Wireless Optical Communication Systems

wireless Optical Communication Systems Addresses The Problem Of Designing Efficient Signaling And Provides A Link Between The Areas Of Communication Theory And Modem Design For Amplitude Constrained Linear Optical Intensity Channel. Topics Include Historical Perspective, Channel Impairments, Amplitude Constraints And The Characteristics Of Popular Optoelectronic Components. A Variety Of Wireless Optical Channel Topologies Are Presented Along With A Survey And Analysis Of Present Day Signalling Techniques Employed For These Channels. The Author Provides A Unifying Framework For Signalling Design Which Allows The Channel Constraints To Be Represented Geometrically And Permits The Use Of Modem Design Principles From Electrical Channels. Modulation Schemes Are Designed Using The Formalism Of Lattice Codes And A Design Process For Signalling Sets Is Specified. the Use Of Multiple-input/multiple-output (mimo) Wireless Optical Channels To Improve The Spectral Efficiency Of Links Is Explored. The Basic Spatio-temporal Modem Design Problem Is Specified And A Spatial Multiplexing Gain Is Quantified. New Spatial Discrete Multitone Modulation Is Proposed And The Unique Features Are Discussed. Based On Measurements On An Experimental Prototype, A Channel Model Is Formulated And A Realizable Spatio-temporal Coding Scheme Is Simulated To Quantify Performance Gains. this Volume Is Organized For Professional And Academic Readers Engaged In Modem Design For Wireless Optical Intensity Channels. Significant Background Material Is Presented On Both The Properties As Well As On Fundamental Communications Principles. Wireless Optical Communication Systems Can Be Used By Physicists And Experimentalists As An Introduction To Signalling Design As Well As Communication Systems Designers. Team DDU......Page 1 Dedication......Page 6 Table Of Contents......Page 8 Preface......Page 12 Part I Introduction......Page 14 1. INTRODUCTION......Page 16 1.1 A Brief History of Wireless Optical Communications......Page 18 1.2 Overview......Page 20 2. WIRELESS OPTICAL INTENSITY CHANNELS......Page 22 2.1 Wireless Optical Intensity Channels......Page 23 2.2 Optoelectronic Components......Page 29 2.3 Noise......Page 40 2.4 Channel Topologies......Page 44 2.5 Summary......Page 48 3.1 Communication System Model......Page 52 3.2 Bandwidth......Page 60 3.3 Example Modulation......Page 64 3.4 The Communication System Design Problem......Page 77 Part II Signalling Design......Page 80 4.1 Signal Space of Optical Intensity Signals......Page 82 4.2 Examples......Page 90 4.3 Conclusions......Page 94 5. LATTICE CODES......Page 96 5.1 Definition of Lattice Codes......Page 97 5.2 Constellation Figure of Merit? Gain......Page 99 5.4 Spectral Considerations......Page 101 5.6 Continuous Approximation to Optical Power Gain......Page 103 5.7 Coding Gain......Page 104 5.8 Shaping Gain......Page 105 5.9 Shaping Gain: Expression......Page 106 5.10 Shaping Gain: Peak-Symmetric Schemes......Page 107 5.12 Example Lattice Codes......Page 108 5.13 Conclusions......Page 115 5.A Continuous Approximation of the Power Spectral Density......Page 117 6.1 Background......Page 120 6.2 Problem Definition......Page 122 6.3 BandwidthConstraint......Page 123 6.4 Upper bound on Channel Capacity......Page 124 6.5 Lower bound on Channel Capacity......Page 128 6.6 Examples and Discussion......Page 130 6.7 Conclusions......Page 137 Part III Multi-Element Techniques......Page 138 7. THE MULTIPLE-INPUT / MULTIPLE-OUTPUT WIRELESS OPTICAL CHANNEL......Page 140 7.1 Previous Work......Page 141 7.2 The MIMO Wireless Optical Channel......Page 143 7.3 Design Challenges......Page 149 7.4 Pixel-Matched System......Page 151 7.5 The Pixelated Wireless Optical Channel......Page 153 7.6 Conclusions......Page 159 8.1 Experimental Prototype......Page 162 8.2 Channel Model......Page 166 8.3 Pixel-Matched Systems......Page 177 8.4 Pixelated Wireless Optical Channel......Page 178 8.5 Conclusions......Page 187 9.1 Conclusions......Page 190 9.2 Future Work......Page 191 References......Page 194 Index......Page 208 About the Author......Page 210 Team DDU Wireless Optical Communication Systems 1 Cover 1 Dedication 6 Table Of Contents 8 Preface 12 Part I Introduction 14 1. INTRODUCTION 16 1.1 A Brief History of Wireless Optical Communications 18 1.2 Overview 20 2. WIRELESS OPTICAL INTENSITY CHANNELS 22 2.1 Wireless Optical Intensity Channels 23 2.2 Optoelectronic Components 29 2.3 Noise 40 2.4 Channel Topologies 44 2.5 Summary 48 3. AN INTRODUCTION TO OPTICAL INTENSITY SIGNALLING 52 3.1 Communication System Model 52 3.2 Bandwidth 60 3.3 Example Modulation 64 3.4 The Communication System Design Problem 77 Part II Signalling Design 80 4. OPTICAL INTENSITY SIGNAL SPACE MODEL 82 4.1 Signal Space of Optical Intensity Signals 82 4.2 Examples 90 4.3 Conclusions 94 5. LATTICE CODES 96 5.1 Definition of Lattice Codes 97 5.2 Constellation Figure of Merit? Gain 99 5.3 Baseline Constellation 101 5.4 Spectral Considerations 101 5.5 Gain versus a Baseline Constellation 103 5.6 Continuous Approximation to Optical Power Gain 103 5.7 Coding Gain 104 5.8 Shaping Gain 105 5.9 Shaping Gain: Expression 106 5.10 Shaping Gain: Peak-Symmetric Schemes 107 5.11 Opportunistic Secondary Channels 108 5.12 Example Lattice Codes 108 5.13 Conclusions 115 5.A Continuous Approximation of the Power Spectral Density 117 6. CHANNEL CAPACITY 120 6.1 Background 120 6.2 Problem Definition 122 6.3 BandwidthConstraint 123 6.4 Upper bound on Channel Capacity 124 6.5 Lower bound on Channel Capacity 128 6.6 Examples and Discussion 130 6.7 Conclusions 137 Part III Multi-Element Techniques 138 7. THE MULTIPLE-INPUT / MULTIPLE-OUTPUT WIRELESS OPTICAL CHANNEL 140 7.1 Previous Work 141 7.2 The MIMO Wireless Optical Channel 143 7.3 Design Challenges 149 7.4 Pixel-Matched System 151 7.5 The Pixelated Wireless Optical Channel 153 7.6 Conclusions 159 8. PROTOTYPE MIMO OPTICAL CHANNEL: MODELLING & SPATIO-TEMPORAL CODING 162 8.1 Experimental Prototype 162 8.2 Channel Model 166 8.3 Pixel-Matched Systems 177 8.4 Pixelated Wireless Optical Channel 178 8.5 Conclusions 187 9. CONCLUSIONS AND FUTURE DIRECTIONS 190 9.1 Conclusions 190 9.2 Future Work 191 References 194 Index 208 About the Author 210 Team DDU 1 The use of optical free-space emissions to provide indoor wireless com- nications has been studied extensively since the pioneering work of Gfeller and Bapst in 1979 [1]. These studies have been invariably interdisciplinary - volving such far flung areas such as optics design‚ indoor propagation studies‚ electronics design‚ communications systems design amongothers. The focus of this text is on the design of communications systems for indoor wireless optical channels. Signalling techniques developed for wired fibre optic n- works are seldom efficient since they do not consider the bandwidth restricted nature of the wireless optical channel. Additionally‚ the elegant design meth- ologies developed for electrical channels are not directly applicable due to the amplitude constraints of the optical intensity channel. This text is devoted to presenting optical intensity signalling techniques which are spectrally efficient‚ i. e. ‚ techniques which exploit careful pulse design or spatial degrees of freedom to improve data rates on wireless optical channels. The material presented here is complementary to both the comprehensive work of Barry [2] and to the later book by Otte et al. [3] which focused prim- ily on the design of the optical and electronic sub-systems for indoor wireless optical links. The signalling studies performed in these works focused p- marily on the analysis of popular signalling techniques for optical intensity channels and on the use of conventional electrical modulation techniques with some minor modifications (e. g. ‚ the addition of a bias). This volume addresses the problem of designing efficient signalling and provides a link between the areas of communication theory and modem design for amplitude constrained linear optical intensity channel. It provides practical guidelines for the design of signalling sets for wireless optical intensity channels. "Wireless Optical Communication Systems addresses the problem of designing efficient signaling and provides a link between the areas of communication theory and modern design for amplitude constrained linear optical intensity channels."--Résumé de l'éditeur "Wireless Optical Communication Systems addresses the problem of designing efficient signaling and provides a link between the areas of communication theory and modern design for amplitude constrained linear optical intensity channels."--Jacket In recent years, there has been a migration of computing power from the desktop to portable, mobile formats.