Fundamentals of DSL Technology

au1913_fm.pdf......Page 1
Fundamentals of DSL Technology......Page 3
Dedications......Page 5
Acknowledgments......Page 6
Foreword......Page 7
References......Page 8
Contents......Page 9
CONTENTS......Page 10
Contents......Page 0
1.1 How the Telephony System Is Typically Constructed......Page 11
1.1.1 Network Structure......Page 12
1.1.2.1 Line Interface Circuits......Page 13
1.1.3 Cables......Page 14
1.1.4 Network Demarcation Points......Page 16
1.1.5.1 Bus Topology......Page 18
1.1.5.4 Terminal Equipment Impedance......Page 19
1.1.5.7 “Off-Hook” State......Page 20
1.2 Speech Signals......Page 22
1.3.1 Two-Wire Transmission......Page 23
1.3.3 Conceptual Hybrid Circuit......Page 24
1.3.5 Choice of Balance Impedance......Page 25
1.3.7 Gains in the Hybrids......Page 26
1.4.2 Resistive Feeding from the Local Exchange......Page 27
1.4.5 Resistance of the Terminal Equipment......Page 28
1.5.1 Corrosion of Cable Joints......Page 29
1.6 Ringing......Page 30
1.7 Ring Trip......Page 31
1.9.1 Pulse (Loop Disconnect) Dialing......Page 32
1.9.1.1 High Voltage Transients Due to Pulse Dialing......Page 33
1.9.2 Tone Dialing......Page 34
1.11 Telephony Speech Coding......Page 35
1.13 Testing......Page 36
1.14 Overload......Page 37
1.16 CLASS Signalling......Page 38
References......Page 39
CONTENTS......Page 41
2.1 Historical Use of the Copper Network Û Digital vs. Analog......Page 42
2.2.1 Differential Mode Signalling......Page 43
2.2.2 Insulation, Core Assembly, and Shielding of Twisted Pairs......Page 45
2.2.4 Wire Diameter and Gauge......Page 46
2.2.6 Load Coils......Page 47
2.2.8 Shared Line Multiplexers......Page 48
2.3.1 Primary Parameters of Lines......Page 49
2.3.2 Line Terminated by Its Characteristic Impedance......Page 50
2.3.3 Characteristic Impedance in POTS Band......Page 51
2.3.5 Transmission of Signals Across the Line......Page 52
2.3.6 Power Transmission Across Lines......Page 54
2.3.7 ABCD Line Modelling......Page 56
2.3.8 Transfer Function and Insertion Loss Associated with DSL Lines......Page 58
2.3.9 Scattering Parameters......Page 59
2.3.10 Impedance and Admittance Modelling Parameters......Page 63
2.4.1.1 Empirical Model for Resistance......Page 64
2.4.3 The British Telecom Model #1 Parameters......Page 65
2.4.4 Examples of Cable Modelling Using the BT #0 Model......Page 66
2.4.6 The KPN Model #0......Page 67
2.4.8 Examples of Cable Modelling Using the KPN #1 Model......Page 68
2.5.1 Examples of Loop Configurations......Page 71
2.5.3 Insertion Loss of Some European Reference Loops......Page 74
References......Page 78
CONTENTS......Page 79
3.1 Crosstalk......Page 80
3.1.1 Empirical Models......Page 82
3.1.1.2 Cable Filling and the Meaning of N......Page 86
3.1.1.4 Verification......Page 87
3.1.2 Summary of Crosstalk PSD Formulae......Page 88
3.2 Impulsive Noise......Page 89
3.4.1 Screening (Does Not Work)......Page 90
3.4.4 Band Duplexing......Page 91
3.5.1 Use of Noise Models......Page 92
3.5.2.3 Standards......Page 93
3.5.3 Impulsive Noise......Page 94
3.6.1 Worst-Case Length for FEXT Coupling......Page 95
3.6.2 Length Dependence of NEXT......Page 96
3.6.3 NEXT and FEXT as Scattering......Page 97
3.6.3.1 NEXT......Page 101
3.6.3.2 FEXT......Page 102
References......Page 103
4.1 Introduction......Page 105
4.2 Information in Digital Communication Systems......Page 106
4.3 Entropy and Information......Page 107
4.4 Transmission Rate and Channel Capacity......Page 109
4.5 Channel Capacity in Presence of Additive Gaussian Noise......Page 110
4.6.1 PAM Error Probability......Page 113
4.6.2 QAM/CAP Error Probability......Page 116
4.6.3 Ideal DFE Data Rate Calculations......Page 119
4.6.4 Ideal DMT Data Rate Calculations......Page 122
4.7 Examples of Data Rate Calculations......Page 123
References......Page 125
CONTENTS......Page 126
5.2 History......Page 127
5.3.1 Fiber......Page 129
5.3.3 Cable Modem......Page 130
5.4.1 Introduction......Page 132
5.4.3 Basic Rate ISDN (BRI)......Page 134
5.4.4 HDSL......Page 135
5.4.5 HDSL2 and HDSL4......Page 136
5.4.7 G.shdsl......Page 137
5.4.8 ADSL......Page 138
5.4.10 ADSL2, ADSL2plus......Page 140
5.4.12.1 Spectrum Management......Page 141
5.4.12.4 Ethernet in the First Mile (EFM)......Page 142
5.5.1.2 Trellis-Coded Modulation (Encoder and Decoder)......Page 143
5.5.1.5 Transmit Analog Front End (AFE)......Page 144
5.5.2 Passband Single-Carrier Systems......Page 145
5.5.2.3 Carrier Recovery......Page 146
5.5.4 Closing Remarks......Page 147
References......Page 148
CONTENTS......Page 150
6.2.1 QAM......Page 151
6.2.1.1 Transmitter......Page 153
6.2.1.2 Constellation Encoder (Mapper)......Page 155
6.2.1.3 Spectrum Shaping Filters......Page 157
6.2.1.4 Receiver......Page 159
6.2.1.5 Demodulator......Page 160
6.2.1.6 Equalizer......Page 161
6.2.1.7 Decision Circuits (Slicers) and Constellation Decoder......Page 162
6.2.2 PAM......Page 164
6.2.3 CAP......Page 166
6.3 Main Parameters of SCM Signals......Page 168
6.4.1 Error Performance......Page 171
6.4.2 Transport Capability (Bit Rate)......Page 173
6.5.1 Blind Equalization......Page 174
6.5.2 Multi-Symbol Constellation Encoding......Page 175
6.5.3 Spectrum Allocation and PSD Shaping......Page 176
6.5.5 Initialization......Page 177
6.5.6 Burst Mode SCM Transceivers......Page 178
6.5.7.1 Operation of the Transceiver......Page 179
6.5.7.2 Frame Splitting and Recovering......Page 180
6.5.7.3 Transport Capability......Page 181
6.6 Annex I: Constellation Diagrams......Page 182
References......Page 185
CONTENTS......Page 187
7.2 Basics of Multi-Carrier Modulation......Page 188
7.3 Discrete Multi-Tone (DMT)......Page 192
7.3.1 Digital Duplexing......Page 199
7.3.1.1 Cyclic Suffix......Page 200
7.3.1.3 Cyclic Extension......Page 202
7.3.2 Peak-to-Average Ratio......Page 203
7.3.2.1 PAR Reduction Techniques......Page 204
7.4 Initialization......Page 206
7.4.3 Transceiver Training......Page 207
7.4.4.1 Channel Identification......Page 208
7.4.4.2 Noise Identification......Page 209
7.4.4.4 Bit Allocation to Maximize the Bit Rate at a Target Noise Margin......Page 210
7.5 Steady-State Adaptation......Page 212
7.5.1 Bit Swapping......Page 213
7.6 Summary......Page 214
References......Page 215
8.1 Introduction......Page 217
8.2.1 Uncoded Modulation and Coded Modulation......Page 218
Example 8.1: Four-State Coded 8-PSK......Page 219
8.2.3 Set Partitioning......Page 220
8.2.4 General Structure of TCM Encoders......Page 223
8.2.5 Free Euclidean Distance......Page 224
8.2.6 Code Search and Optimum Codes......Page 226
8.2.7 Performance of TCM Schemes with Different Symbol Dimensions......Page 228
8.3.1 TCM Encoder......Page 229
8.3.3 Convolutional Encoder......Page 230
8.4.1 Bit Allocations and Tone Ordering......Page 231
8.4.3.1 Even Values of b......Page 232
8.4.4 Discussion......Page 233
8.5 Conclusions......Page 236
References......Page 237
CONTENTS......Page 239
9.1 Introduction......Page 240
9.2.1 Galois Fields......Page 241
Example 9.1......Page 242
9.2.2 Cyclic Redundancy Check (CRC)......Page 244
9.2.3 An Upper Bound on the Probability of an Undetected Error......Page 247
Example 9.2......Page 248
9.2.4 Exact Calculation of the Probability of Undetected Error......Page 250
Example 9.3......Page 251
9.2.5 Reed–Solomon Codes......Page 252
9.2.6 Decoding ReedÒSolomon Codes......Page 254
9.3 Forward Error Correction Coding Gain......Page 259
9.2.7 Consequences of Uncorrectable Errors......Page 255
9.4 Interleaving......Page 264
9.4.1 Optimum Memory Implementation Using TongÌs Method......Page 267
9.4.2 Forney's Triangular Interleaver......Page 268
9.4.4 Erasures......Page 271
9.5 Concatenated Coding......Page 272
References......Page 275
CONTENTS......Page 277
10.1 Introduction......Page 278
10.2.1 LDPC Codes and Belief-Propagation (BP) Decoding......Page 279
10.2.2 The BP Decoding Algorithm in the Log Domain......Page 281
10.2.2.1 LLR-BP Decoding Based on the tanh Rule......Page 282
10.2.2.3 LLR-BP Decoding Based on the Jacobian Approach......Page 283
10.2.3 Turbo Codes and Iterative BCJR Decoding......Page 284
10.2.4.1 The Log-MAP Decoding Algorithm......Page 287
10.2.4.2 The Max-Log-MAP Decoding Algorithm......Page 289
10.3 Error-Correction Coding for Digital Subscriber Lines......Page 290
10.4 Transmitter and Receiver Functions......Page 292
10.5 Performance......Page 297
10.5.3 Latency......Page 298
10.6 Complexity......Page 301
References......Page 302
CONTENTS......Page 304
11.2.1 Signal Representation......Page 305
11.2.2 Channel Model......Page 306
11.2.4 Causality and Signal Delay......Page 308
11.3.1 Matched Filters......Page 309
11.3.2 Zero-Forcing Equalization (ZFE)......Page 311
11.3.3 MMSE Equalization......Page 313
11.3.4 MAP and ML Detection......Page 315
11.4 Equalizer Structures......Page 316
11.4.2 Decision Feedback Equalization......Page 317
11.4.3 Noise Prediction Filters......Page 321
11.4.4 Tomlinson-Harashima Precoding......Page 323
11.4.5 Maximum Likelihood Detection......Page 324
11.4.6 Frequency Domain Equalization......Page 326
11.4.7 Impulse Shortening Equalization......Page 327
11.5.1 MMSE Equalizer Design Algorithms......Page 332
11.5.2 Channel Probing......Page 334
11.6.1 The LMS Algorithm......Page 336
11.6.2 Equalizer Training......Page 340
11.6.3 Blind Equalizer Training......Page 341
11.7.1 Linear Versus Decision Feedback Equalizers......Page 343
11.7.2 Zero-Forcing Versus MMSE Equalization......Page 344
11.7.3 Fractionally Spaced Versus T-Spaced Equalizers......Page 347
11.7.4 Impulse Shortening Equalization......Page 350
11.7.5 Summary......Page 353
References......Page 354
CONTENTS......Page 356
12.1 Overview......Page 357
12.1.1 Quality of Timing Error Signal Generation......Page 358
12.1.2 Examples......Page 359
12.2.1 Maximum-Likelihood Timing Recovery......Page 360
12.2.2 Band-Edge Energy Maximization......Page 364
12.2.2.1 The Band-Edge Energy......Page 365
12.2.2.2 BETR Timing Function for QAM......Page 367
12.2.3 Timing Signals Based on Nonlinearity-Induced Spectral Line......Page 370
12.2.3.1 Analysis of Squarer-Induced Spectral Line — Without Noise......Page 371
12.2.4 Timing Recovery Based on Equalizer Taps......Page 376
12.2.5 The Gardner Timing Function......Page 380
12.2.6 Mueller –Muller-Based Methods......Page 381
12.2.7 Gradient-Descent Timing Recovery......Page 386
12.3 DMT Synchronization......Page 391
12.3.1 Synchronization to the DMT Symbol......Page 393
12.3.2 Effect of Timing Phase on a Demodulated DMT Symbol......Page 394
12.3.3 Pilot-Based Timing Acquisition and Tracking......Page 396
12.3.4 Nonpilot-Based Timing Acquisition and Tracking......Page 397
12.3.4.1 Effect of Timing Jitter on DMT Performance......Page 398
References on BETR Methods......Page 399
References on Gardner Methods......Page 400
References on DMT......Page 401
References on NISL......Page 402
CONTENTS......Page 403
13.1 Introduction......Page 404
13.1.1 Short RFI Ingress Analysis......Page 405
13.1.2.1 AM Radio......Page 406
13.1.2.2 Amateur (“HAM”) Radio......Page 408
13.2 Suppression Strategies Û An Overview......Page 410
13.3.1 Common-Mode Choke......Page 411
13.3.3 Active Analog Reference-Based Cancellation......Page 412
13.3.3.1 Coupling Mechanism and Model......Page 413
13.3.3.2 An Example: Mixed-Signal RFI Canceller......Page 415
13.4 Digital Suppression Techniques......Page 419
13.5.1 Digital Receiver Filtering......Page 420
13.5.3 Receiver Windowing......Page 421
13.6 Active Digital RFI Cancellation......Page 424
13.6.2 Deterministic RF Signal Model......Page 425
13.6.2.1 Appendix: Taylor Parameterization......Page 427
13.6.3 Stochastic RF Signal Model......Page 429
13.6.3.2 DFT Processing......Page 430
13.6.3.3 LMMSE Estimator......Page 431
13.6.3.4 Optimal Low-Rank Approximation......Page 433
13.6.3.5 Rank of the RFI......Page 435
13.6.3.6 Partial RFI Cancellation......Page 436
13.6.4 Nonmodel-Based RFI Cancellation......Page 437
13.6.4.1 Convergence Speed......Page 438
13.6.4.2 Canceller Performance......Page 440
13.6.5 Frequency Invariance......Page 441
13.7 Alternative Methods to Suppress RFI......Page 442
13.8.1.1 Passive RFI Suppression......Page 443
13.8.1.2 Active RFI Cancellation Methods for DMT......Page 446
13.8.2 Complexity......Page 449
13.8.2.2 Active Methods for DMT......Page 450
References......Page 452