 | Ghassemlooy Z. Optical wireless communications: system and channel modelling with MATLAB / Z.Ghassemlooy, W.Popoola, S.Rajbhandari. - Boca Raton: CRC Press/Taylor & Francis, 2013. - lii, 517 p.: ill. - Incl. bibl. ref. - Ind.: p.497-517. - ISBN 978-1-4398-5188-3
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Preface ........................................................ xv
Authors ....................................................... xix
List of Figures ............................................. xxiii
List of Tables ............................................. xxxvii
Abbreviations ............................................... xxxix
Chapter 1 Introduction: Optical Wireless Communication
Systems ......................................................... 1
1.1 Wireless Access Schemes .................................... 1
1.2 A Brief History of OWC ..................................... 7
1.3 OWC/Radio Comparison ....................................... 8
1.4 Link Configuration ........................................ 11
1.5 OWC Application Areas ..................................... 19
1.6 Safety and Regulations .................................... 21
1.6.1 Maximum Permissible Exposures ...................... 25
1.7 OWC Challenges ............................................ 25
References ..................................................... 30
Chapter 2 Optical Sources and Detectors ....................... 35
2.1 Light Sources ............................................. 35
2.2 Light-Emitting Diode ...................................... 38
2.2.1 LED Structure ...................................... 41
2.2.2 Planar and Dome LED ................................ 42
2.2.3 Edge-Emitting LED .................................. 43
2.2.4 LED Efficiencies ................................... 44
2.2.4.1 Internal Quantum Efficiency ............... 44
2.2.4.2 External Quantum Efficiency ............... 45
2.2.4.3 Power Efficiency .......................... 45
2.2.4.4 Luminous Efficiency ....................... 46
2.2.4.5 LED Modulation Bandwidth .................. 47
2.3 The Laser ................................................. 48
2.3.1 Operating Principle of a Laser ..................... 48
2.3.2 Stimulated Emission ................................ 49
2.3.2.1 Population Inversion ...................... 50
2.3.3 Optical Feedback and Laser Oscillation ............. 50
2.3.4 Basic Semiconductor Laser Structure ................ 51
2.3.5 The Structure of Common Laser Types ................ 53
2.3.5.1 Fabry-Perot Laser ......................... 53
2.3.5.2 Distributed Feedback Laser ................ 54
2.3.5.3 Vertical-Cavity Surface-Emitting Laser .... 55
2.3.5.4 Superluminescent Diodes ................... 56
2.3.6 Comparison of LED and Laser Diodes ................. 57
2.4 Photodetectors ............................................ 57
2.4.1 PIN Photodetector .................................. 59
2.4.2 APD Photodetector .................................. 61
2.5 Photodetection Techniques ................................. 62
2.5.1 Direct Detection ................................... 63
2.5.2 Coherent Detection ................................. 63
2.5.2.1 Heterodyne Detection ...................... 64
2.5.2.2 Homodyne Detection ........................ 66
2.6 Photodetection Noise ...................................... 66
2.6.1 Photon Fluctuation Noise ........................... 67
2.6.2 Dark Current and Excess Noise ...................... 68
2.6.3 Background Radiation ............................... 70
2.6.4 Thermal Noise ...................................... 70
2.6.5 Intensity Noise .................................... 71
2.6.6 Signal-to-Noise Ratio .............................. 72
2.7 Optical Detection Statistics .............................. 72
References ..................................................... 74
Chapter 3 Channel Modelling ................................... 77
3.1 Indoor Optical Wireless Communication Channel ............. 77
3.1.1 LOS Propagation Model .............................. 81
3.1.2 Non-LOS Propagation Model .......................... 84
3.1.3 Ceiling Bounce Model ............................... 95
3.1.4 Hayasaka-Ito Model ................................. 96
3.1.5 Spherical Model .................................... 97
3.2 Artificial Light Interference ............................. 99
3.2.1 Incandescent Lamp ................................. 100
3.2.2 Fluorescent Lamp Driven by Conventional Ballast ... 101
3.2.3 Fluorescent Lamp Model ............................ 102
3.3 Outdoor Channel .......................................... 107
3.3.1 Atmospheric Channel Loss .......................... 107
3.3.2 Fog and Visibility ................................ 111
3.3.3 Beam Divergence ................................... 120
3.3.4 Optical and Window Loss ........................... 125
3.3.5 Pointing Loss ..................................... 125
3.3.6 The Atmospheric Turbulence Models ................. 126
3.3.6.1 Log-Normal Turbulence Model .............. 131
3.3.6.2 Spatial Coherence in Weak Turbulence ..... 135
3.3.6.3 Limit of Log-Normal Turbulence Model ..... 137
3.3.6.4 The Gamma-Gamma Turbulence Model ......... 138
3.3.6.5 The Negative Exponential Turbulence
Model .................................... 142
3.3.7 Atmospheric Effects on OWC Test Bed ................ 143
3.3.7.1 Demonstration of Scintillation Effect
on Data Carrying Optical Radiation ....... 146
References ....................................................
Chapter 4 Modulation Techniques .............................. 161
4.1 Introduction ............................................. 161
4.2 Analogue Intensity Modulation ............................ 164
4.3 Digital Baseband Modulation Techniques ................... 167
4.3.1 Baseband Modulations .............................. 167
4.3.2 On-Off Keying ..................................... 168
4.3.3 Error Performance on Gaussian Channels ............ 172
4.4 Pulse Position Modulation ................................ 178
4.4.1 Error Performance on Gaussian Channels ............ 182
4.4.2 PPM Variants ...................................... I86
4.4.2.1 Multilevel PPM ........................... 187
4.4.2.2 Differential PPM ......................... 188
4.4.2.3 Differential Amplitude Pulse Position
Modulation ............................... 189
4.5 Pulse Interval Modulation ................................ 189
4.5.1 Error Performance on Gaussian Channels ............ 195
4.5.1.1 DPIM with No Guard Band .................. 199
4.5.1.2 DPIM with One Guard Slot ................. 200
4.5.2 Optimum Threshold Level ........................... 202
4.6 Dual-Header PIM (DH-PIM) ................................. 206
4.6.1 Spectral Characteristics .......................... 209
4.6.2 Error Performance on Gaussian Channels ............ 211
4.7 Multilevel DPIM .......................................... 215
4.8 Comparisons of Baseband Modulation Schemes ............... 217
4.8.1 Power Efficiency .................................. 217
4.8.2 Transmission Bandwidth Requirements ............... 219
4.8.3 Transmission Capacity ............................. 222
4.8.4 Transmission Rate ................................. 223
4.8.5 Peak-to-Average Power Ratio ....................... 224
4.9 Subcarrier Intensity Modulation .......................... 225
4.10 Orthogonal Frequency Division Multiplexing ............... 229
4.11 Optical Polarization Shift Keying ........................ 233
4.11.1 Binary PolSK ...................................... 234
4.11.2 Bit Error Rate Analysis ........................... 239
4.11.3 MPolSK ............................................ 241
4.11.4 Differential Circle Polarization Shift Keying ..... 245
4.11.5 Error Probability Analysis ........................ 247
Appendix 4.A .................................................. 248
4.A.1 Derivation of Slot Autocorrelation Function of
DPIM(IGS) ......................................... 248
Appendix 4.B .................................................. 252
4.B.1 PSDofDH-PIM ....................................... 252
4.B.1.1 Fourier Transform of DH-PIM .............. 252
4.B.1.2 Power Spectral Density of DH-PIM ......... 252
4.B.1.3 Further Discussion on the PSD
Expression ............................... 260
References .................................................... 261
Chapter 5 System Performance Analysis: Indoor ................ 267
5.1 Effect of Ambient Light Sources on Indoor OWC Link
Performance .............................................. 267
5.2 Effect of FLI without Electrical High-Pass Filtering ..... 268
5.2.1 Matched Filter Receiver ........................... 269
5.3 Effect of Baseline Wander without FLI .................... 277
5.4 Effect of FLI with Electrical High-Pass Filtering ........ 286
5.5 Wavelet Analysis ......................................... 293
5.5.1 The Continuous Wavelet Transform .................. 294
5.5.2 The Discrete Wavelet Transform .................... 297
5.5.3 DWT-Based Denoising ............................... 298
5.5.4 Comparative Study of DWT and HPF .................. 303
5.5.5 Experimental Investigations ....................... 305
5.6 Link Performance for Multipath Propagation ............... 310
5.6.1 OOK ............................................... 310
5.6.2 PPM ............................................... 317
5.6.3 DPIM .............................................. 319
5.7 Mitigation Techniques .................................... 320
5.7.1 Filtering ......................................... 321
5.7.2 Equalization ...................................... 323
5.7.2.1 The Zero Forcing Equalizer ............... 323
5.7.2.2 Minimum Mean Square Error Equalizer ...... 325
5.7.2.3 Decision Feedback Equalizer .............. 326
5.8 Equalization as a Classification Problem ................. 327
5.9 Introduction to Artificial Neural Network ................ 327
5.9.1 Neuron ............................................ 328
5.9.2 ANN Architectures ................................. 329
5.10 Training Network ......................................... 330
5.10.1 Backpropagation Learning .......................... 331
5.11 The ANN-Based Adaptive Equalizer ......................... 332
5.11.1 Comparative Study of the ANN- and FIR-Based
Equalizers ........................................ 340
5.11.2 Diversity Techniques .............................. 341
References .................................................... 342
Chapter 6 FSO Link Performance under the Effect of
Atmospheric Turbulence ........................................ 347
6.1 On-Off Keying ............................................ 348
6.1.1 OOK in a Poisson Atmospheric Optical Channel ...... 348
6.1.2 OOK in a Gaussian Atmospheric Optical Channel ..... 350
6.2 Pulse Position Modulation ................................ 354
6.3 Subcarrier Intensity Modulation .......................... 358
6.3.1 SIM Generation and Detection ...................... 359
6.3.2 SIM-FSO Performance in Log-Normal Atmospheric
Channel ........................................... 362
6.3.3 Bit Error Probability Analysis of SIM-FSO ......... 366
6.3.3.1 BPSK-Modulated Subcarrier ................ 367
6.3.3.2 M-Ary PSK-Modulated Subcarrier ........... 373
6.3.3.3 DPSK-Modulated Subcarrier ................ 374
6.3.3.4 Multiple SIM Performance Analysis ........ 376
6.3.3.5 Outage Probability in Log-Normal
Atmospheric Channels ..................... 377
6.3.4 SIM-FSO Performance in Gamma-Gamma and Negative
Exponential Atmospheric Channels .................. 380
6.3.5 Outage Probability in Negative Exponential Model
Atmospheric Channels .............................. 383
6.4 Atmospheric Turbulence-Induced Penalty ................... 384
Appendix 6.A .................................................. 388
Appendix 6.B .................................................. 388
6.B.1 MATLAB Scripts for Sections 6.3.2, 6.3.3.2 and
6.3.3.3 ........................................... 388
6.B.1.1 Section 6.3.2 ............................ 388
6.B.1.2 Sections 6.3.3.2 and 6.3.3.3 ............. 389
References .................................................... 394
Chapter 7 Outdoor OWC Links with Diversity Techniques ........ 397
7.1 Atmospheric Turbulence Mitigation Techniques ............. 397
7.2 Receiver Diversity in Log-Normal Atmospheric Channels .... 400
7.2.1 Maximum Ratio Combining ........................... 402
7.2.2 Equal Gain Combining .............................. 404
7.2.3 Selection Combining ............................... 406
7.2.4 Effect of Received Signal Correlation on Error
Performance ....................................... 407
7.2.5 Outage Probability with Receiver Diversity in a
Log-Normal Atmospheric Channel .................... 408
7.3 Transmitter Diversity in a Log-Normal Atmospheric
Channel .................................................. 409
7.4 Transmitter-Receiver Diversity in a Log-Normal
Atmospheric Channel ...................................... 410
7.5 Results and Discussions of SIM-FSO with Spatial
Diversity in a Log-Normal Atmospheric Channel ............ 411
7.6 SIM-FSO with Receiver Diversity in Gamma-Gamma and
Negative Exponential Atmospheric Channels ................ 416
7.6.1 BER and Outage Probability of BPSK-SIM with
Spatial Diversity ................................. 416
7.6.2 BER and Outage Probability of DPSK-SIM in
Negative Exponential Channels ..................... 419
7.7 Terrestrial Free Space Optical Links with Subcarrier
Time Diversity ........................................... 425
7.7.1 Error Performance with STDD ....................... 425
7.7.1.1 Error Performance of Short-Range Links ... 427
7.7.1.2 Error Performance of Long-Range Links .... 428
7.7.1.3 Results and Discussion for Short-Range
Links .................................... 429
7.7.1.4 Results and Discussion for Long-Range
Links .................................... 430
7.8 Aperture Averaging ....................................... 432
7.8.1 Plane Wave ........................................ 432
7.8.2 Spherical Wave .................................... 433
7.8.3 Gaussian Beam Wave ................................ 434
Appendix 7.A .................................................. 435
7.A.1 Sum of Log-Normal Distribution Mean and Variance
Calculation ....................................... 435
Appendix 7.B .................................................. 437
7.B.1 PDF of Imax = max {Ii}i=1N, for Log-Normal-
Distributed Variables ............................. 437
Appendix 7.C .................................................. 438
7.C.1 PDF of Imax = max {Ii}i=1N for Negative
Exponential Distributed Variables ................. 438
References .................................................... 438
Chapter 8 Visible Light Communications ....................... 443
8.1 Introduction ............................................. 443
8.2 System Description ....................................... 448
8.2.1 VLC System Model .................................. 452
8.2.2 SNR Analysis ...................................... 463
8.2.3 Channel Delay Spread .............................. 464
8.3 System Implementations
8.3.1 Bit Angle Modulation .............................. 469
8.3.2 Pulse Modulation Schemes .......................... 470
8.3.3 PWM with Discrete Multitone Modulation ............ 472
8.3.4 Multilevel PWM-PPM ................................ 474
8.3.5 PWM with NRZ-OOK .................................. 476
8.4 Multiple-Input-Multiple-Output VLC ....................... 477
8.5 Home Access Network ...................................... 486
References
Index ......................................................... 497
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