexandru, Inter-symbol interference free pulses for transmission over intensity-modulated channels. IEEE Int. Conf. Commun., 4–7 (2014). https://doi.org/10.1109/ ICComm.2014.6866679 35. G.H. Nguyen, Y. Le Guennec, Generation of 60-GHz MB-OFDM signal-over-fiber by up-conversion using cascaded. Lightwave 27(11), 1496–1502 (2009) 36. Up-Down Converter and Mixers _ Authorized Distributor _ Arrow. 37. K.I. Kitayama, R.A. Griffin, Optical downconversion from millimeter-wave to IF-band over 50-km-long optical fiber link using an electroabsorption modulator. IEEE Photon. Technol. Lett. 11(2), 287–289 (1999). https://doi.org/10.1109/68.740732 38. X. Feng, P. Yang, L. He, F. Niu, B. Zhong, H. Xu, Heterodyne system for measuring frequency response of photodetectors in ultrasonic applications. IEEE Photon. Technol. Lett. 28(12), 1360–1362 (2016). https://doi.org/10.1109/LPT.2016.2542839 39. D. Singh, P. Singh, Techniques of millimeter-wave signal generation in ROF systems: a review. Int. J. Comput. Appl. Inf. Technol. I, Issue II I(II), 2278–7720 (2012) [Online]. Available: www.ijcait.com 40. A. Kumar, A. Sharma, A 5x16 Gbps DWDM system for ground-to-satellite using RZ signaling scheme under different turbulences. Proc. Comput. Sci. 115, 115–122 (2017). https://doi.org/ 10.1016/j.procs.2017.09.084 41. S. Singh, Bandwidth efficient hybrid modulation technique in the scenario of 3.5 Tb/S dense wavelength division multiplexed system. Optoelectron. Adv. Mater. Rapid Commun. 11(1–2), 51–53 (2017) 42. S. Parkash, A. Sharma, H. Singh, H.P. Singh, Performance investigation of 40 GB/s DWDM over free space optical communication system using RZ modulation format. Adv. Opt. Technol. 2016 (2016). https://doi.org/10.1155/2016/4217302

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Harpreet Kaur received her BCA degree in computer applications from Punjab University, Chandigarh, India, in 2012 and MCA degree from Sri Guru Granth Sahib World University, Fatehgarh Sahib, Punjab, India, in 2016. Currently, she is perusing PhD at Punjabi University, Patiala, Punjab, India, under the computer science stream. Her research area includes fiber-optic communication and machine learning for the 5G fronthaul networks. Dr. Simranjit Singh is an assistant professor in the Department of Electronics and Communication Engineering at Punjabi University, Patiala. He is the author and co-author of about 106 research journal articles, nearly 34 conference articles, few book chapters, and book on various topics related to optical fiber communication, information security, optical sensors, and antenna design. Thus far, his publications have been cited 714 times and his H-index is 15 (Source: Scopus). His Google scholar citation is 908, i10: 26, and H-index is 17. His Research Gate citation is 698, score: 24.78, and H-index is 14. The total impact factor of his SCI journal published is greater than 70. He is recipient of more than six research grants from the Empowerment and Equity Opportunities for Excellence in Science, SERB, Government of India; ASEAN-India STI Cooperation, Department of Science and Technology (International Multilateral and Regional Cooperation Division), Government of India; Visvesvaraya PhD Scheme for Electronics and IT, funded by MeitY, Government of India (two projects); Raman fellowship funded by the University Grants Commission (India); and Host Scientist of C V Raman International Fellowship for African Researchers 2016 of FICCI, Government of India. Dr. Singh currently serves as associate editor of IET Electronics Letters (SCI journal, Feb. 2021 to till date) and of IET Journal of Engineering (ESCI journal, Feb. 2021 to till date). Dr. Singh received best paper award for his paper published in Optics and Laser Technology Journal. He received Host Scientist of C V Raman International Fellowship for African Researchers 2016 of FICCI, Govt. of India and was selected for Marquis Who’s Who: 2017 Albert Nelson Marquis Lifetime Achievement Award. He was nominated by the Institute of Optics at the University of Rochester for Steadman Interdisciplinary Award for Postdocs during Postdoc Appreciation Week from 19. 09. 2016 to 23. 09. 2016. He has supervised about 2 PhD theses and 19 MTech theses as well as 8 BTech. He is a life member of the Institution of Engineers (India) and the International Society for Technical Education. Ranjit Kaur is working as a professor in the ECE Department at Punjabi University Patiala. She is serving as a head of the department and is the author and co-author of about the 69 research publications, 47 international journals, and 22 national journals. She has guided 28 theses. She is a lifetime member of the Indian Society for Technical Education (ISTE) and member of IEEE and International Association of Engineers (IAENG). She is also a reviewer for reputed international journals, viz. IEEE Transactions on Circuits and Systems II: Express Letter, IEEE Signal Processing Letters, International Journal of Electrical Power and Energy Systems (Elsevier), Journal of King Saud University – Computer and Information Sciences (Elsevier), WSEAS Transactions on Signal Processing, and Circuits, Systems, and Signal Processing (Springer). Her area of expertise is wireless communication, digital signal processing, optimization techniques, and energy harvesting.

Chapter 4

M-Ary Signaling for FSO Under Different Atmospheric Conditions Harsimran Jit Kaur and Rubina Dutta

4.1

Introduction

In the present era when demand for data is ever-growing and the radio frequency spectrum is getting overcrowded, free-space optics (FSO) play a significant role. FSO is an interdisciplinary field that works on principles of both radio and fiber and has seen substantial advances in the recent era. FSO also named optical wireless communication has gotten gigantic consideration because of the expansive unlicensed range that it uses and is proposed to supplement the clogged radio range. It could be said it is “fiber without the fiber” [1]. Alexander Graham Bell has implemented FSO in 1880 when he adjusted sound onto a light emission utilizing his photograph telephone over separation of 213 mts. Presently, FSO can be utilized to communicate many Gbps (gigabits every second) more than a few kilometers. In that capacity, FSO is a potential answer for the alleged “last mile” and “last meter” availability issues, when fiber establishment is too costly [2]. Cuttingedge trial frameworks can support petabits for more than a few meters and terabits every second for more than a few kilometers. The innovation is likewise prominently appropriate where it is difficult to introduce fiber, while simultaneously it is helpful for fast establishment. Giving excellent web availability at a sensible cost will empower creating economies to get to the alleged information economy and help make a “computerized opportunity” [3]. The propagation of FSO is dependent upon a few specialized difficulties. These incorporate divergence of the beam over significant distances, pointing mistakes (the exact arrangement is required), solid air lessening when the climate isn’t clear, and environmental choppiness [4]. There are answers for divergence, arrangement, and attenuation, yet the issue of climatic

H. J. Kaur (*) · R. Dutta Chitkara University Institute of Engineering and Technology, Chitkara University, Patiala, Punjab, India e-mail: [email protected]; [email protected] © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 S. Singh et al. (eds.), Broadband Connectivity in 5G and Beyond, https://doi.org/10.1007/978-3-031-06866-9_4

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choppiness is to a great extent unsolved. During pandemics and following lockdowns or physical removal (e.g., during COVID-19), quick and dependable web availability is particularly urgent to keep up online training for students, empower far-off work openings, and give admittance to online medical care administrations. Potential utilization of FSO correspondence is to expand the limit of the existing microwave foundation [5].

4.2

Background

FSO is a line-of-sight optical light transmission technology for airborne data, voice, and video communications, allowing optical networking without the need for a fiberoptic cable. FSO requires a light source, focused on either light-emitting diodes or laser diodes. Lasers are a simple process close to fiber-optic communication, and the transmission media is the only exception [6]. Light is often more rapid in free than the fiber-optic cable through the air. FSO, also known as open-air photonics or wireless optics, is also known as free-space photonics (FSP) [7]. FSO uses laser beams to transmit data usually ranging from 100 mts to a few kilometers at transmission bandwidths up to 1.25 Gbps at frequencies above 300 GHz wavelengths, typically 785 to 1550 nm, using a line-of-vision optical bandwidth connection [2]. The use of free-space optics wireless networks eliminates the need for secure licenses for RF signal solutions, as well as the high cost of laying fiber-optic cables [3]. An interesting data rate (10 Gbps) has been achieved by research on different optical bands, with visibility separation limited to only 500 mts, that assesses the execution of three optical transmission windows under poor weather conditions, but does not recommend any atmospheric disturbance mitigating methods [8]. In 2018 [9], various forms of advanced modulation are studied. In 2019 [10], a transmit power adjusting transmitter and receiver configuration was used to deal with atmospheric problems, but the plan applies expensive limitations to deal with the channel problems and fix atmospheric problems. Researchers have demonstrated difficulties to send power for FSO [3]. Due to restrictions associated with the use of high power, visible and no visible laser in open-air power cannot be expanded beyond the limit. Optimization of packet size has been proposed for data rate enhancement in FSO [11]. Although packet size can be optimized, however, overall data rate cannot be increased when the signal-to-noise ratio (SNR) is lower than the ordinary packet size. The mitigation method proposed for turbulence cannot be applied to all cases as it does not increase the range of communication [12]. To decrease the between channel cross talk and BER, self-recuperating Bessel beam along with adaptive radiation has been proposed [13]. Phase distortions due to atmospheric disturbances can be handled by incorporating adaptive modulations, but due to the additional processing complexity of coupler and polarizer, this becomes unsuitable for low latency applications [4].

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Although fiber optics has large points of interest, it has been limited to backhaul networks for quite a long time. Reliable and high-bandwidth optical fiber did not benefit from the connection between the end user and the physical link. Work focuses on mitigating the impact of threats in the atmosphere [4]. Recently, OFDM-based free-space radio optics have suggested and indicated an important relation between enhancing the link distance under different weather conditions [14, 15]. Multiplexing to upgrade the data rate or the use of low modulation order to improve reliability can result in high processing time and lower data rate, however. Robust modulation (BPSK) and spatial variety methods [1] are used to tackle FSO environmental turbulence. However, this robust modulation limits the transmission throughput and adds complexity to the receiver. Hence, the area demands more exploration for implementing appropriate signaling techniques that can cope with all these challenges of FSO link with the best quality. FSO communication is equipped for giving link-free correspondence at high information rates up to Gbps. It is a developing zone in recent era days because of its low force, transfer speed versatility, scalable bandwidth range, quick speed of deployment, and cost viability [13]. Ongoing development of FSO is proven by tremendous improvement in communication technology, bringing about examinations of many exciting simulative and experimental implementations. However, the framework is impacted by sudden environmental and climate conditions, resulting in the degradation of the performance of the optical connection. Researchers are exploring solutions and architectures for future efficient FSO communication [14, 16–18]. The dependability of the FSO connection can be improved by building a climatic chamber as a model to concentrate the free-space channel, and its prototype should be made under controlled climatic conditions [19]. To impersonate the open-air ecological conditions, an indoor chamber furnished with fans and warming curl is made up, which gives manual control of the temperature and wind speed inside the chamber. The free space should be described and upgraded to keep a specific strength of disturbance [5]. The exhibition of the connection can be assessed by computing the boundaries like BER and SNR.

4.3

Need of FSO

A major challenge faced by fiber-optic communication system developers is that supplying a separate fiber-optic line to each end user is costly. The optical fiber construction cost is so high and often takes a lot of time, such as getting government grants, trenching, labor costs, etc. [20]. The disparity in operating wavelengths is the main advantage of optical wireless communication systems over radio frequency communication systems. Compared to lasers, the radio frequency (RF) wavelength is much longer. The beam diameter that can be accomplished using lasers is also smaller than that of the RF device. The size of the transmitting and receiving antenna that is required would be large (approximately meters wide) and heavy if an RF

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Table 4.1 Comparative analysis of technologies S. no. 1. 2. 3. 4. 5. 6.

Parameters Throughput Deployment cost Reliability Security Spectrum licensing Calibration

Radio frequency 10 Mbps for 10 mts High Low Less secure 30 khz–300 Ghz No need for alignment

Free-space optics 1.25 Gbps for 1 km Low High Highly secure No spectrum licensing Need proper alignment

system were to be used, compared to using an optical connection that needs an optical antenna of few centimeters. Along with license-free transmission, the data rate provided by FSO is quite higher, whereas RF uses a portion of the spectrum on the other side, so FSO is cheap as compared to RF. RF communication offers less security, but in FSO security is the key feature since information is transmitted in the form of narrow light beams, and it is very difficult to detect narrow light beam [5]. The aim is not to connect every user to the Internet or a wireless network. The need to establish short-range, license-free wireless communication networks in which we can transmit heterogeneous information at any location and at any time has emerged as a necessity for connecting LCDs, home appliances, etc. with the network [3]. Table 4.1 presents the comparative analysis of RF with FSO on parameters such as throughput, cost, reliability, security, licensing, and calibration [20, 21]. Throughput Throughput is the rate of effective messages sent in bps calculated over the channel. RF offers low Mbps throughput at shorter distances, whereas FSO provides Gbps throughput at longer distances on the other hand. Ease of Deployment The cost of deployment in FSO is lower compared to RF communication since the first step in optical fiber communication is to dig and then provide connections via optical fiber from the transmitter to receiver. But in the FSO, digging and trenching are not required. It is therefore simpler and cheaper to mount FSO communications compared to wired systems. Security The FSO’s biggest advantage compared to RF is its security. Spectrum analyzer, digital storage oscilloscope, etc. do not detect FSO light beam; it is very difficult to jam an optical receiver because of its narrow beam. License-Free Operation Radio frequency systems are constrained by bandwidth, but FSO systems are license-free. Calibration FSO works the line of sight between the transmitter and the receiver. So in FSO contact is possible only when the transmitter and receiver are properly aligned (Fig. 4.1). Due to these advantages, people prefer to adopt the FSO-based system as compared to other communication systems.

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Fig. 4.1 Benefits of FSO

4.4

System Description

Primarily as shown in Fig. 4.2, FSO consists of three major parts: transmitter, freespace medium, and receiver. The transmitter consists of a light source (LED, LASER, and IR); the receiver consists of a photodetector (PIN and avalanche photodiode) [17]. Data at the transmitter end can be modulated using varying M-ary modulation techniques. Although various M-ary signaling can be applied to transmit data over FSO link, however, this chapter uses 256 quadrature amplitude modulation orthogonal frequency-division multiplexed (QAM-OFDM) transmissions for enhanced data rate and better BER efficiency. A clear line of site between transmitter and receiver is required to achieve the FSO. To cope up with atmospheric noise effects, the FSO transmitter needs high power to provide the signal’s strong intensity. FSO works predominantly in two bands of frequency, such as 780–900 nm and 1500–1600 nm. In contrast to 1500–1600 nm, the LASER that is mostly used at 780–900 nm is less costly [2]. But it is primarily used for moderate distances according to its strength level. Besides, the 1500–1600 nm band is used for longdistance communication but provides poor transmitting characteristics to the receiver. FSO transmitters are mounted on the rooftop of the building [20]. The present model is using a laser as a source on the transmitter side and photodetectors on the receiver side. In contrast to RF facilities, this optoelectronic system is inexpensive. IR transmission, on the other hand, never penetrates the walls

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Fig. 4.2 Block diagram of FSO communication system

Fig. 4.3 Optical OFDM block diagram for FSO

and provides high protection. It is not regulated by the Federal Communications Commission (FCC) regulations. It transmits a very small beam of data that is hard to detect. OFDM transmits information from high-speed data by separating it into lower data rate blocks. For various fiber types, the optical OFDM transmitter may be altered, with different network ranges from short to long haul with different detection types, viz., direct or coherent detection. The system can be configured to provide versatility in the bit rate using different depths of modulation. A block diagram for OFDM optical transmission is illustrated in Fig. 4.3. To encrypt the data, the model uses Fourier transform methods, where data information is carried over several lower-rate subcarriers. The transmitter segment requires the conversion of highrate data into N parallel low data rate paths where data can be modulated using different digital modulation techniques such as QPSK, 16-QPSK, M-ary QAM, etc. [18] on each path.

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High spectral efficiency can be achieved by different modulation choices in the M-QAM format [14]. In long-haul systems, M-QAM emerges as a potential candidate to achieve high data rate transmission. Transmission using QAM modulates half symbols using one frequency known as in-phase component and the other half symbols at the equivalent frequency with a phase gap π/2 known as a quadraturephase component [14]. Finally, the addition of both components generates the QAM signal. Increasing the value of M increases the number of bits per symbol, allowing the spectrum to have a narrowing effect. As the value of M rises from 16 [12], the spectral efficiency increases from 64 to 256 because of an increase in the number of bits per symbol. The increase in M-value, however, makes the symbol similar to neighboring symbols, which leads to an increase in errors due to noise and interference as more symbols are transmitted, and thus the error rate increases. Thus, BER performance may reduce with an increase in the value of M, but spectral efficiency can be enhanced with an increase in the order of M-QAM [15]. Using an IFFT for the generation of the dense comb of OFDM subcarrier frequencies [22], the basic requirement of the OFDM system for multiple microwave mixers generating different subcarrier frequencies has been met. At the transmitter, serial to parallel conversions are carried out to transform randomly generated highrate data into low data rates. Digital data is used in the modern era of communication to represent data for storage and transmission [22]. Every symbol representing digital data is associated with a certain signal state in digital data modulation. Optical signal information is encoded during optical transmission according to intensity, phase, or frequency. To meet the continued explosive demand for bandwidth, it is very important to have an expanded optical transport capability by using spectrally more effective modulation formats [23]. Improving the number of bits transmitted per symbol is a major concern for the implementation of advanced modulation formats. This change to the number of bits per symbol enhances spectral efficiency, but this increase can be made to the relation permit point SNR. Amplitude-shift keying (ASK) is a modulation format category that makes use of multiple-level amplitude to allow multiple bits per symbol to be transmitted. Multilevel phase shifts can be used to represent multi-bits per symbol in another modulation format known as phase-shift keying (PSK). Merging these two degrees of freedom, i.e., several amplitude and phase levels called QAM, increases the symbol size and enables the transmission of more bits per symbol [24]. The number of symbols, M, which can be transmitted with several bits per symbol, m, is related to expression (4.1): m ¼ log 2 M

ð4:1Þ

The implementation of amplitude and phase modulation on the optical signal imposes cost and complexity constraints [25]. Alternations for subcarriers in the RF domain are accommodated as an alternative to encoding phase and amplitude information in the optical domain, and then the optical carrier amplitude is modulated using direct or external modulation. However, because As the modulation

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format order increases, the OSNR requirements and the sensitivity to nonlinear distortion increases which further limits the reach. It is possible to increase this transmission distance by compensating for the impairments that arise during propagation. The transmission distance mustn’t be sacrificed to satisfy the increased bandwidth demand and have higher bit rates. This chapter discusses M-ary OOFDM transmissions using direct detection in spectrally efficient modulation formats. OFDM data is generated using a pseudo-random generator producing 9600 bits with FFT size 64 and coding rate ¾. 256 QAM (encoding 8 bits per symbol) with data rate of 36.86 Gb/s is experimented over OFDM transmission system for FSO.

4.5

Result and Discussion

This section represents the comparative analysis of the proposed 256 QAM-OFDM system on the FSO link over the varied ranges, beamwidth, and power. Based on analysis of these parameters, optimized value for the power and beamwidth is taken up and analyzed over varying weather conditions such as clear, haze, and foggy conditions.

4.5.1

Q-Factor and BER Analysis over Varied Ranges

Table 4.2 presents the comparative analysis of Q-factor and BER over the varying ranges for channels 1, 5, and 8. Figure 4.4 summarizes the Q-factor over varied distances for channels 1, 5, and 8. The BER results are analyzed using eye diagrams. Also, the graphical representation of the results in terms of eye diagram is shown in Fig. 4.5, which indicates that eye height is maximum at 400 mts as compared to 800 mts, 1000 mts, and 1500 mts producing BER 2.07*10127, 3.87*10023, 4.25*10009, and 1 and Q-factor 23.97, 9.83, 5.7, and 1, respectively, for channel 1. BER and Q-factor have improved to 5.27*10131 and 24.32 for channel 5 due to reduced intersymbol interference. However, as the number of channels increases from 5 to 8, there is degradation in BER to 1.25*10107,2.84*10021, and 6.85*10009, respectively. Reduction in BER with the rise in a number of channels Table 4.2 Comparative analysis based on quality factor and BER over varying ranges Range (in mts) 400 800 1000 1500

Channel 1 Q-factor 23.97 9.83 5.7 0

BER 2.07*10127 3.87*10023 4.25*10009 1

Channel 5 Q-factor 24.32 10.02 5.82 0

BER 5.27*10131 5.99*10024 2.89*10009 1

Channel 8 Q-factor 22.009 9.39 5.69 0

BER 1.25*10107 2.84*10021 6.85*10009 1

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Quality-Factor

Distance Vs Q-Factor

Distance (in kms) Fig. 4.4 Graphical representation of Q-factor over varied ranges

Fig. 4.5 Eye pattern over (a) 400 mts, (b) 800 mts, (c) 1000 mts, (d) 1500 mts

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can be attributed to the fact aliasing effect. Reduced eye opening can be attributed to the fact that the signal is highly affected by noise and this is not acceptable while transmitting information from one point to another. With the increase in range, atmospheric effects and scintillations are degrading the signal strength.

4.5.2

Q-Factor and BER Analysis over Varying Beamwidth

Table 4.3 and Fig. 4.6 show the analysis between quality factor and BER over varying beamwidth of the signal. For channel 1, beamwidth is 0.1, and it produces a 14.10 quality factor with the BER of value 1.84*10045. On the other hand, if the beamwidth is 0.2, then it produces a 5.7 quality factor with the BER of value 4.25*10009. The overall performance of the system depicted that 0.2 mrad beamwidth offers the system performance up to acceptable BER. The more the beamwidth, the more the signal is scattered and the more is the dispersion which reduces the quality factor and increases the BER. This can be attributed to the fact that the narrower the beamwidth, the more focused is the signal and the longer the distance it can travel. With the rise in number of channels from 1 to 5, there is improvement in BER, but as it increases to 8, the BER degrades. This can be attributed to the fact that some of these channels lead to intersymbol interference.

Table 4.3 Comparative analysis on the basis of quality factor and BER over varying beamwidth

Quality-Factor

Beamwidth (in mrad) .05 .1 .15 .2

Channel 1 Q-factor 22.51 14.10 8.7 5.7

BER 1.36*10112 1.84*10045 1.13*10083 4.25*10009

Channel 5 Q-factor 22.86 14.33 8.89 5.82

BER 4.6*10116 2.88*10047 2.84*10019 2.89*10009

Beamwidth Vs Q-Factor

Beamwidth (in mrad) Fig. 4.6 Graphical representation of Q-factor over varied beamwidth

Channel 8 Q-factor 20.60 13.13 8.4 5.69

BER 1.120*10094 1.02*10039 1.95*10017 6.85*10009

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Q-Factor and BER Analysis over Varying Power

To make the system cost-effective, its power should be optimized. With the increase in power, the laser intensity increases which increases the distance factor and also provides better tolerance to atmospheric turbulences. But after a certain threshold value, a high-power laser introduces some nonlinear effects which reduce the quality factor of the system. There is always a compromise between the power and the distance of the laser. Table 4.4 and Fig. 4.7 investigate the comparative analysis of quality factor and BER over varying power for channel 1, channel 5, and channel 8, with the aim to select optimized value of power. With the increase in power, there is a considerable improvement in its Q-factor and decrement in BER. When power is 20 dBm, Q-factor is 0 and BER value lies to 1. But when power is 4 dBm, the value of Q-factor increases to 7.58, 7.22, and 7.36 for channel 1, 5, and 8 with BER 1.63*10014, 2.44*10013, and 8.7*10014, respectively. This can be attributed to the fact that as power increases, the laser intensity increases producing improved BER; however, further increase in power leads to enhancement in nonlinearities and reduction in Q-factor and BER. Thus, the optimized power chosen for the present system is 4 mW.

Table 4.4 Comparative analysis on the basis of quality factor and BER over varying power Power (in mw) 0 1 2 4

Channel 1 Q-factor 3.75 3.90 4.88 7.58

BER 0.0009375 4.78*10005 5.09*10007 1.63*10014

Channel 5 Q-factor 2.87 3.65 4.62 7.22

BER 0.00210973 .0001262 1.8*10006 2.44*10013

Quality-Factor

Power Vs Q-Factor

Power (in mW) Fig. 4.7 Graphical representation of Q-factor over varied power

Channel 8 Q-factor 3.15 3.91 4.85 7.36

BER 000805139 4.45*10-005 5.89*10007 8.7*10014

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16-Channel 256 QAM-OFDM System

Once the value of beamwidth and power has been optimized, then these values are utilized to build 256 QAM-OFDM system for 16 channels. The atmospheric effects play a significant role in FSO transmitter system, and it has been analyzed over varying weather conditions. These weather conditions have been selected, viz., clear, haze, and fog conditions. Eight-channel 256 QAM-OFDM gives the channel capacity of 320 Gbps with the frequency spacing of 100 GHz. Beyond this, the system produces the nonlinear effects. In order to remove the problem of eight-channel 256 QAM OFDM, a system is modified to produce the channel capacity of 640 Gbps with the channel spacing of 50 GHz. Laser array is used in producing wavelength’s difference between the adjacent laser of 50 GHz. Table 4.5 represents the system performance under various environmental conditions at acceptable BER. System has been analyzed under the effects of clear weather, haze, and fog over varying ranges with attenuation factor of 0.1 dB/km, 4 dB/km, and 22 dB/km, respectively. Under clear weather conditions, up to 4-km system produces very small of BER, and after this, when the distance increases, then automatically BER increases. Till 30-km system produces results with acceptable BER. Under haze conditions, the system produces acceptable BER at 1 km, and after this, when the distance increases, then BER increases. Similarly in fog condition, up to 0.5-km system produces results with acceptable BER, and beyond this system, quality factor drastically degrades and produces poor BER. Designed system offers higher channel capacity with the help of polarization interleaving technique that efficiently utilizes the spectrum and increases the total capacity of the system. Figure 4.8 reveals that FSO link prolongs to 20 km with acceptable quality factor in case of clear weather and degrades to 4 km and 1.1 km in case of haze and fog conditions, respectively. In comparison with existing FSO technologies, proposed system is more immune to atmospheric impact, such as fog, and brings incomparable improvement. Our system provides great potential to solve bottlenecks that have in the past hindered its Table 4.5 Analysis over varied weather conditions Distance (in km) 0.1 0.5 1 2 3 4 5 10 20 30

Clear weather Q-factor BER 137.57 0 112.56 0 90.43 0 63.87 0 48.89 0 39.36 0 32.76 1.46*10233 16 5*10064 7.32 7.8*10014 4.02 2.08*10005

Haze Q-factor 134.82 97.9 64.62 29.16 13.69 2.97 0 0 0 0

BER 0 0 0 1.5*10187 3.4*10043 6.44*10011 0.0011 1 1 1

Fog Q-factor 121.625 43.56 9.05 0 0 0 0 0 0 0

BER 0 0 1.33*100311 1 1 1 1 1 1 1

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Fig. 4.8 Graphical representation of Q-factor over varied beamwidth

application, such as distance, latency, and reliability limits. In the future, we might also build a key piece of infrastructure crucial to bringing high-bandwidth communications to rural areas across the globe, along with the 5G network in urban areas such as Eindhoven. For remote areas of the world where fiber-optic networks are not technically or economically feasible to build, FSO may be a permanent solution. System BER is analyzed in terms of eye patterns as eye diagrams depict the interference level at the output. The system produces best results when the opening of the eye is maximum, so according the eye height, optimum results have been analyzed. As per Fig. 4.9a, b, at 20 km, the eye height is 6.38*10007, whereas for 40 km, the eye height is 6.13*10009. The maximum eye height is obtained at the range of 20 km which infers small interference and noise effect. Figure 4.9c, d represent the eye pattern for foggy weather condition. At 4 km, the eye height is 4.69*10007; on the other hand, for 6 km, the eye height is 0. The maximum eye height is analyzed at 4 km which infers that it is optimized distance under foggy weather condition. Further, the eye pattern for worst weather condition has been analyzed in Fig. 4.9e, f. FSO system has been analyzed up to the distance of 1.1 km under the worst weather condition and produces the eye height of 4.68*10007. But if we increase the range beyond 1.1 km, then it produces high intersymbol interference. From the analysis, it summarizes that under haze condition, the proposed system outperforms with 2 km with BER 1.5*10187 and Q-factor 29.16. Results are good till 3 km with BER 3.4*1043 and Q-factor 13.69. System results are acceptable till 4 km with BER 6.44*1011, but beyond that, the system performance degrades. When atmospheric conditions are foggy, then the system performance is acceptable till 1 km with BER 1.33*1031 and Q-factor 9.05; beyond that, atmospheric effect has degraded the system performance. Under clear weather condition, the system performance is acceptable till 20 km with BER 4.8*1014, whereas this range is 4 km for haze and 1.1 km for fog condition.

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Fig. 4.9 Evaluation of eye diagram at (a) 20 km under clear weather conditions (b) 40 km under clear weather conditions, (c) 4 km under haze condition, (d) 10 km under haze condition, (e) 1.1 km under foggy weather conditions, (f) 8 km under foggy weather conditions

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4.6

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Conclusion

This chapter presents the latest developments in evolving free-space optics (FSO) technology. It presents the FSO’s basics along with technical knowledge of the state of the art in the domain. FSO connectivity is a realistic option for building a regional wireless networking system in three dimensions, providing bandwidths far beyond what is feasible in the radio frequency (RF) spectrum. This chapter models 256 QAM OOFDM system for FSO transmissions and analyze channel behavior under practical atmospheric conditions. Under clear weather conditions, the system performance is acceptable till 20 km with BER 7.8*10014, whereas this range is 4 km for haze and 1 km under foggy conditions.

References 1. G.G. Lema, Free space optics communication system design using iterative optimization. J. Opt. Commun. (2020) 2. Shaina, A. Gupta, Comparative analysis of free space optical communication system for various optical transmission windows under adverse weather conditions. Procedia Comput. Sci. 89, 99–106 (2016) 3. S. Chaudhary, A. Amphawan, The role and challenges of free-space optical systems. J. Opt. Commun. 35(4), 327–334 (2014) 4. M.S. Khan, S. Ghafoor, J. Mirza, S.M. Hassan Zaidi, Review of studies that integrate the free space optics with fiber optics, in HONET-ICT 2019 – IEEE 16th International Conference on Smart Cities Improving Quality Life using ICT, IoT AI (2019), pp. 74–79 5. K. Kaur, R. Miglani, G. Singh, Communication theory review perspective on channel modeling, modulation and mitigation techniques in free space optical communication. Int. J. Control Theory Appl. 9(Special issue 11), 4969–4978 (2016) 6. A. Kaur, Review paper: free space optics. Int. J. Adv. Res. Comput. Sci. Softw. Eng. 4(8), 969–976 (2014) 7. T. Nagatsuma, G. Ducournau, C.C. Renaud, Advances in terahertz communications accelerated by photonics. Nat. Photonics 10(6), 371–379 (2016) 8. V. Sharma, G. Kaur, Degradation measures in free space optical communication (FSO) and its mitigation techniques – a review. Int. J. Comput. Appl. 55(1), 23–27 (2012) 9. M.K. El-Nayal, M.M. Aly, H.A. Fayed, R.A. AbdelRassoul, Adaptive free space optic system based on visibility detector to overcome atmospheric attenuation. Results Phys. 14, 102392 (2019) 10. G. Alnwaimi, H. Boujemaa, K. Arshad, Optimal packet length for free-space optical communications with average SNR feedback channel. J. Comput. Netw. Commun., 2019 (2019) 11. K. Sunilkumar, N. Anand, S.K. Satheesh, K. Krishna Moorthy, G. Ilavazhagan, Performance of free-space optical communication systems: effect of aerosol-induced lower atmospheric warming. Opt. Express 27(8), 11303 (2019) 12. S. Li, J. Wang, Adaptive free-space optical communications through turbulence using selfhealing Bessel beams. Sci. Rep. 7(August 2016), 1–8 (2017) 13. S. Parween, A. Tripathy, Free space optic communication using optical AM, OOK-NRZ and OOK-RZ modulation techniques, in 2019 3rd International Conference on Electronics, Materials, Engineering and Nano-Technology, IEMENTech (2019)

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14. M. Singh, J. Malhotra, Performance comparison of M-QAM and DQPSK modulation schemes in a 2  20 Gbit/s–40 GHz hybrid MDM–OFDM-based radio over FSO transmission system. Photon Netw. Commun. 38(3), 378–389 (2019) 15. G.G. Lema, T.B. Reda, D.H. Hailu, LTE quality of service enhancement under OFDM modulation techniques. Wirel. Pers. Commun. 113(2), 995–1008 (2020) 16. M.M. Abadi, Z. Ghassemlooy, M.R. Bhatnagar, S. Zvanovec, M.A. Khalighi, A.R. Maheri, Using differential signalling to mitigate pointing errors effect in FSO communication link, in 2016 IEEE International Conference on Communication Work. ICC (2016), pp. 145–150 17. K.A. Balaji, K. Prabu, Performance evaluation of FSO system using wavelength and time diversity over Malaga turbulence channel with pointing errors. Opt. Commun. 410(November 2017), 643–651 (2018) 18. A. Mostafa, S. Hranilovic, In-field demonstration of OFDM-over-FSO. IEEE Photon. Technol. Lett. 24(8), 709–711 (2012) 19. A. Prokes, Atmospheric effects on availability of free space optics systems. Opt. Eng. 48(6), 066001 (2009) 20. R. Dutta, H. Kaur, A review on free space optics – solution for high bandwidth. Data Eff. Transm. Syst. 7109, 53–56 (2014) 21. R.A. Alsemmeari, S.T. Bakhsh, H. Alsemmeari, Free space optics vs radio frequency wireless communication. Int. J. Inf. Technol. Comput. Sci. 8(9), 1–8 (2016) 22. I. Jaiswal, R.G. Sangeetha, M. Suchetha, Performance of M-ary quadrature amplitude modulation -based orthogonal frequency division multiplexing for free space optical transmission. IET Optoelectron. 10(4), 156–162 (2016) 23. J. Kaur, R. Miglani, J.S. Malhotra, G.S. Gaba, Performance analysis of M-ary QAM modulated FSO links over turbulent AWGN channel. Int. J. Appl. Eng. Res. 10(15), 35322–35327 (2015) 24. T.Y. Elganimi, Studying the BER performance, power- and bandwidth- efficiency for FSO communication systems under various modulation schemes, in 2013 IEEE Jordan Conference on Applied Electrical Engineering and Computing Technology, AEECT (2013), p. 5 25. M. Ashraf, G. Baranwal, D. Prasad, S. Idris, M.T. Beg, Performance analysis of ASK and PSK modulation based FSO system using coupler-based delay line filter under various weather conditions. Opt. Photonics J. 8(8), 277–287 (2018)

Dr. Harsimranjit Kaur received her PhD from Chitkara University in 2016 and MTech in electronics and communication engineering from DAVIET, Jalandhar, in 2009. She joined teaching in 2005 at Engineering College Amritsar. She is presently working as an associate professor in the Department of Electronics and Communication Engineering, Chitkara University, Punjab. She has been engaged in research on optical communication since 2009 and has successfully completed various projects, which includes developing an intelligent software–defined optical transmission by making system dynamically adaptable and reconfigurable for performance improvement. Her major research interests are nano photonics, integrated photonics, and fiber-optic transmission systems. She has authored and co-authored more than 45 refereed papers in international journals and conference contributions. She has 9 patents to her credit. Rubina Dutta is pursuing her PhD from Chitkara University, Rajpura, Punjab, in the area of augmented reality for engineering education. She is an assistant professor at Chitkara Institute of Engineering and Technology, Chitkara University, Punjab. Her research interests include human‐ computer interaction, IoT and embedded systems, and innovative teaching‐learning strategies.

Chapter 5

Multiple Input-Multiple Output Antenna for Next-Generation Wireless Communication Manish Sharma

5.1

Introduction

The 5G communication system is a reality now with partial deployment achieve first phase. The expectation has executed around 20% of what was declared earlier to 5G mmWave applications [1]. As of now, 5G deployment for sub-6GHz has been deployed where long-term evolution (LTE) and long-term evolution advanced (LTE-A). The 5G deployment has been already associated with multiple inputmultiple output (MIMO) and forms an integral part. It is also known that the path loss increases as the operating frequency increases, and hence it is much tougher to mitigate from existing 3G/4G to 5G mmWave networks. There are different bands proposed for mmWave applications which include 25.25 GHz–29.50 GHz and 36.00 GHz–40.50 GHz bands [2]. Dielectric resonator antennas (DRAs) play a major role in designing antennas for mmWave applications where cylindrical, rectangular, hemispherical, hexagonal, conical, triangular, and trapezoidal DRAs are used [3]. A sub-6GHz 5G MIMO provides better isolation where a stub is attached to the ground [4]. A dual-band 5G MIMO antenna which is obtained by modifying rectangular patch results in good isolation [5]. A low-profile antenna for 5G application is reported for lower-band (3.40 GHz–3.80 GHz) application [6]. In the future, smartphones will be embedded with the latest 5G technology for applications at mmWave which will increase the transmission data rate [7]. Also, by using a metasurface, 28 GHz MIMO antenna with circular polarization resulted [8]. The deployment of a 5G network faces different challenges like the deployment of cells in the wireless network [9] and the requirement of a complex control system [10]. Also, from rectangular monopole resonating at 28 GHz, the dual band centered at 28GHz/38GHz is obtained by modification of path [11]. 5G system has the

M. Sharma (*) Chitkara University Institute of Engineering and Technology, Chitkara University, Rajpura, Punjab, India © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 S. Singh et al. (eds.), Broadband Connectivity in 5G and Beyond, https://doi.org/10.1007/978-3-031-06866-9_5

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capability of transmitting the data with a speed of 20 Gbps with the capacity of the area being 10 Mbps/m2 [12]. Graphene-based 5G antenna is fabricated and tested for 28 GHz/38 GHz applications [13]. A dual-mode 5G MIMO antenna provides a gain of 10.50 dBi and also provides directional beamforming in the azimuth plane [14]. This technology is useful for a smarter healthcare system where IoT is used [15, 16]. A 20 GHz array antenna provides a peak gain of 12.15 dBi with radiating efficiency of 85% providing a narrow beamwidth of 44.3
and 12.5
in principal planes [17–21]. A 55 frequency selective surface antenna is useful for 60 GHz mmWave, and 5G antenna utilizing graphene satisfies the needs such as greater channel capacity, widespread spectrum with high gain, and ability to steer [22, 23]. A 44 MIMO antenna with four identical radiating patches provides operational bandwidth from 23 GHz to 40 GHz covering mmWave applications [24], and a dual-band MIMO antenna is designed on Rogers RT/duroid 5880 substrate which also resonates at 28 GHz/38 GHz bands [25]. Applying slotted multiple resonance microstrip patch is achieved providing broader bandwidth and wide angular coverage [26–29]. A MIMO antenna is developed where spatial diversity technique is used for 28 GHz mmWave applications [30]. In this proposed chapter, the design methodology of 5G MIMO antenna at sub-6 GHz and 28 GHz/38 GHz is discussed.

5.2

Development and Analysis of 5G MIMO Antenna for 28/38GHz

The shortage of bandwidth in the wireless communication system was the motivation factor for the establishment of the new network which can provide very high data rate transmission with very latency. To execute the above features, 5G wireless communication is being deployed which has advantages of data rate up to 10 Gbps and latency with 1ms but also faces challenges due to a shorter range of communication increasing the need for more repeaters. The upcoming scenario in 2020–2021 will mark the commercial launch of the 5G applications. South Korea already has the experience of 5G services as the country deployed this technology in the 2018 Olympic Games. The 5G band works both in low frequency (sub-6 GHz) and higher bands including 28 GHz, 38 GHz, 60 GHz, and 70 GHz. Lots of research have already been published under the lower sub-6 GHz band, and thus the upper 5G band becomes more important which has to be explored. The MIMO (multiple inputmultiple output) technology becomes more important as it is one of the integral parts of the 5G technology. The deployment of 5G faces challenges such as power that can reach 300 m at 2 GHz and that can reach only 6 m at 100 GHz. The path loss is also one of the major problems in 5G corresponding to approximately 114 dB at 100 GHz frequency [1].

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The solution for the above problems is encountered by the concept of beamforming. The radiated power of the antenna is added up by the gain factor in the intended direction compensating the path loss. Beamforming in the case of radiating antennas is achieved by increasing the number of radiating antennas with equal power, and the magnitude of the radiated signal will add up in one direction, and the destructive signal will cancel with each other. To understand the working of 5G MIMO antenna at 28 GHz/38 GHz band, a 22 MIMO antenna is studied [11]. Figure 5.1 illustrates the study of a single and 22 MIMO antenna which is designed for dual-band operation working at 28 GHz and 38 GHz bands. The antenna design is initiated by considering a rectangular patch that provides resonance at 28.7 GHz and 40.5 GHz. To achieve the required dual-band operation, the rectangular patch is modified which provides the resonance at 28 GHz and 38 GHz which is required for 5G applications shown in Fig. 5.1a. The rectangular slot in the rectangular ground plane observed in Fig. 5.1b helps in the improvement of the matching of the impedance. Figure 5.1c, d shows the perspective view of the antenna connected with the SMK connector which is capable of working up to 60 GHz in real-time applications. Single-element antenna is printed on Rogers RT/duroid substrate of thickness 0.38 mm (permittivity, 2.20; loss tangent, 0.0009). Figure 5.2a

Fig. 5.1 (a) Front view of dual-band antenna. (b) Ground view. (c) Perspective view of singleelement dual-band antenna. (d) Perspective view of 22 MIMO dual-band antenna

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Fig. 5.2 (a) S-Parameter of the single radiating antenna (S11). (b) S-Parameter of 22 MIMO antenna (S11/S12/S21/S22)

shows the S-parameter which is obtained for a single radiating antenna covering 28 GHz and 38 GHz band for 5G applications. Figure 5.2b provides the S-parameter for a two-port MIMO antenna where both the radiating antennas cover 5G bands. Also, the isolation between the input ports is very good with values of isolation S12/ S2195 78 86 Not given

Gain (dBi) 3.55 5.00 5.70 9.85 1.27 1.83 7.20–7.90

85 70

5.92–6.12 26–29.5 25.5–29.6 25.1–37.5 27.5–28.35

71 83 80 >80 80

12.15 10.58 8.87 11.45 5.13 9.53 8.02 10.6 6.85

Fig. 5.4 (a) Advancement of mobile communication from 1G to 5G. (b) Application of 5G technology

communication network constitute base stations, user equipment (mobile phones), and the core network. 1G technology or the first-generation mobile system which utilized only voice communication system based on frequency-division multiplexing (FDM) was used with the maximum data rate of 2.4 kbps. 2G technology witnessed the utilization of code-division multiple access (CDMA) and time-division multiple access (TDMA) with data rate speed being between 14.4 kbps and 64.0 kbps. Similarly, 3G and 4G systems were able to include applications such as multimedia messaging service (MMS), short message services (SMS), worldwide interoperability for microwave access (WiMAX), long-term evolution (LTE), and advanced LTE (LTE-A) achieving a data rate of 2 Mbps and 100 Mbps, respectively. The deployment of 5G on the other hand is in the implementation stage, and compared with the previous counterpart, 4G technology is 100 times faster. The 5G technology has the capability of working for numerous applications involving the Internet of Things

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(IoT) shown in Fig. 5.4b. The key features of 5G technology include the data rate up to 10Gbps, latency as lower as 1ms, good IoT connectivity, enhancement in AR (augmented reality)-VR (virtual reality) applications, artificial intelligence, broadcasting data supporting approximately 65,000 connections, and excellent battery support system for low-power IoT devices. 5G deployment also faces a few challenges such as the utilization of frequency bands up to 300 GHz leading to costlier wireless carriers, shorter wavelength traveling to short distance and hence increasing the number of base stations, new device deployment supporting 5G, and providing new dimensions to cyber laws.

5.4

Scope of Recent Research

The benefits of 5G technologies are immense, but their deployment focuses on several challenges which lead to the research gap and has to be explored. This opens up the gateway for various challenges which include pilot contamination, estimation of the channel, pre-coding, user scheduling, and impairments of hardware for better utilization. Efficiency of the spectral energy and detection of the signal are the few to name them. In a massive MIMO system, a larger number of antennas are required to reduce the effect of noise, fading of signal, and multiple path interference. This increases the complexity of the antenna system, thereby increasing the cost. The complexity of the computational analysis and hardware size however needed to be reduced and hence becomes one of the areas of future research in MIMO deployment. However, on the other hand, low-cost equipment may lead to imperfections in hardware such as phase noise, noise due to magnetization, and distortion in the amplifier. Compensation in algorithms may be developed to reduce the hardware impairment which is the new scope for research. Also, contamination of pilots is another problem to be mitigated because of the use of a limited number of orthogonal pilots. Contamination of the pilot increases the interference which affects achieving the throughput. Hence, an optimal method to reduce the problem of contamination of pilots is the new field of research. The computational complexity is however increased in the new deployment of the 5G MIMO system, and hence extra computation is required. Thus, the new technique in pre-coding technique is another scope of research for 5G deployment. Another scope of research in %g technology is scheduling of the user which indicates that the number of users becomes more than the number of antenna terminals available at the base station. With the help of good channel conditions, the throughput of the MIMO system can be increased by scheduling the user experiences. This is also the new area of the research where proper scheduling of users will be satisfied by the number of antenna terminals. Another problem that is faced in the deployment of 5G technology is the reduced throughput of spectral efficiency. This is due to the presence of a larger number of antennas which increases the complexity in computation creating interference due to the detection of the uplink signal system. This signifies that a newer algorithm is required to decrease the complex uplink signal detection algorithm

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which opens up the new field of research to deploy 5G technology. Another exciting research area is a prediction of the statistical channel characteristics which will be implemented by using machine learning and deep learning algorithms. Machine learning algorithm will help in the estimation of MIMO channel, scheduling of users, smarter beamforming, and effective detection of the signal at the receiver side.

5.5

Conclusions

This chapter focused on the latest 5G technology deployment, their advantage, and the challenges they are going to encounter. The analysis of the 5G MIMO antenna was also studied in frequency and diversity performance. The values of ECC, DG, TARC, and CCL were well below the permissible values indicating good transmission of the MIMO antenna. Also, the comparison of the 5G antenna was compared with the present state of the art. All generation technology (1G–5G) was also discussed with the advantage of 5G communication finding applications in the field of IoT, AR-VR, and artificial intelligence. The 5G communication ensures data rate up to 10Gbps with a very low latency of 1ms. The recent scope of research was also listed, and the research gap in the 5G MIMO antenna system concluded that the deployment of the 5G technology will not so easy and will need some more time to come into existence as per the available information.

References 1. M.A.B. Abbasi, Q.H. Abbasi, Development challenges of millimeter-wave 5G beamformers. The Essential 5G Reference Online, 1–25 (2020) 2. A.M. Abdalla, J. Rodriguez, I. Elfergani, A. Teixjeira, Millimeter wave antenna design for 5G applications. Optic. Wireless Converg. 5G Netw. IEEE, 139–156 (2019). https://doi.org/10. 1002/9781119491590.ch7 3. P.R. Meher, B.R. Behera, S.K. Mishra, Design and its state-of-the-art of different shaped dielectric resonator antennas at millimeter-wave frequency band. Int. J. RF Microwave Comput. Aided Eng. 30(7) (2020) 4. A.K. Saurabh, M.K. Meshram, Compact sub-6 GHz 5G- multiple-input-multiple-output antenna system with enhanced isolation. Int. J. RF Microwave Comput. Aided Eng. 30(8) (2020) 5. W. Ali, S. Das, H. Medkour, S. Lakrit, Planar dual-band 27/39 GHz millimeter-wave MIMO antenna for 5G applications. Microsyst. Technol. 27(1), 283–292 (2020) 6. A. Biswas, V.R. Gupta, Design and development of low profile MIMO antenna for 5G new radio smartphone applications. Wirel. Pers. Commun. 111(3), 1695–1706 (2019) 7. W. Hong, K.-H. Baek, S. Ko, Millimeter-wave 5G antennas for smartphones: overview and experimental demonstration. IEEE Trans. Antennas Propag. 65(12), 6250–6261 (2017) 8. N. Hussain, M.-J. Jeong, A. Abbas, N. Kim, Metasurface-based single-layer wideband circularly polarized MIMO antenna for 5G millimeter-wave systems. IEEE Access 8, 130293–130304 (2020)

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9. M.H. Alsharif, R. Nordin, Evolution towards fifth generation (5G) wireless networks: Current trends and challenges in the deployment of millimetre wave, massive MIMO, and small cells. Telecommun. Syst. 64(4), 617–637 (2016) 10. M. Gul, E. Ohlmer, A. Aziz, W. McCoy, Y. Rao, Millimeter waves for 5G: From theory to practice, in Signal Processing for 5G: Algorithms and Implementations (2016), pp. 322–353 11. M.N. Hasan, S. Bashir, S. Chu, Dual band omnidirectional millimeter wave antenna for 5G communications. J. Electromagn. Waves Appl. 33(12), 1581–1590 (2019) 12. S. He, Y. Huang, An introduction on millimeter wave communications. Wiley 5G Ref, 1–23 (2019) 13. J.H. Lee, S.H. Lee, D. Kim, C.W. Jung, Transparent antenna using a μ-metal mesh on the quarter glasses of an automotive for DMB service receiving. Microw. Opt. Technol. Lett. 60(12), 3009–3014 (2018) 14. M. Nouri, S. Abazari Aghdam, A. Jafarieh, J. Bagby, S. Sahebghalam, A wideband millimeterwave antenna based on quasi-Yagi antenna with MIMO circular array antenna beamforming for 5G wireless networks. Microw. Opt. Technol. Lett. 61(7), 1810–1814 (2019) 15. A. Ahad, M. Tahir, M. Aman Sheikh, K.I. Ahmed, A. Mughees, A. Numani, Technologies trend towards 5G network for smart health-care using IoT: a review. Sensors (Basel) 20(14) (2020) 16. S.S. Singhwal, B.K. Kanaujia, A. Singh, J. Kishor, L. Matekovits, Multiple input multiple output dielectric resonator antenna with circular polarized adaptability for 5G applications. J. Electromagn. Waves Appl. 34(9), 1180–1194 (2020) 17. H. Ullah, F.A. Tahir, A broadband wire hexagon antenna array for future 5G communications in 28 GHz band. Microw. Opt. Technol. Lett. 61(3), 696–701 (2019) 18. Q. Wu, H. Wang, W. Hong, Millimeter-wave antenna designs. Wiley 5G Ref, 1–25 (2019) 19. C. Yu, W. Hong, Millimeter-wave RF designs. Wiley 5G Ref, 1–19 (2019) 20. Y. Zhang, J.-Y. Deng, M.-J. Li, D. Sun, L.-X. Guo, A MIMO dielectric resonator antenna with improved isolation for 5G mm-wave applications. IEEE Antennas Wireless Propag. Lett. 18(4), 747–751 (2019) 21. S.N.H. Sa’don, M.R. Kamarudin, F. Ahmad, M. Jusoh, H.A. Majid, Graphene array antenna for 5G applications. Appl. Phys. A 123(2) (2017) 22. D. El Hadri, A. Zakriti, A. Zugari, M. El Ouahabi, J. El Aoufi, High isolation and ideal correlation using spatial diversity in a compact MIMO antenna for fifth-generation applications. Int. J. Antennas Propag. 2020, 1–10 (2020) 23. S.N.H. Sa’don et al., Analysis of graphene antenna properties for 5G applications. Sensors (Basel) 19(22) (2019) 24. D.A. Sehrai et al., A novel high gain wideband MIMO antenna for 5G millimeter wave applications. Electronics 9(6) (2020) 25. J. Kornprobst, K. Wang, G. Hamberger, T.F. Eibert, A mm-wave patch antenna with broad bandwidth and a wide angular range. IEEE Trans. Antennas Propag. 65(8), 4293–4298 (2017) 26. S. Iffat Naqvi et al., Integrated LTE and millimeter-wave 5G MIMO antenna system for 4G/5G wireless terminals. Sensors (Basel) 20(14) (2020) 27. M. Khalid et al., 4-port MIMO antenna with defected ground structure for 5G millimeter wave applications. Electronics 9(1) (2020) 28. S.F. Jilani, A. Alomainy, Millimetre-wave T-shaped MIMO antenna with defected ground structures for 5G cellular networks. IET Microwaves Antennas Propag. 12(5), 672–677 (2018) 29. D.E. Hadri, A. Zakriti, A. Zugari, M.E. Ouahabi, J.E. Aoufi, High isolation and ideal correlation using spatial diversity in a compact MIMO antenna for fifth-generation applications. Int. J. Antennas Propag. 2020, 1–10 (2020) 30. R. Chatuat, R. Akl, Massive MIMO systems for 5G and beyond networks-overview, recent trends, challenges, and future research direction. Sensors 10, 1–35 (2020)

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Dr. Manish Sharma received his BE in electronics and communication engineering from Mangalore University, Karnataka, India, in 2000 and MTech degree from Visvesvaraya Technological University, Karnataka, India, in 2007. He completed his PhD from the Department of Electronics Engineering, Banasthali University, Rajasthan, India, in 2017. He is currently working as Professor of Research at Chitkara University Research and Innovation Network (CURIN), Chitkara University, Punjab, India. His research interest includes computational electromagnetics, reconfigurable antennas, novel electromagnetic materials, dielectric resonator antennas, wideband/superwideband antennas, wideband/dual band/triple band microstrip antennas for wireless communication, smart and MIMO antennas systems, radio-frequency identification (RFID) antennas, antennas for healthcare, RF MEMS planar antenna on Si substrate, wireless networks, body area networks, meta surface based biosensors, designing of microstrip antennas using machine learning, and artificial network. Dr. Sharma has published more than 100 research articles in SCI/SCOPUS indexed journals and also holds two patent grants. He has guided two PhD students, and he is currently guiding eight PhD scholars.

Chapter 6

Next-Generation Optical Wireless System for 5G and Beyond Sahil Nazir Pottoo, Rakesh Goyal, Amit Gupta, and Monika Rani

6.1

Introduction

Progress in data center interconnection (DCI) technology and photonics stirred a rejuvenated curiosity in FSO techniques. The matter of electromagnetic spectrum scarcity and channel deprivation has been lately tackled by establishing FSO links gaining impressive flexibility in frequency spectrum allocation. Typical features, like ultrahigh speeds, license-free bandwidth, low-power utilization, last mile access, backhaul/fronthaul network, 4K/8K video broadcast, easy and low-cost installation, and extraordinary network security over typical wireless local area network (WLAN) distances [1, 2], earn FSO a paramount position and provide strong alternative to radio frequency (RF) technology to turn the conception of smart city, Internet of Things (IoT), and fifth-generation (5G) technology into reality. Since FSO signal propagates through the air/free-space channel, several atmospheric elements influence the quality of transmitted signal [3]. For ultrahigh speed optical wireless communication systems, spectrally efficient modulation/demodulation formats and coherent detection design combined with polarization multiplexing techniques are presently receiving substantial consideration. Multilevel quadrature amplitude modulation (QAM) encodes data on the amplitude as well as the phase of the laser beam and hence is an efficacious approach to achieve higher data rate and transmission coverage without increasing the bandwidth [3, 4]. Advanced digital signal processors (DSPs) run digital domain impairment compensation algorithms to retrieve the original transmission signal precisely [5, 6]. Bit error ratio (BER), constellation diagram, optical signal-to-noise ratio

S. N. Pottoo · R. Goyal (*) · A. Gupta Department of ECE, IK Gujral Punjab Technical University, Kapurthala, Punjab, India e-mail: [email protected] M. Rani Department of Mathematics, Kanya Maha Vidyalaya, Jalandhar, Punjab, India © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 S. Singh et al. (eds.), Broadband Connectivity in 5G and Beyond, https://doi.org/10.1007/978-3-031-06866-9_6

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(OSNR) [7], and in recent times error vector magnitude (EVM) can be used as ultimate performance indicators to measure the transmission quality in optical wireless networks [8, 9]. Researcher groups have been working to overcome the challenges in the FSO link and to enhance potential system capacity, spectral efficiency, and transmission distance using advanced optical modulation techniques [10]. M-ary QAM transceiver system provides higher data rates, but at the cost of noise margin however recently, it has been shown that employing diversity techniques in coherent FSO communication systems improve receiver SNR significantly [11, 12]. Industries prefer single-channel communication scheme since it offers essential bit rate and vigorous communication link at a minor cost [13, 14]. By employing DSP techniques, the digital signal at the output of ADC is further processed using DSP circuits for noise removal and data recovery [15]. The use of DSP in conjunction with coherent detection allows the preservation of full information of the incoming signal, which in return increases receiver sensitivity [16, 17]. By employing DSP techniques including constant modulus algorithm (CMA), it was possible to mitigate the multipath effect in a 400G fiber/wireless hybrid system combined with polarization division multiplexing (PDM) and multiple input-multiple output (MIMO) communication [3, 18, 19]. Carrier phase estimation (CPE) algorithms track and remove the phase noise using different methods such as normalized least means square estimator, differential phase estimation, and Viterbi-Viterbi (VV) estimators [20–22]. Although it is still difficult to establish a high-speed and long-haul FSO link owing to challenges put forth by climate and physical installation, coherent detection along with advanced digital modulation techniques and digital signal processing (DSP) algorithms has considerably assisted to resolve the trouble, and hence in this chapter, we implemented the 16-QAM, homodyne detection, and DSP techniques altogether in one transceiver for the best performance. This chapter presents the numerical simulation studies of a binary-driven optical square 16-QAM free-space optical communication transceiver under high-speed operation of 140 Gbps. In-phase/quadrature modulator (IQM)-based coherent optical transmission systems is designed since it provides high bandwidth efficiency and greater transmission capacity for the terrestrial, optical wireless communication systems. Further, the maximum reach of the system is analyzed based on successful reception of polarization-multiplexed (pol-mux) 16-QAM data through 5.80-km free-space distance. The overall system studies are done by powerful OptiSystem photonic software through which bit error rate (BER), error vector magnitude (EVM), optical signal-to-noise ratio (OSNR), laser linewidth, and receiver sensitivity values are noted and results have been generated using OptiSystem-MATLAB co-simulation. We report the performance enhancement using DSP techniques with various steps such as DC blocking, normalization, low-pass filter (LPF), resampling, quadrature imbalance (QI) compensation, timing recovery, adaptive equalizer (AE), frequency offset estimation (FOE), and carrier phase estimation (CPE). These postcompensation techniques have been implemented to overcome the signal transmission impairments and recover the original transmitted symbols, which allow to achieve extended FSO link range.

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For conciseness, the remainder of the chapter is structured as follows: Sect. 6.2 presents (a) transceiver block diagram, (b) theoretical and numerical investigation, and (c) transmitter, receiver, and DSP internal architectures. Section 6.3 describes simulation design and parameters and reports electrical and optical visualizer outputs. Section 6.4 discusses the results obtained from the numerical simulation. Finally, Sect. 6.5 closes the chapter with important conclusions.

6.2 6.2.1

Theoretical and Numerical Analysis Block Diagram

The block diagram of single-carrier coherent DP-16-QAM FSO transceiver using DSP displayed in Fig. 6.1 consists of optical DP-16-QAM transmitter, air/free-space channel, DP-16-QAM homodyne receiver, DSP unit, decision component, QAM sequence decoders, and parallel-to-serial (P/S) converter. The continuous wave (CW) laser beam is bisected into two quadratic polarization components (X and Y) through polarization beam splitter (PBS) which are then modulated and passed into a polarization beam combiner (PBC) at the transmitter output terminal [23, 24]. FSO channel experiences atmospheric attenuation and turbulence. Optical DP-16-QAM receiver is built over the homodyne receiver structure which provides 3-dB receiver sensitivity improvement against heterodyne detection. The detector has a local oscillator (LO) polarized at 45o with respect to PBS. Each LO component separately demodulates the received signal with two 16-QAM demodulators [25]. The DSP component carries out a number of impairment compensation algorithms to aid in recovering the incoming transmission signal after coherent detection. The decision unit normalizes the amplitudes of X- and Y-electrical signals and compares each received symbol based on normalized threshold settings. QAM sequence decoders decrypt the square 16-QAM constellation points, and the output is generated from two parallel input I/Q subsequences. In QAM modulation, the amplitude of the modulated signal can be varied according to the binary symbols.

Input Bit Stream

Optical DP-16QAM Transmitt er

FSO Channel

Optical Coherent DP-16QAM Receiver

Advanced Digital Signal Processing

QAM Sequence Decoder 1 P/S Converter

Decision Unit QAM Sequence Decoder 2

Fig. 6.1 Block diagram of the proposed next-generation optical wireless transceiver

Output Bit Stream

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The value of amplitude for each output signal is taken from the set of amplitudes given by [26, 27]: a1 ¼ ð2k  1  M Þ

ð6:1Þ

where k ¼ 1, 2, - - -, M and M is the number of possible binary sequences, which is given by [28, 29]: b

ð6:2Þ

M ¼ 22

where b represents bits for each symbol. The respective QAM set is given by the square of the term, M. This means if b ¼ 4 and M ¼ 4, then it is 16-QAM format. In order to reduce error floor, differential encoding has been implemented.

6.2.2

Optical DP-16-QAM Transmitter

Figure 6.2 demonstrates the internal structure of the optical DP-QPSK transmitter. The laser instantaneous electric field is given by [27, 30]: E L ðt Þ ¼

pffiffiffiffiffiffiffiffiffiffi PðLÞ e

jðωL tþϕL Þ

:be

ð6:3Þ

where P(L ) is laser power, ωL ¼ 2πfL is angular frequency, ϕL is initial phase, and be is signal polarization. Laser phase noise is given by the expression [31]: f ðΔϕÞ ¼

1 pffiffiffiffiffiffiffiffiffiffiffi e 2π Δf Δt



Δϕ2 4πΔf Δt



ð6:4Þ

where Δϕ is phase difference and Δt is time discretization. M-ary symbol series are produced from the input binary signal by QAM sequence generators and directly headed to M-ary pulse generators. The output from M-ary pulse generators can be written as [8, 10]: 9 8 > > = < b, 0  t < t 1 V o ðt Þ ¼ ahðt Þ þ b, t 1  t < t 1 þ w > > ; : b, t 1 þ w  t < T

ð6:5Þ

where b is parameter bias, t1 is pulse position, a is gain, w is pulse duration, T is bit duration, and h(t) is given by [7, 23]:

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Next-Generation Optical Wireless System for 5G and Beyond

Amp

107 Optical Signal Electrical Signal Binary Signal

+

M-ary Pulse Generator

LiNb MZM

Amp

+

Amp

+

M-ary QAM Sequence Generator

M-ary Pulse Generator

= 90º LiNb MZM

Amp

Input Binary Signal Serial to Parallel Converter

Modulated Optical DP-16-QAM Signal Polarization Combiner

Polarization Splitter

Amp

M-ary Pulse Generator

CW Laser

LiNb MZM

Amp

+

Amp

+

M-ary QAM Sequence Generator

M-ary Pulse Generator

= 90º LiNb MZM

Amp

+

Fig. 6.2 Internal architecture of optical DP-16-QAM transmitter

2

πt δπt3 sin cos hðt Þ ¼ 4 n T  2To 5 πt 2δt T 1 T

ð6:6Þ

where δ is the roll-off factor [17]. These multilevel samples pass through dual-drive lithium niobate Mach-Zehnder modulators (MZMs) where at peak point of operation each MZM has 30-dB extinction ratio, 3-V switching bias voltage, and 0-V bias  voltages (V1 and V2) [32, 33]. The signal is phase shifted by 90 in each quadraturephase branch of the IQM sections to generate the modulated optical 16-QAM signal. Subsequently, the X- and Y-polarization components are combined by a PBC to produce a 140-Gbps DP-16-QAM information signal at the transmitter output. This information carried over FSO channel is given by [34] [35]:

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" Prx ¼ Ptx

# Drx 2 10αZ=10 2 ðDtx þ θZ Þ

ð6:7Þ

where Prx and Ptx are receiver and transmitter optical powers, respectively; Drx and Dtx are receiver and transmitter telescope antenna diameters, respectively; θ is angle of beam divergence; Z is propagation distance; and α is specific atmospheric attenuation constant.

6.2.3

Optical DP-16-QAM Receiver

Homodyne detection-based 16-QAM receiver consists of PBS that splits the received optical signal into two output components [31, 36], two back-to-back 90-degree optical hybrids that coherently demodulate the optical carrier signal, and balanced photodetectors (BDs) which translate optical intensities into I/Q electrical signals [14, 26, 37–39]. Figure 6.3 shows the homodyne receiver structure for the 16-QAM demodulation and signal processing functions acting on the optical carrier, such as optical filtering and dispersion compensation, can be performed at the

Optical Signal Electrical Signal

PIN Subtractor

Amp

Subtractor

Amp

Subtractor

Amp

Subtractor

Amp

Ixx(t)

PIN

Optical DP-16-QAM Signal

PIN

Polarization Splitter = 90º

CW Laser

PIN

PIN

Polarization Splitter

Ixy(t)

Iyx(t)

PIN

PIN

= 90º 90 Degree Optical Hybrid Scheme

Fig. 6.3 Internal architecture of optical DP-16-QAM receiver

Iyy(t)

PIN Balanced Homodyne Detection Scheme

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electrical stage after detection [40, 41]. The output I/Q currents for the corresponding X- and Y-polarizations are expressed as [6, 42]: I I ðX=Y Þ ðt Þ ¼ I QðX=Y Þ ðt Þ ¼

pffiffiffiffiffiffiffiffiffiffiffi 2γ 1 PL Plo eL elo e2αZ fI ðt  τÞ cos ðβðωL Þd  Δϕðt ÞÞ þ Qðt  τÞ sin ðβðωl ÞZ  Δϕðt ÞÞg þ ishI pffiffiffiffiffiffiffiffiffiffiffi 2γ 1 PL Plo eL elo e2αZ fQðt  τÞ sin ðβðωL Þd  Δϕðt ÞÞ  I ðt  τÞ cos ðβðωL ÞZ  Δϕðt ÞÞg þ ishQ

ð6:8Þ ð6:9Þ

pffiffiffiffiffiffiffiffiffiffi where Pl Plo is the branch current magnitude; eL and elo are polarization components of incoming optical beam and LO signal, respectively; Δϕ(t) is phase variation; and ish is the photocurrent generated by detector shot noise.

6.2.4

Advanced Digital Signal Processing Algorithms

The DSP unit as shown in Fig. 6.4 carries off several digital domain impairment compensation techniques to assist in recovering the original transmitted bit stream after coherent detection of optical square 16-QAM modulated signal. It has been used with optical coherent receiver that utilizes 16-QAM modulation with dual polarization (X and Y channel) multiplexing. The high-level DSP module works by employing nine algorithms starting with a two-step preprocessing stage, (1) DC blocking and (2) normalization, followed by the seven-step signal recovery stage: (3) low-pass Bessel filter, (4) resampling, (5) quadrature imbalance (QI) compensation, (6) timing recovery, (7) adaptive equalizer (AE), (8) frequency offset estimation (FOE), and (9) carrier phase estimation (CPE). Figure 6.9 in Sect. 6.4 shows the constellation diagrams obtained for each of the various signal

After Filtering

Qy

QI COMPENSATION

Iy

RESAMPLING

Qx

BESSEL FILTER

Ix

After Frequency Offset Estimation

After Adaptive Equalizer

After QI Compensation

After Resampling

After Carrier Phase Estimation

hxx hxy

FOE

CPE

hyx

FOE

CPE

hyy EQUALIZER

Fig. 6.4 Internal architecture of digital signal processor

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impairment compensation stages of the DSP unit after 5.8-km FSO transmission. The DSP unit recovers the original transmitted symbols from the received electrical signals by the application of various high-level algorithms at each signal processing stage.

6.3

Transceiver Design and Simulation Parameters

The single-channel optical wireless communication system shown in Fig. 6.5 is designed using OptiSystem V.16 simulation platform. Table 6.1 summarizes various simulation parameters with their values. The principle of operation of the transmitter, receiver, and DSP unit has been covered in Sects. 6.2.2, 6.2.3, and 6.2.4, respectively. Numerous electrical and optical visualizer components such as optical spectrum analyzer (OSA), optical time domain visualizer (OTDV), electrical constellation visualizer, RF spectrum analyzer, eye diagram analyzer, and BER test set have been included in the simulation model to note and evaluate the performance of the proposed transceiver at various instants. Figure 6.6 displays OSA and RF spectrum analyzer outputs. Figure 6.6a shows the optical spectrum of the 140-Gbps DP-16-QAM signal at the transmitter output. The center frequency is at 193.414 THz (i.e., 1550 nm), and the peak power observed at this frequency is –16.7394 dBm. Figure 6.6b shows the RF spectrum of the 140-Gbps DP-16-QAM electrical signal at the output of coherent receiver. The center frequency is at 1.6 THz (i.e., 1874 nm), and the power observed at this frequency is –100 dBm. Figure 6.7 illustrates eye diagrams of the modulated DP-16-QAM signal at 5.8km FSO transmission distance. Figure 6.7a denotes eye diagram of 16-QAM

Fig. 6.5 Transceiver model designed using OptiSystem V.16 photonic software

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Next-Generation Optical Wireless System for 5G and Beyond

Table 6.1 Design parameters and corresponding values

Parameters Bit rate Frequency Transmitted power Linewidth Initial phase Baud rate Beam divergence Transmitter aperture diameter Receiver aperture diameter Receiver loss Responsivity Dark current Transmission range Photodetector type Atmospheric attenuation Geometrical loss Sequence length

111 Values 140 Gbps 193.414 THz 20 dBm 0.1 MHz 0 degree 40 Gbaud 0.25 mrad 5 cm 20 cm 1 dB 1 A/W 10 nA 5.8 km PIN 0.25 dB/km Yes 65,536

Fig. 6.6 (a) Optical spectrum of the DP-16-QAM signal at the transmitter output, and (b) RF spectrum of DP-16-QAM signal after the homodyne detection

in-phase signal, while Fig. 6.7b shows eye diagram of 16-QAM quadrature-phase signal. It can be noticed that both eye diagrams validate successful transmission of 140-Gbps DP-16-QAM information signal up to a maximum reach of 5.8 km under

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In-quadrature signal - Q 1

0

2

0

0

–2

–2

Amplitude (a.u.)

2

0

0.5 Time (bit period)

(a)

1

0.5

1

2

2

0

0

–2

–2

Amplitude (a.u.)

0

0

0.5 Time (bit period)

1

(b)

Fig. 6.7 (a) Eye diagram of 16-QAM in-phase signal, and (b) eye diagram of 16-QAM quadraturephase signal at 5.8-km FSO distance

Fig. 6.8 (a) Optical input timing phase, and (b) optical output timing phase, at the DP-16-QAM transmitter output

fair weather within acceptable performance margin using the proposed system. Figure 6.8a, b denote input timing phase and output timing phase, respectively, at the DP-16-QAM transmitter output measured using OTDV.

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6.4

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Results and Discussion

This segment discusses the outcomes obtained from the simulative investigation of the proposed FSO transceiver. Firstly, we report the constellation diagrams of demodulated signal acquired after passing through each algorithm of the ninestage DSP unit. Secondly, we examine the proposed QAM-FSO link utilizing BER, EVM (%), OSNR, laser linewidth, received optical power, and transmission distance as performance parameters. Constellation diagrams at different stages of the proposed DP-16-QAM-based FSO link using DSP are reported in Fig. 6.9. Figure 6.10 displays BER performance of the proposed system in fair weather conditions. For a range of 0–10 km, different values of BER are computed. As follows from the graph, BER of the information signal increases with increasing link distance. The result demonstrates successful transmission of 140-Gbps data bearing DP-16-QAM optical signal up to a distance of 5.80 km under acceptable performance criteria, that is, BER 2  103 (FEC limit). However, with the increase in the distance, distortion in the scattering diagram increases, due to which information retrieval becomes harsh on receiver terminal. This performance deterioration is triggered by linear distortions, geometric loss, misalignment loss, free-space loss, atmospheric turbulence-induced fading, ambient noise, laser phase noise, and OSNR degradation, respectively. Figure 6.11 shows the receiver sensitivity, i.e., BER and EVM (%), versus received optical power graphs of the proposed FSO link. The system performance has been evaluated at the maximum transmission distance of 5.80 km. The received optical power is varied with the help of optical attenuator at the receiver input, and the corresponding EVM (%) and BER are found out. Figure 6.12 shows the BER and EVM (%) performance of 140-Gbps DP-16QAM system for different laser linewidths after 5.80-km FSO transmission. It is observed that both the EVM and BER degrade with increasing laser linewidths because at greater linewidths, the optical spectrum of the modulated signal gets broader, and it contributes to frequency dispersion in the optical signal while propagating. Narrow laser linewidth is key to high-performance homodyne detector. Figures 6.13 and 6.14 demonstrate performance of BER with OSNR and EVM with OSNR, respectively. It is observed that with increasing values of OSNR, log (BER) and EVM (%) value decreases. Hence, with greater values of OSNR, constellation points become more discrete. It is noted that for higher values of OSNR, the system is less prone to error. In communication systems, random noise cause erroneous bits, the occurrence of which is measured as BER. OSNR is a vital parameter since it quantifies the degree of impairment when the modulated laser signal is carried through free space. The OSNR requirement of the optical wireless network is analytical since it reduces working expenditure and boosts the bit rate of the network. EVM (%) is an appropriate metric for the evaluation of coherent communication systems with higher-order modulation formats. The mathematical expressions used for the calculation of BER, OSNR, and EVM (%) are as follows: BER for dual polarization system is given by [43, 44]:

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Fig. 6.9 Constellation diagrams for 140-Gbps-5.80-km FSO link (a) at the DP-16-QAM transmitter, (b) before DSP, i.e., after the coherent detection, (c) after DC blocking, (d) after normalization, (e) after low-pass filter, (f) after resampling, (g) after quadrature imbalance compensation, (h) after timing recovery, (i) after adaption equalizer, (j) after frequency offset estimation, (k) after carrier phase estimation over clear climate

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Fig. 6.9 (continued)

115

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Fig. 6.9 (continued)

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117

Fig. 6.9 (continued)

BER ¼

X errors þ Y errors sequence length  ð2  guard bitsÞ

ð6:10Þ

where only those errors are add up which lie outside the portion of the sequence of the guard bits. BER for the X-polarization channel is given by [45, 46]: BERx ¼

X errors ðsequence length  2  guard bitsÞ=2

BER for the Y-polarization channel is given by [47, 48]:

ð6:11Þ

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Fig. 6.10 log(BER) versus link length graph under fair climate (insets: corresponding constellation plots)

Fig. 6.11 BER and EVM (%) versus received optical power of the proposed link at 5.80-km FSO link with 0.25-dB/km atmospheric attenuation

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119

Fig. 6.12 BER and EVM (%) versus laser linewidth plot of the proposed system at 5.80-km FSO link reach

Fig. 6.13 BER and EVM (%) versus OSNR plot of the 140-Gbps QAM/FSO system at 5.80 km FSO link under clear weather condition.

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Fig. 6.14 EVM (%) versus OSNR plot of the proposed QAM/FSO link

BERy ¼

Y errors ðsequence length  2  guard bitsÞ=2

ð6:12Þ

In order to add a definite noise level to transmitted optical signal, set OSNR unit is used. The OSNR level is set based on the following equation [33, 49]:  OSNRðdBÞ ¼ 10 log 10

 Ps ðmWÞ ¼ ½dBðsignalÞ  dBðnoiseÞ Pn0:1 ðmWÞ

ð6:13Þ

where Ps is the total signal power within the signal bandwidth (2  symbol rate) and Pn0.1 is the noise power measured within a 0.1-nm bandwidth window. As the noise is added to the signal using a power combiner, there is a 3-dB transmission loss applied to both the signal and noise source, but the OSNR level is not affected. To achieve BER value under forward error correction (FEC) limit [28], that is, 2  103, the least necessary OSNR value denotes the noise acceptance of a modulation format over 0.1 nm of finite bandwidth. The relation between BER and OSNR is given by [50, 51]:

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Next-Generation Optical Wireless System for 5G and Beyond

hpffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffii 3 BER ¼ erfc OSNRNL =2 8

121

ð6:14Þ

The EVM (%) and BER relation is of noteworthy importance for coherent optical transmission systems [52], since EVM (%) is well-matched than BER measurement for indefinite symbol sequences and to distinguish optical I/Q transmitters. EVM is described as the root-mean-square (RMS) value of the deviation among calculated constellation points and ideal constellation points. EVM is measured with vector signal analyzers directly from down-converted signals [53]; as a result, additional computation is reduced that may be needed to figure out the BER. The EVM of the received signals is calculated as follows [54–56]:

EVM ¼

qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi    S  bSc  2 u bSc2u

 100%

ð6:15Þ

 2 where symbol sequence is denoted by S, mean value is written as S  bScu  , and bScu represents the decision of S, respectively. RMS value of EVM is given by [34, 57]:

EVMrms

sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 2ffi P  1=N Nj¼1 E r,j  Et,j  ¼ Pa

ð6:16Þ

We can relate BER with EVM by [58, 59]: sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi  1  M 1=2 3=2 erfc BER ¼ 1=2 log 2 M ðM  1ÞEV M 2rms 

6.5

ð6:17Þ

Conclusions

We report a nine-stage DSP method with homodyne detection for high-capacity long-haul coherent polarization-multiplexed (pol-mux) systems using 16-QAM. In the first stage, a two-step preprocessing using DC blocking and normalization is implemented, followed by the seven-step signal recovery algorithms in the second stage. A blind adaptation technique-based butterfly equalizer is used to demultiplex PDM signals with significant out-of-band cross talk and also compensate linear distortions well. The joint implementation of coherent detection and DSP demonstrate numerous advantages including better steady-state performance and a faster convergence rate. Furthermore, all the estimation and equalization algorithms are implemented in the frequency domain which potentially provides the least

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complexity for the pol-mux optical coherent systems. The proposed algorithms are simulatively demonstrated with a 5.80-km 40-Gbaud coherent optical pol-mux system under the presence of additive white Gaussian noise, which established high-quality symbol constellation and a BER performance similar to theoretical expectations. For QAM signal, the proposed method achieves error-free transmission and shows superior coverage and speed and hence outperforms the traditional intensity modulation/direct detection (IM/DD) system.

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Sahil Nazir Pottoo is pursuing his PhD in electrical engineering with the main focus on optics and photonics from UiT The Arctic University of Norway. He received the MTech in wireless communications in 2020 from the I. K. Gujral Punjab Technical University, India, with the first rank in the batch (gold medalist). He received BTech in electronics and communication engineering in 2018 from the Baba Ghulam Shah Badshah University, India. His master’s thesis involved primary research on the design and numerical simulations of coherent free-space optical communication transceivers for 5G/6G applications. He has published his research findings in various SCI journals and IEEE international conferences. He is acting as the technical reviewer for SPIE journals – Optical Engineering, the Journal of Optical Communications, the Journal of Computer Science, and the Journal of Optics, and he is an accredited reviewer of the Optica (OSA). His research interests are free-space optics, deep learning, and photonics. Dr. Rakesh Goyal is working as an assistant professor in the Electronics & Communication Engineering Department, IK Gujral Punjab Technical University, Kapurthala, Punjab. He has completed his PhD and MTech in electronics and communication engineering from Thapar University, Patiala, Punjab, and BTech in electronics and communication engineering from Kurukshetra University, Kurukshetra. He has also qualified GATE 2007. Dr. Goyal has 12 years of teaching experience. He has more than 100 publications including books, SCI/ Scopus journals, and international and national conferences. He is also a reviewer for reputed international journal publishers including IEEE, IET, Springer Nature, Elsevier, Taylor and Francis, Degruyter, and Optical Society of America.

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Amit Gupta obtained his BTech from Kurukshetra University, Kurukshetra (Haryana), India. He received his master’s and doctorate degrees from Punjab Technical University, Jalandhar (Punjab), India, in electronics and communication engineering. Has more than 18 years of teaching experience and has guided many research scholars at master’s and PhD level. He also has more than 80 publications to his credit in reputed SCI/SCOPUS journals and various conferences. His area of research includes optical wireless communication systems. Dr. Monika Rani is working as an assistant professor in PG Department of Mathematics, Kanya Maha Vidyalaya, Jalandhar, Punjab, since 2016. She has total 11 years of teaching experience. She has completed her PhD from I K Gujral Punjab Technical University, Kapurthala, Punjab, India. She has done her MSc in mathematics from Kurukshetra University Kurukshetra, Haryana. She has also qualified CSIR-UGC-NET 2013 and 2015, GATE 2013, and HTET 2013. Her area of interest is number theory and differential equations. She has more than 80 publications in international journals and conference proceedings. She has also been awarded a gold medal and elite certificate by the Indian Institute of Technology (IIT) Kanpur in NPTEL course in 2019. She has been awarded a merit certificate by the Board of School Education Haryana in 1997 and in 1999.

Chapter 7

Performance Evaluation of 80-Gbps TWDM-Based NG-PON2 for Various Network Topologies Ramandeep Kaur, Simranjit Singh Tiwana, and Rajandeep Singh

7.1

Introduction

The demand for data rate growth is increasing day by day at the global level. To fulfill the demands, advanced network architectures and different data transfer technologies are required. The fiber-to-the-home (FTTH) technology is being widely deployed all over the world [1]. For the last-mile network, a passive optical network (PON) is a modern high-speed access solution that provides broadcast high data rate to the end users. Moreover, PON can also be deployed with existing metallic cables to create different FTTx (x means curb, building, home, etc.) solutions. The optical distribution network (ODN) in the PON access network consists of all passive components like optical power splitters, optical fiber, couplers, etc. The nextgeneration passive optical network stage 2 (NG-PON2) is a long-term solution in PON evolution. According to the standards, NG-PON2 technology should outperform existing PON technologies in terms of ODN compatibility, bandwidth, capacity, and cost-efficiency [2, 3]. As per the G.989.2 recommendation of ITU-T, the best hybrid-multiplexed technique for NG-PON2 is time and wavelength division passive optical network (TWDM-PON). TWDM utilizes the bandwidth of optical fiber efficiently [4]. The NG-PON2 is a broadcast network, and a large number of optical network units (ONUs) can be served using various network topologies. The NG-PON2 network can be configured with topologies like bus, tree, and star topology. These topologies are arrangement or mapping of the links, nodes, etc. of a network [5, 6]. For a particular application, one topology can be more suitable than others. Also, every topology has advantages and disadvantages.

R. Kaur (*) · S. S. Tiwana Department of ECE, Punjabi University, Patiala, Punjab, India R. Singh Department of Electronics Technology, GNDU Amritsar, Amritsar, Punjab, India e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 S. Singh et al. (eds.), Broadband Connectivity in 5G and Beyond, https://doi.org/10.1007/978-3-031-06866-9_7

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In any passive optical link, modulation formats play an important role for better system performance. S.M. Idrus et al. investigated the performance of the 25-Gbps NG-PON system experimentally with a 25-km reach by employing a dual phaseshift keying (DPSK) signal at downstream transmission and its conversion to optical duobinary modulation format at the ONU receiver. The receiver sensitivity of 29 dBm was observed for bit error rate (BER) less than 10 5 with a 1:64 split ratio [7]. A low-cost 40-Gbps TWDM PON was investigated by Bart Moeneclaey et al. using electrical duobinary modulation (EDM) format at the downstream transmission. They achieved a power budget of 23.6 dB with forward error correction (FEC) and BER level of 10 3 with 20-km system reach [8]. The system performance was investigated by employing different optical network topologies in the presence of a hybrid optical amplifier by Sanjeev Dewra et al. They reported that bus topology supports 18 nodes for a minimum signal input power of 20 dBm and ring topology supports 30 nodes for 30-dBm input power at 10-Gbps data rate with 30-km reach between successive nodes in the presence of hybrid amplifier. However, in hybrid topology, they found that the number of nodes supported for bus topology is 6 and for the ring it is 10 at 20-dBm signal input power [9]. To increase the resilience of the WDM-PON network, the ring topology was implemented at the remote node (RN) using a standard optical splitter of 1:2 split ratio by P. Lafata et al. To verify the experimental results, they measured and compared the results with the simulation model [10]. Chung-Yi Li et al. proposed a novel tree-based optical add/drop multiplexer (TOADM) for TWDM NG-PON2. They used two four-port optical circulators (OCs), one three-port OC, and two fiber Bragg grating (FBGs) passive components to place at any selected location along with transmission fiber to multiplex and demultiplex optical wavelengths. They observed the results through an experiment that the insertion losses of the proposed device are less than a 1  2 optical splitters in downstream and upstream directions [11]. From the above literature review, it is observed that network topologies are playing an important role in the broadcast access network and the work is limited to low data rate and a smaller number of users served by the system. To overcome these limitations and for the future proof solution, the NG-PON2 network comes into play. NG-PON2 network is capable to extend the network capacity to 40 Gbps or to 80 Gbps by employing multiple optical carriers [12]. In this chapter, the performance of different topologies like bus, star, and tree topology has been analyzed in TWDM-based symmetric 80-Gbps NG-PON2 with 1024 users. The system is also investigated for the avalanche photodiode (APD) and PIN photodiode. This chapter is organized into four sections. Introduction is given in the first section. In the second section, the simulation setup for bus topology and the RN design using array waveguide grating (AWG) are presented, and simulated results are discussed. Section 7.3 presents the simulation architecture of star topology and its simulated results. The simulation setup and results for tree topology are presented in Sect. 7.4. The conclusion is made in the last section.

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7.2

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Simulation Architecture of 80-Gbps NG-PON2 with Bus Topology

In system architecture for bus topology in NG-PON2, all eight wavelengths starting from 1596 nm with 0.8-nm channel spacing are multiplexed at the central office (CO)/optical line terminal (OLT) as shown in Fig. 7.1. Each wavelength carries a 10-Gbps data rate which makes the system capable of 80-Gbps data rate service. The multiplexed data is transmitted over single-mode fiber (SMF). Near the user premises, the data is broadcasted using a bus topology. In this topology, all ONUs are connected to a shared transmission fiber. The data is transmitted in the network to the dedicated groups of ONUs as per the assigned wavelengths. In this way, the data is transmitted between every ONU and OLT over the same main fiber.

7.2.1

RN Design Using AWG for 80-Gbps TWDM-Based NG-PON2 Downstream with Bus Topology

Eight wavelengths for downstream transmission are used in this work. So, each RN is allocated with a fixed downstream wavelength. The generalized node structure of nth is presented to explain how downstream and upstream wavelengths pass through the node, where n represents 1, 2, 3, 4, 5, 6, 7, and 8. Overall, there are eight RNs in the network. Figure 7.2 shows the block diagram of the nth RN for AWG-based bus topology.

Fig. 7.1 Simulation architecture of 80-Gbps NG-PON2 with bus topology

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Fig. 7.2 Design of nth remote node using AWG for bus topology

The wavelengths λn λ8 enter the nth RN from the left branch of node for downstream transmission. Out of λn λ8, the wavelength λn is dropped by AWG1 and is sent to 128 ONUs through power splitter. After dropping λn, all the remaining downstream wavelengths λn+1 to λ8 are multiplexed by AWG2 and are sent to the remaining remote nodes. Simultaneously, the ONUs of nth RN transmit upstream data using wavelength λn+8 toward the OLT using the TDM technique. As shown in Fig. 7.2, all ONUs operating at nodes RNn+1 to RN8 generate upstream traffic on the wavelengths λn+9 to λ16; these wavelengths enter RNn from the right side of the nth node. In the nth RN, the upstream generated on λn+8 gets combined with λn+9 to λ16. Therefore, the nth RN sends upstream on λn+8 to λ16 wavelengths toward OLT. The circulator provides a path to the upstream wavelengths which are incoming from the right side of the nth node.

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The upstream wavelength of the ONUs operating on nth RN is λn+8 whose power is combined with the upstream wavelengths entering the nth RN, i.e., λn+9 to λ16. Therefore, the λn+8 to λ16 contains upstream data of all ONUs working on RNn to RN8, and these wavelengths are propagated toward the RNn 1, which further adds one more upstream wavelength. Ultimately, the upstream data of all 1024 ONUs working in the entire systems reaches the OLT. This way, the proposed RN design can drop a single wavelength designated to that particular RN without affecting others. Also, the node can add the upstream traffic generated by ONUs connected to that particular node. The presented RN design is entirely passive, making this upand-coming candidate since the active components are not desirable in PON.

7.2.2

Results and Discussion

The performance of bus topology-based 80-Gbps NG-PON2 is investigated by observing the acceptable BER for minimum received power in case of ONUs working at first, fifth, and eighth wavelengths. These graphs are shown in Figs. 7.3, 7.4, and 7.5.

Fig. 7.3 BER vs received power at RN1 for downstream transmission

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Fig. 7.4 BER vs received power at RN5 for downstream transmission

Figure 7.3 shows the graphical representation of the BER variation for varied received power for the ONU operating at the RN1. The acceptable BER (