Optical Wireless Communications System and Channel Modelling with MATLAB
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Optical Wireless Communications System and Channel Modelling with MATLAB

Optical Wireless Communications System and Channel Modelling with MATLAB  2nd Edition by Z. Ghassemlooy, W. Popoola, and S. Rajbhandari | PDF Free Download.

Authors of Optical Wireless Communications System and Channel Modelling

Professor Zabih Ghassemlooy

Ghassemlooy, CEng, Fellow of IET, Senior Member of IEEE and OSA received his BSc (Hons.) in electrical and electronics engineering from Manchester Metropolitan University, UK, in 1981, and his MSc (1984) and Ph.D. (1987) from the University of Manchester, UK. From 1987 to 1988, he was a Post-Doctoral Research Fellow at City University, UK.

In 1988, he joined Sheffield Hallam University as a lecturer, becoming a professor in 1997. In 2004, he joined the University of Northumbria, Newcastle, as an associate dean (AD) for research in the School of Engineering, and from 2012 to 2014 he was AD for Research and Innovation, Faculty of Engineering and Environment.

He currently is head of the Optical Communications Research Group. In 2001, he was awarded the Tan Chin Tuan Fellowship in Engineering from Nanyang Technological University, Singapore.

In 2016, he was a research fellow and in 2015 a distinguished professor at the Chinese Academy of Science, Quanzhou, China. He became a visiting professor at the University Tun Hussein Onn, Malaysia (2013–2017), and Huaqiao University, China (2017–2018).

He has published over 785 papers (309 journals and six books), given more than 92 keynote/invited talks, and supervised over 60 PhDs.

His research interests include optical wireless communications, free-space optics, visible light communications, radio-over-fiber/free-space optics, and sensor networks with project funding from the EU, UK Research Council, and industry.

He was the vice-chair of EU Cost Action IC1101 (2011–2016). He is the chief editor of the British Journal of Applied Science and Technology and the International Journal of Optics and Applications, associate editor of a number of international journals, and co-guest editor of a number of special issues.

He is a fellow of the IET, a senior member of IEEE, a senior member of OSA, and a chartered engineer. He is a co-editor of four books, including Optical Wireless Communications An Emerging Technology (Springer, 2016), Visible Light Communications:

Theory and Applications (CRC, 2017), Intelligent Systems for Optical Networks Design: Advancing Techniques (IGI Global, 2013), and Analogue Optical Fibre Communications, IEE Telecommunication series 32 (IET, 1995).

He is the founder and chair/co-chair of a number of international events, including the IEEE/IET International Symposium on Communications Systems, Networks and DSP, West Asian Colloquium on Optical Wireless Communications, and Workshop on Optical Wireless Communications in ICC since 2015.

Dr. Wasiu O. Popoola

Popoola holds a first-class (Hons.) degree in electronics and electrical engineering from Obafemi Awolowo University, Nigeria, and an MSc and a Ph.D. degree, both from Northumbria University in Newcastle upon Tyne, UK. During his Ph.D. studies, he was awarded the Xcel Best Engineering and Technology Student of the year 2009.

He is currently a Chancellor’s Fellow in the Institute for Digital Communications and LiFi R & D Centre, School of Engineering at the University of Edinburgh, UK.

He has published over 100 journal articles, conference papers, and patents, more than seven of which are invited papers.

One of his journal articles ranked number 2 in terms of the number of full-text downloads within IEEE Xplore in 2008 from the hundreds of papers published by IET Optoelectronics since 1980. Another paper he co-authored with one of his Ph.D. students won the best poster award at the 2016 IEEE ICSAE Conference.

He also co-authored the book Optical Wireless Communications: System and Channel Modelling with MATLAB, published by CRC in 2012 and several other book chapters (one with over 10,000 downloads as of September 2014 since its publication in 2010).

Popoola is a senior member of the IEEE, an associate editor of the IEEE Access Journal, guest editor for Elsevier Journal of Optik (special issue on optical wireless communications) in 2017, and a technical program committee member for several conferences.

Dr. Sujan Rajbhandari

Rajbhandari (SMIEEE) is a senior lecturer at Coventry University, where he is working in the field of optical wireless communication.

Dr. S. Rajbhandari obtained an MSc in Optoelectronics and Communication Systems with Distinction in 2006 and was awarded the P. O. Byrne prize for the most innovative project.

He then joined the Optical Communications Research Lab (OCRG) at Northumbria University as a Ph.D. candidate and was awarded a Ph.D. in 2010.

He was with the OCRG at Northumbria University, working as a senior research assistant and research fellow from 2009 until 2012.

He joined the communications research group at the University of Oxford in 2012 and worked in the EPSRC’s prestigious Ultra-Parallel Visible Light Communications (UP-VLC) project, which was a collaboration of five of the UK’s leading universities (Oxford, Cambridge, St. Andrews, Edinburgh, and Strathclyde).

In 2015, Dr. Rajbhandari joined Coventry University as a lecturer in electrical and electronic engineering and was promoted to senior lecturer in 2017.

Dr. Rajbhandari is an active researcher with an international reputation as a leading expert in the field of optical wireless communication.

He has published more than 150 scholarly articles with over 3000 citations in the area of optical wireless communications, visible light communication, signal processing, and artificial intelligence, including the book Optical Wireless Communications: System and Channel Modelling with MATLAB.

His work is highly recognized nationally and internationally. Dr. Rajbhandari was the invited tutorial presenter at the 16th International Symposium on the Science and Technology of Lighting, invited speaker ICTF2015, Manchester Metropolitan University.

He is the lead guest editor for MDPI Sensors Journal special issue on Visible Light Communication Networks and guest editor for MDPI photonics special issue on Photonic Communications Systems in Access Networks and academic editor for Wireless Communications and Mobile Computing.

Dr. Rajbhandari is a co-recipient of the 2015 Winners of the IET Premium (Best Paper) Awards for Optoelectronics Journal, co-author of invited papers in Photonics Research Journal (2013), author of invited papers in CNSDSP2016, SPIE Optics 2014.

He has served as a reviewer for EPSRC grants and journals published by IEEE, OSA, IET, Elsevier, IOP, and international conferences, such as IEEE ICC 2017 and CSNDSP2016.

He has also acted as proceedings co-editor and local organizing committee member of NOC/OC&I 2011 and EFEA2012.

His research interests lie in the area of optical communication, visible light communication, optical wireless communications, signal processing, modulation techniques, equalization, applied artificial intelligence, and wavelet transform. He is a senior member of IEEE and an associate member of the Institute of Physics.

Optical Wireless Communications Contents

  • Chapter 1 Introduction: Optical Wireless Communication Systems 
  • Chapter 2 Optical Sources and Detectors 
  • Chapter 3 Channel Modelling 
  • Chapter 4 Modulation Techniques 
  • Chapter 5 Indoor System Performance Analysis
  • Chapter 6 FSO Link Performance with Atmospheric Turbulence
  • Chapter 7 Outdoor OWC Links with Diversity Techniques 
  • Chapter 8 Visible Light Communications 
  • Chapter 9 Relay-Assisted FSO Communications

Preface to Optical Wireless Communications System and Channel Modelling

In recent years, we have been witnessing a growing demand by users for bandwidth to support broadband wireless services, such as high-definition TV, mobile video phones, video conferencing, and high-speed internet access.

With the widespread use of smart devices, as well as the rapid growth in the next generation of internet-of-things (IoT) applications, the quest for sufficient bandwidth is rapidly growing.

In the access networks (i.e., last meter and last mile), there are a number of technologies that can address end-users’ communications needs, including copper wire, hybrid coaxial, and optical fiber cables, fiber-to-the-home, and a range of radiofrequency (RF)-based wireless communications.

However, as the global demand for bandwidth continues to accelerate, it is becoming exceedingly clear that copper/coaxial cables and RF cellular/microwave technologies cannot meet the upcoming needs because of their limited bandwidth, highly regulated and congested spectrum, and limited accessibility to all.

In addition, these technologies require costly licensing fees, suffer from security issues, and incur a high cost of installation. In some countries, the network operators have been deploying new optical fiber-based access networks in order to increase the bandwidth available to their customers.

Although it is often thought that optical fiber-based networks offer unlimited bandwidth, in reality, the architectural choices available, compatibility of devices and components, performance constraints of networking equipment, and deployment of the complete system result in limited capacity being offered to end-users.

Meanwhile, with regard to ubiquitous connectivity between the people and devices at a global level, we have seen a remarkable development in wireless communications technology, which can be naturally extended to provide communications between heterogeneous objects, thus enabling the widespread implementation of IoT (i.e., people-to-people, machine-to-machine, terminal-to-terminal, and people-to-machine communications).

However, using RF-based wireless technologies, we have (i) spectrum congestion, mostly evident in urban areas, which will lead to limited access to the network; (ii) multipath-induced fading and dispersion, which will affect link performance, especially in highly dense areas

And (iii) insufficient bandwidth for the efficient operation of heterogeneous devices in indoor environments, considering that more 70% of the wireless data traffic generated is indoor. To reduce the pressure on the RF spectrum, some mobile data traffic can be off-loaded to wireless fidelity (Wi-Fi) and femtocell-based technologies.

However, dense deployment of Wi-Fi hotspots is also facing the bandwidth bottleneck. Therefore, to ensure seamless wireless communication with high data rates and low latency, the service provided will have to adopt highly reliable, low-cost, and high-speed technologies.

The emerging fifth-generation (5G) and beyond-5G RF-based wireless technologies are expected to address these issues in the coming years.

However, in 5G and beyond-5G wireless networks, there will be additional challenges, such as inter-cell/inter-tier interference, management of spectral resources reuse, etc.

Alternatively, optical wireless communications (OWC), which is an innovative complementary technology to the RF wireless systems and has been around for the last three decades, can be adapted to provide high capacity with reduced latency and at a low cost in certain indoor and outdoor applications.

It offers flexible and scalable wireless networking solutions that are cost-effective, high security at the physical layer, high-speed, license-free, low power usage, immune to RF-based electromagnetic interference

And unconstrained frequency reuse due to a high degree of spatial confinement and ease of deployment for a number of applications, including voice and data, video and entertainment, enterprise connectivity, remote sensing, medical and manufacturing, disaster recovery, illumination and data communications, surveillance, localization, and many others.

In OWC technology, three bands of ultraviolet (UV), visible light (VL), and infrared (IR) can be used to provide high bandwidth for communication purposes.

Due to the unique properties of the optical signal, in an indoor environment, one can precisely define an optical footprint and hence can accommodate a number of devices within a small area.

Thus, optical wireless communications also referred to as free-space optical communication systems for outdoor applications, will play a significant role as a complementary technology to the RF systems in future information superhighways, as well as being able to comply with the 5G Infrastructure Public-Private Partnership identified key performance indicators.

Having seen the development of OWC systems in the last two decades, we felt there was a need for the second edition of this textbook with additional materials on the technology that was concise and suitable for undergraduate and graduate-level courses, as well as researchers and professional engineers working in the field.

This book broadly covers five important aspects of OWC systems: (a) the fundamental principles of OWC; (b) devices and systems; (c) modulation techniques; (d) channel models and system performance analysis; and (e) free-space optics and visible light communications. In addition, the book covers different challenges encountered in OWC, as well as outlining possible solutions and current research trends.

The major attractions of this book are (i) the Matlab simulations and the inclusion of Matlab codes and (ii) experimental testbeds to help readers understand the concepts and enable them to carry out extensive simulations, implement OWC links, and evaluate their performance.

The book is structured into nine self-contained chapters. To facilitate a logical progression of materials presented and to enable readers to better understand the topics and follow them through, each chapter starts with an introduction followed by background information supported by detailed theoretical analysis, as well as up-to-date supporting references.

Any additional supporting materials are included in the end-of-chapter appendices. Starting with a bit of history, Chapter 1 presents an up-to-date review of OWC systems for indoor and outdoor applications, the present state of play, and the future directions for the emerging OWC technology.

The wireless access technologies, benefits and limitations, link configurations, eye safety, application areas, and challenges of OWC systems are all covered in Chapter 1. There are a number of light sources and photodetectors (PIN and/or avalanche photodiodes) that could be used for OWC systems.

Light-emitting diodes (LEDs) and low-power laser diodes are mainly employed in short-range indoor applications. For long-range outdoor applications, laser diodes are mostly used.

Chapter 2 discusses the types of light sources and optical detectors, their structures, and optical characteristics, as well as the process of optical detection.

Different types of noise encountered in optical detection and the statistics of the optical detection process are also discussed in Chapter 2. To design efficient optical communication systems, it is imperative that the characteristics of the channel are well understood.

Characterization of a communication channel is performed by its channel impulse response, which is then used to analyze and proffer solutions to the effects of channel distortions.

A number of propagation models (ceiling bounce, Hayasaka-Ito, and spherical) for a line-of-sight and non-line-of-sight indoor applications are studied in Chapter 3. The artificial light interference that affects the indoor OWC link performance is also outlined in this chapter.

As for the outdoor free-space optics (FSO) links, the atmospheric channel is a very complex and dynamic environment, which can affect the characteristics of the propagating optical beam, thus resulting in optical losses and turbulence-induced amplitude and phase fluctuations.

There are a number of models to characterize the statistical nature of the atmospheric channel, mostly fog and turbulence, which are treated in Chapter 3. A practical testbed for investigating the atmospheric effect on the FSO link, measured data sets

And calibration of the indoor data to the outdoor links is also presented in Chapter 3. Most practical OWC systems currently in use are based on the intensity modulation/direct detection scheme.

For the outdoor environment, atmospheric conditions, in particular heavy fog, are the major problem, as the intensity of the light beam reduces considerably under thick fog. Increasing the level of the transmitted power is one option to improve the link availability.

However, eye safety regulations limit the amount of transmitted optical power. For indoor applications, the eye safety limit on transmitted optical power is even more stringent.

In Chapter 4, a number of modulation techniques, which are the most popular, in terms of power efficiency, bandwidth efficiency, for both indoor and outdoor OWC applications are discussed.

The emphasis is more on the digital modulation techniques including pulse position modulation (PPM), on-off keying (OOK), digital pulse interval modulation (DPIM), etc.

The spectral properties, error probability, and the power and bandwidth requirements of a number of modulation schemes are also presented.

Advanced modulation techniques, such as the subcarrier intensity modulation, and multi-carrier modulations, such as orthogonal frequency division multiplexing, carrier-less amplitude, and phase modulation, and polarisation shift keying, are also covered in this chapter.

In indoor scenarios, additional periodic and deterministic forms of noise that degrades system performance is due to the presence of background artificial light sources.

The diffuse indoor links suffer from the multipath-induced intersymbol interference, thus limiting the maximum achievable data rates. The performance of the OOK-, PPM-, and DPIM-based systems in the presence of artificial light interference and intersymbol interference is investigated in Chapter 5.

To improve the link performance, possible mitigation techniques using high-pass filtering, equalization, wavelet transform, and the neural network are also outlined in this chapter. Atmospheric turbulence is known to cause signal fading in the channel.

Chapter 6 outlines the outdoor FSO link performance in terms of the bit error rate and the outage probability under atmospheric turbulence for a range of modulation schemes of OOK, PPM, PSK, QPSK, DPSK, etc.

A range of channel models is also considered. Primary challenges attributed to outdoor OWC (i.e., FSO) communications are building sway, scattering/absorption-induced attenuation, and scintillation-induced link fading.

To address building sway and therefore reduce pointing errors, accurate pointing and tracking mechanisms, multi-array transmitter and receiver, and/or wide beam profiles could be adopted.

In FSO links, phase and irradiance fluctuations experienced by the propagating optical beam make optical coherent detection less attractive, simply because it is sensitive to both signal amplitude and phase fluctuations thus the reasons for adopting the direct detection scheme in terrestrial FSO links.

The available options for mitigating the effect of channel fading in FSO links include but are not limited to increased transmit power, diversity (i.e., frequency, spatial, temporal, and polarisation) schemes, including the multiple-input-multiple-output (MIMO), hybrid RF-FSO links, aperture averaging, adaptive optics, and subcarrier time diversity, which are covered in Chapter 7.

The link performance using equal gain combining, optimal combining, or equivalently maximum ratio combining and selection combining diversity schemes for log-normal and gamma-gamma atmospheric channels employing a range of diverse techniques is also outlined in Chapter 7.

Chapter 8 is dedicated to VLC, a subject that in the last few years has witnessed an increased level of research activities. Put simply, VLC is the idea of using visible optical sources for illumination, wireless data communications, indoor localization, and sensing.

The main drivers for the VLC technology include the increasing popularity of solid-state and organic-based lights and the longer lifetime of high brightness LEDs compared to other existing light sources.

The multiple functionalities offered by LEDs has created a whole range of interesting applications, including home networking, car-to-car communication, high-speed communications in airplane cabins, in-train data communications, traffic light management, and medical and manufacturing communications, to name a few.

The levels of power efficiency and reliability offered by LEDs are superior compared to traditional incandescent light sources.

This chapter gives an overview of the VLC communication technology, highlighting the fundamental theoretical background, devices available, modulation and dimming techniques, and system performance analysis. Multiple-input, multiple-output, and cellular visible light communication systems are also covered in Chapter 8.

As outlined in Chapters 3, 6, and 7, FSO link performance is hampered by the atmospheric channel conditions, thus affecting the link range and availability.

However, in order to increase the link availability and the linkspan, the data can be transmitted via relays to end-users, which offers many unique advantages and also presents a number of fundamental challenges.

Chapter 9 presents an extensive review and discussion on the key aspects of FSO technology with relay focusing on optical networks and their topology, serial, and parallel relaying all-optical relay FSO links. The relay-based FSO link performance under turbulence is also investigated both theoretically and experimentally in Chapter 9.

The relevant and necessary Matlab codes are given in each chapter to enable the reader to carry out extensive simulations in order to better understand the topics.

Note that it is expected that the readers first study the theory and then use the Matlab codes for their needs.

Recent, relevant, and up-to-date references, which provide a guide for further reading, are also included at the end of each chapter. A complete list of common abbreviations used in the text is also provided.

Throughout the book, SI units are used. We would like to thank all the authors of all journals and conference papers, articles, and books we consulted in writing this second edition.

Special thanks to those authors, publishers, and companies who kindly granted permission for the reproduction of their figures. We would also like to extend our gratitude to all our past and current Ph.D. students for their immense contributions to the knowledge in OWC.

Their contributions have enriched the content of this book. Finally, we remain extremely grateful to our families and friends who have continued to be supportive and have provided needed encouragement.

In particular, our very special thanks go to Azar, Odunayo, and Kanchan for their continued patience and unconditional support, which has enabled us to finally complete this challenging task. Their support has been fantastic.

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