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### Summary

### Summary

A study of OFDM, including a comparison with other forms of single carrier modulation methods. It provides the design guidelines needed to maximise benefits from this technology. There is practical advice on how to plan, design and use OFDM to make wireless multimedia communications happen. It offers a solid base for assessing the performance of wireless OFDM systems; explains how OFDM signals are formed using the Inverse Fast Fourier Transform, how the cyclic extension mitigates the effects of modulation, and how windowing can limit out-of-band radiation; discusses the sensitivity of OFDM to synchronization errors; examines the basics of direct sequence and frequency hopping CMDA, helpful in understanding combinations of OFDM and CDMA; explains Multicarrier CDMA, various transmitter architectures, and the pros and cons compared to other CDMA techniques; and includes a discussion of the combination of OFDM and frequency hopping CDMA to get a multiple access system with similar advantages to direct sequence CDMA.

### Author Notes

Richard D. J. van Nee received his Ph.D. in Electrical Engineering from Delft University, and his M.Sc. in Electrical Engineering from Twente University.

He is a member of the technical staff at Lucent Technologies/Bell Labs in the Netherlands. Dr. van Nee was among those who proposed the OFDM-based physical layer, which was selected for standardization in IEEE 802.11, MMAC, and ETSI HiperLAN.

050

### Table of Contents

Preface | p. xiii |

Acknowledgments | p. xvii |

Chapter 1 Introduction | p. 1 |

1.1 Standardization and Frequency Bands | p. 4 |

1.2 Multimedia Communications | p. 7 |

1.2.1 The Need for High Data Rates | p. 8 |

1.2.2 Services and Applications | p. 9 |

1.2.3 Antennas and Batteries | p. 9 |

1.2.4 Safety Considerations | p. 10 |

1.2.5 ATM-Based Wireless (Mobile) Broadband Multimedia Systems | p. 12 |

1.3 Multipath Propagation | p. 15 |

1.3.1 Multipath Channel Models | p. 16 |

1.3.2 Delay Spread Values | p. 17 |

1.4 Time Variation of the Channel | p. 19 |

1.5 History of OFDM | p. 20 |

1.6 Preview of the Book | p. 24 |

References | p. 25 |

Chapter 2 OFDM Basics | p. 33 |

2.1 Introduction | p. 33 |

2.2 Generation of Subcarriers using the IFFT | p. 33 |

2.3 Guard Time and Cyclic Extension | p. 39 |

2.4 Windowing | p. 42 |

2.5 Choice of OFDM Parameters | p. 46 |

2.6 OFDM Signal Processing | p. 47 |

2.7 Implementation Complexity of OFDM Versus Single Carrier Modulation | p. 48 |

References | p. 51 |

Chapter 3 Coding and Modulation | p. 53 |

3.1 Introduction | p. 53 |

3.2 Forward Error Correction Coding | p. 54 |

3.2.1 Block Codes | p. 54 |

3.2.2 Convolutional Codes | p. 55 |

3.2.3 Concatenated Codes | p. 58 |

3.3 Interleaving | p. 59 |

3.4 Quadrature Amplitude Modulation | p. 60 |

3.5 Coded Modulation | p. 62 |

References | p. 70 |

Chapter 4 Synchronization | p. 73 |

4.1 Introduction | p. 73 |

4.2 Sensitivity to Phase Noise | p. 74 |

4.3 Sensitivity to Frequency Offset | p. 77 |

4.4 Sensitivity to Timing Errors | p. 78 |

4.5 Synchronization using the Cyclic Extension | p. 80 |

4.6 Synchronization using Special Training Symbols | p. 86 |

4.7 Optimum Timing in the Presence of Multipat | p. 88 |

References | p. 92 |

Chapter 5 Coherent and Differential Detection | p. 95 |

5.1 Introduction | p. 95 |

5.2 Coherent Detection | p. 95 |

5.2.1 Two Dimensional Channel Estimators | p. 96 |

5.2.2 One Dimensional Channel Estimators | p. 103 |

5.2.3 Special Training Symbols | p. 104 |

5.2.4 Decision Directed Channel Estimation | p. 106 |

5.3 Differential Detection | p. 107 |

5.3.1 Differential Detection in the Time Domain | p. 107 |

5.3.2 Differential Detection in the Frequency Domain | p. 112 |

5.3.3 Differential Amplitude and Phase Shift Keying | p. 115 |

References | p. 117 |

Chapter 6 The Peak Power Problem | p. 119 |

6.1 Introduction | p. 119 |

6.2 Distribution of the Peak-to-Average Power Ratio | p. 120 |

6.3 Clipping and Peak Windowing | p. 123 |

6.3.1 Required Backoff with a Non-Ideal Power Amplifier | p. 127 |

6.3.2 Coding and Scrambling | p. 130 |

6.4 Peak Cancellation | p. 131 |

6.5 PAP Reduction Codes | p. 138 |

6.5.1 Generating Complementary Codes | p. 141 |

6.5.2 Minimum Distance of Complementary Codes | p. 144 |

6.5.3 Maximum Likelihood Decoding of Complementary Codes | p. 145 |

6.5.4 Suboptimum Decoding of Complementary Codes | p. 147 |

6.5.5 Large Code Lengths | p. 150 |

6.6 SYMBOL Scrambling | p. 150 |

References | p. 153 |

Chapter 7 Basics of CDMA | p. 155 |

7.1 Introduction | p. 155 |

7.2 CDMA: Past, Present, and Future | p. 156 |

7.3 CDMA Concepts | p. 157 |

7.3.1 Pure CDMA | p. 161 |

7.4 Basic DS-CDMA Elements | p. 171 |

7.4.1 RAKE Receiver | p. 171 |

7.4.2 Power Control | p. 172 |

7.4.3 Soft Handover | p. 173 |

7.4.4 Interfrequency Handover | p. 175 |

7.4.5 Multiuser Detection | p. 175 |

References | p. 176 |

Chapter 8 Multi - Carrier CDMA | p. 179 |

8.1 Introduction | p. 179 |

8.2 Channel Model | p. 180 |

8.3 DS-CDMA and MC-CDMA Systems | p. 182 |

8.3.1 DS-CDMA System | p. 182 |

8.3.2 MC-CDMA System | p. 185 |

8.4 MC-CDMA System Design | p. 189 |

8.5 BEP LOWER Bound | p. 194 |

8.5.1 DS-CDMA System | p. 194 |

8.5.2 MC-CDMA System | p. 195 |

8.5.3 BEP Lower Bound Equivalence | p. 196 |

8.6 Numerical Results | p. 197 |

8.6.1 MC-CDMA System Design | p. 197 |

8.6.2 Down - Link BEP Performance | p. 199 |

8.6.3 Up - Link BER Performance | p. 203 |

8.7 Conclusions | p. 206 |

Appendix 8A | p. 208 |

References | p. 209 |

Chapter 9 Orthogonal Frequency Division Multiple Access | p. 213 |

9.1 Introduction | p. 213 |

9.2 Frequency Hopping OFDMA | p. 213 |

9.3 Differences between OFDMA and MC-CDMA | p. 215 |

9.4 OFDMA System Description | p. 217 |

9.4.1 Channel Coding | p. 220 |

9.4.2 Modulation | p. 220 |

9.4.3 Time and Frequency Synchronization | p. 221 |

9.4.4 Initial Modulation Timing Synchronization | p. 221 |

9.4.5 Initial Frequency Offset Synchronization | p. 222 |

9.4.6 Synchronization Accuracy | p. 222 |

9.4.7 Power Control | p. 223 |

9.4.8 Random Frequency Hopping Operation | p. 224 |

9.4.9 Dynamic Channel Allocation (Fast DCA) | p. 225 |

9.4.10 Dynamic Channel Allocation (Simple DCA) | p. 227 |

9.4.11 Capacity of OFDMA | p. 227 |

9.5 Conclusions | p. 227 |

References | p. 228 |

Chapter 10 Applications of OFDM | p. 229 |

10.1 Introduction | p. 229 |

10.2 Digital Audio Broadcasting | p. 229 |

10.3 Terrestrial Digital Video Broadcasting | p. 231 |

10.4 Magic WAND | p. 233 |

10.4.1 Magic WAND Physical Layer | p. 234 |

10.4.2 Coding | p. 236 |

10.4.3 Simulated Error Probabilities | p. 236 |

10.4.4 Effects of Clipping | p. 237 |

10.4.5 Magic WAND Medium Access Control Layer | p. 238 |

10.5 IEEE 802.11, HIPERLAN/2, and MMAC Wireless LAN Standards | p. 241 |

10.5.1 OFDM Parameters | p. 243 |

10.5.2 Channelization | p. 244 |

10.5.3 OFDM Signal Processing | p. 245 |

10.5.4 Training | p. 246 |

10.5.5 Differences between IEEE 802.11, HIPERLAN/2 and MMAC | p. 249 |

10.5.6 Simulation Results | p. 250 |

References | p. 252 |

About the Authors | p. 255 |

Index | p. 257 |