This exciting and comprehensive overview describes the underlying principles, implementation details, and key enhancing features of the new IEEE 802.11n standard, which has been created to significantly improve network throughput. A detailed discussion of important strength and reliability enhancing features is given in addition to a clear summary of any issues. Advanced topics are also covered. With numerous examples and simulation results included to highlight the benefits of the new features, this is an ideal reference for designers of Wireless Local Area Network (LAN) equipment, and network managers whose systems adopt the new standard. It is also a useful distillation of 802.11n technology for graduate students and researchers in the field of wireless communication.
Author(s): Eldad Perahia, Robert Stacey
Edition: 1
Year: 2008
Language: English
Pages: 416
Cover......Page 1
Half-title......Page 3
Title......Page 5
Copyright......Page 6
Brief contents......Page 9
Contents......Page 11
Foreword......Page 21
Preface......Page 25
Abbreviations......Page 27
1 Introduction......Page 33
1.1 History of IEEE 802.11......Page 35
1.2.1 The High Throughput Study Group......Page 37
1.2.2 Formation of the High Throughput Task Group (TGn)......Page 38
1.2.3 Call for proposals......Page 40
1.2.4 Handheld devices......Page 41
1.2.6 802.11n amendment drafts......Page 42
1.3 Environments and applications for 802.11n......Page 43
1.4 Major features of 802.11n......Page 47
1.5 Outline of chapters......Page 49
References......Page 51
Part I Physical layer......Page 53
2.1 Background......Page 55
2.2 Comparison to single carrier modulation......Page 57
References......Page 59
3.2 MIMO basics......Page 61
3.3 SDM basics......Page 63
3.4 MIMO environment......Page 65
3.5 802.11n propagation model......Page 67
3.5.1 Impulse response......Page 68
3.5.2 Antenna correlation......Page 70
3.5.2.1 Correlation coefficient......Page 71
3.5.3.1 Modified Doppler model for channel model F......Page 73
3.5.4.1 Phase noise......Page 75
3.5.4.2 Power amplifier non-linearity......Page 76
3.5.5 Path loss......Page 78
3.6 Linear receiver design......Page 79
3.7 Maximum likelihood estimation......Page 81
References......Page 83
Appendix 3.1: 802.11n channel models......Page 84
4.1.1 Short Training field......Page 90
4.1.2 Long Training field......Page 93
4.1.3 Signal field......Page 96
4.1.4 Data field......Page 97
4.1.5 Packet encoding process......Page 98
4.1.6 Receive procedure......Page 100
4.2.1 Non-HT portion of the MF preamble......Page 102
4.2.1.1 Cyclic shifts......Page 104
4.2.1.2 Legacy compatibility......Page 105
4.2.1.3 Non-HT Short Training field......Page 107
4.2.1.5 Non-HT Signal field......Page 108
4.2.2.1 High Throughput Signal field......Page 109
4.2.2.2 High Throughput Short Training field......Page 113
4.2.2.3 High Throughput Long Training field......Page 114
4.2.3.1 Bit string......Page 116
4.2.3.3 Stream parsing......Page 117
4.2.3.4 Interleaving......Page 118
4.2.3.5 Modulation mapping......Page 119
4.2.3.7 Transmission in 20MHz HT format......Page 120
4.2.3.8 Spatial expansion......Page 121
4.2.4 HT MF receive procedure......Page 123
4.2.4.1 RF front end......Page 124
4.2.4.3 High Throughput Signal field (HT-SIG)......Page 125
4.2.4.4 High Throughput Training fields and MIMO channel estimation......Page 126
4.2.4.5 Data field......Page 128
4.2.4.6 Demapping, deinterleaving, decoding, and descrambling......Page 129
Appendix 4.1: 20MHz basic MCS tables......Page 130
5.1 40 MHz channel......Page 133
5.1.1 40 MHz subcarrier design and spectral mask......Page 134
5.1.3 40 MHz mixed format preamble......Page 136
5.1.4 40 MHz data encoding......Page 141
5.1.4.3 Stream parsing with two encoders......Page 142
5.1.5 MCS 32: High throughput duplicate format......Page 143
5.1.7 Performance improvement with 40 MHz......Page 146
5.3 MCS enhancements: Spatial streams and code rate......Page 148
5.4 Greenfield (GF) preamble......Page 153
5.4.1 Format of the GF preamble......Page 154
5.4.3.1 Network efficiency......Page 157
5.4.3.2 Interoperability issues with legacy......Page 159
5.4.4 Preamble auto-detection......Page 161
5.5 Short guard interval......Page 163
Appendix 5.1: Channel allocation......Page 167
Appendix 5.2: 40 MHz basic MCS tables......Page 171
Appendix 5.3: Physical layer waveform parameters......Page 173
6.1 Receive diversity......Page 174
6.1.1 Maximal ratio combining basics......Page 175
6.1.2 MIMO performance improvement with receive diversity......Page 176
6.3 Space-time block coding......Page 179
6.3.1 Alamouti scheme background......Page 181
6.3.2 Additional STBC antenna configurations......Page 183
6.3.3 STBC receiver and equalization......Page 186
6.3.4 Transmission and packet encoding process with STBC......Page 188
6.4 Low density parity check codes......Page 191
6.4.1.1 Step 1: Calculating the minimum number of OFDM symbols......Page 192
6.4.1.2 Step 2: Determining the code word size and number of code words......Page 193
6.4.1.3 Step 3: Determining the number of shortening zero bits......Page 195
6.4.1.4 Step 4: Generating the parity bits......Page 196
6.4.1.5 Step 5: Packing into OFDM symbols......Page 198
6.4.2 Effective code rate......Page 202
Appendix 6.1: Parity check matrices......Page 204
Part II Medium access control layer......Page 211
7 Medium access control......Page 213
7.1 Protocol layering......Page 214
7.2.2 Scanning......Page 215
7.2.4 Association......Page 216
7.3 Distributed channel access......Page 217
7.3.1.1 SIFS......Page 218
7.3.1.2 Slot time......Page 219
7.3.1.5 Random backoff time......Page 220
7.4 Data/ACK frame exchange......Page 221
7.4.1 Fragmentation......Page 222
7.4.2 Duplicate detection......Page 223
7.5 Hidden node problem......Page 224
7.5.1.1 RTS/CTS frame exchange......Page 225
7.6 Enhanced distributed channel access......Page 226
7.6.1 Transmit opportunity......Page 228
7.6.2 Channel access timing with EDCA......Page 229
7.6.4 EIFS revisited......Page 230
7.7 Block acknowledgement......Page 231
7.7.1 Block data frame exchange......Page 233
References......Page 234
8.1.1 Throughput without MAC changes......Page 235
8.1.2 MAC throughput enhancements......Page 237
8.1.3 Throughput with MAC efficiency enhancements......Page 238
8.2 Aggregation......Page 239
8.2.1 Aggregate MSDU (A-MSDU)......Page 241
8.2.2 Aggregate MPDU (A-MPDU)......Page 242
8.2.2.2 A-MPDU length and MPDU spacing constraints......Page 243
8.3 Block acknowledgement......Page 244
8.3.2 Block ack session initiation......Page 245
8.3.4 Block ack session tear down......Page 247
8.3.6 Reorder buffer operation......Page 248
8.4.1 Normal Ack policy in an aggregate......Page 249
8.4.3.2 Motivation for partial state block ack......Page 251
8.4.3.3 Partial state block ack operation......Page 253
8.4.4 HT-immediate block ack TXOP sequences......Page 254
8.5 HT-delayed block ack......Page 255
References......Page 256
9.1.1 Establishing the CFP......Page 257
9.1.3 Data transfer during the CFP......Page 258
9.1.4 PCF limitations......Page 259
9.2.1 Traffic streams......Page 260
9.2.1.3 TS deletion......Page 261
9.2.3 Polled TXOP......Page 262
9.2.6 HCCA limitations......Page 263
9.3.1 Reverse direction frame exchange......Page 264
9.3.2 Reverse direction rules......Page 265
9.4 PSMP......Page 266
9.4.1 PSMP recovery......Page 267
9.4.2 PSMP burst......Page 268
References......Page 269
10.1.1 HT station PHY capabilities......Page 270
10.1.3 BSS capabilities......Page 271
10.2 Controlling station behavior......Page 272
10.3 20 MHz and 20/40 MHz operation......Page 273
10.3.2 20 MHz BSS operation......Page 274
10.3.3 20/40 MHz BSS operation......Page 275
10.3.3.2 20/40 MHz operation in the 2.4 GHz band......Page 276
10.3.3.3 A brief history of 40 MHz in the 2.4 GHz band......Page 277
10.3.5 Clear channel assessment in 40 MHz......Page 279
10.3.8.1 Establishing a 20/40 MHz BSS in the 5GHz bands......Page 280
10.3.8.2 Establishing a 20/40 MHz BSS in the 2.4 GHz band......Page 281
10.3.8.3 OBSS scanning during 20/40 MHz BSS operation......Page 282
10.3.8.4 Scanning requirements for 20/40 MHz stations......Page 283
10.3.10 Channel management at the AP......Page 285
10.4 A summary of fields controlling 40 MHz operation......Page 286
10.5 Phased coexistence operation (PCO)......Page 287
10.5.1 Basic operation......Page 288
10.6 Protection......Page 289
10.6.2 Protection with 802.11g or 802.11a stations present......Page 290
10.6.5 Greenfield format protection......Page 291
10.6.6 RTS/CTS protection......Page 292
10.6.8 Protection using a non-HT or HT mixed PPDU with non-HT response......Page 293
10.6.9 Non-HT station deferral with HT mixed format PPDU......Page 294
10.6.10 L-SIG TXOP protection......Page 295
References......Page 297
11.1.1.2 Type and Subtype fields......Page 298
11.1.1.5 Retry field......Page 299
11.1.1.9 Order field......Page 301
11.1.4 Sequence Control field......Page 302
11.1.5.2 Queue Size subfield......Page 303
11.1.5.4 AP PS Buffer State subfield......Page 304
11.1.6 HT Control field......Page 305
11.1.8 FCS field......Page 307
11.2.1.4 BAR......Page 308
11.2.1.6 BA......Page 310
11.2.1.8 PS-Poll......Page 312
11.2.1.10 Control Wrapper......Page 313
11.2.3 Management frames......Page 314
11.2.3.3 Association and Reassociation Response frame......Page 315
11.2.3.9 Action and Action No Ack frames......Page 316
11.3.2.1 Extended Channel Switch Announcement element......Page 320
11.3.2.2 HT Capabilities element......Page 322
11.3.2.4 20/40 BSS Coexistence element......Page 323
References......Page 334
Part III Transmit beamforming......Page 337
12 Transmit beamforming......Page 339
12.1 Singular value decomposition......Page 340
12.2 Transmit beamforming with SVD......Page 343
12.3 Eigenvalue analysis......Page 344
12.4 Unequal MCS......Page 348
12.5 Receiver design......Page 352
12.6 Channel sounding......Page 353
12.7.1 Implicit feedback......Page 355
12.7.2.1 CSI feedback......Page 360
12.7.2.2 Non-compressed beamforming weights feedback......Page 361
12.7.2.3 Compressed beamforming weights feedback......Page 362
12.8 Improved performance with transmit beamforming......Page 367
12.9 Degradations......Page 374
12.10 MAC considerations......Page 381
12.10.1 Sounding PPDUs......Page 382
12.10.2 Implicit feedback beamforming......Page 383
12.10.2.1 Calibration......Page 384
12.10.2.2 Sequences using implicit feedback......Page 386
12.10.3 Explicit feedback beamforming......Page 387
12.10.3.2 Differences between NDP and staggered sounding......Page 389
12.11 Comparison between implicit and explicit......Page 390
12.12 Fast link adaptation......Page 391
12.12.2 MCS feedback using the HT Control field......Page 393
References......Page 394
Unequal MCS for 20 MHz......Page 395
Index......Page 400
