Multi-Carrier and Spread Spectrum Systems: From OFDM and MC ...

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162 Implementation Issues4.3.4.4 Complexity and Performance AspectsA simple alternative to optimum Wiener filtering is a DFT-based channel estimator illustratedin Figure 4-22. The channel is first estimated in the frequency domain on the N pilotsub-carriers where pilots have been transmitted. In the next step, this N pilot estimates aretransformed with a N pilot point IDFT in the time domain and the resulting time sequencecan be weighted before it is transformed back in the frequency domain with an N c pointDFT. As long as N pilot
Channel Estimation 163and f D, filter = 333.3 Hz, where f D, filter corresponds to a velocity of v = 200 km/h. Abalanced design with approximately two-times oversampling is given with a pilot symbolspacing of N f = 6 in the frequency direction and of N t = 3 in the time direction.The resulting system parameters are summarized in Table 4-1. The chosen OFDM framestructure for pilot symbol aided channel estimation in two dimensions is illustrated inFigure 4-23.In the time direction, the last OFDM symbol with pilot symbols of the previous OFDMframe can be used for filtering. With a pilot spacing of 6 in the frequency direction,while starting and ending with a sub-carrier containing pilot symbols, a number of 511used sub-carriers per OFDM symbol is obtained and is considered in the following. Theresulting overhead due to pilot symbols is 5.6 %. With pilot symbols and data symbolshaving the same average energy, the loss in SNR V pilot due to pilot symbols is only0.3 dB for the defined multi-carrier scenario.The performance criterion for the evaluation of the channel estimation is the meansquare error, which is averaged over an OFDM frame. Thus, edge effects are also takeninto account. The information about the variance σ 2 required for the calculation of theautocorrelation matrix is assumed to be known perfectly at the receiver unless otherwisestated. In practice, the variance σ 2 can be estimated by transmitting a null symbol withoutsignal energy at the beginning of each OFDM frame (see Section 4.2.1). Alternatively,the auto-correlation function can be optimized for the highest σ 2 at which successful datatransmission should be possible.The mean square error of two-dimensional (2-D) filtering without model mismatchand two cascaded one-dimensional (2 × 1-D) filtering applied in a multi-carrier system ispresented and compared in the following. The mobile radio channel used has a uniformdelay power spectrum with τ max = 20 µs and a uniform Doppler power density spectrumwith f D,max = 333.3Hz.timefreq. 00 23data symbolpilot symboldata symbol of previous OFDMframe510pilot symbol of previous OFDMframe; used for channel estimationof actual OFDM frameT fr = 6.6 msFigure 4-23OFDM frame with pilot grid for channel estimation in two dimensions
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Multi-Carrier andSpread SpectrumSys
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This edition first published 2008©
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Contentsix4.3.2 One-Dimensional Cha
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ForewordThis book discusses multi-c
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Preface (First Edition)Nowadays, mu
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AcknowledgementsThe authors would l
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2 Introductionambitious technologic
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4 IntroductionTables 1 and 2 summar
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6 IntroductionPower densityTimeFreq
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8 Introductiona high immunity again
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10 Introductionprocessing gain P G
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12 Introductionand interactive mult
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14 Introduction[43] Saltzberg, B. R
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16 FundamentalsBSTSFigure 1-1Time-v
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18 Fundamentalswhere p =|a p | 2 (1
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20 Fundamentalssuch that the effect
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22 FundamentalsTable 1-2 Delay powe
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24 Fundamentals(i) Fixed Positioned
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26 Fundamentalson sub-channel n of
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28 Fundamentals10 010 −1OFDM (OFD
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30 Fundamentalsin order to achieve
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32 FundamentalsThe discrete length
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34 FundamentalsThe following matrix
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36 FundamentalsTable 1-11Wireless l
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38 FundamentalsFrequency hopping (F
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40 FundamentalsFinally, a threshold
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42 Fundamentals1.3.3 Applications o
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44 FundamentalsTable 1-12Radio link
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46 FundamentalsOrthogonalV-SF codeF
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{{48 Fundamentalsdata symbolsspread
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50 FundamentalsCellular Mobile Radi
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52 Fundamentals[27] Haindl B., “M
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2MC-CDMA and MC-DS-CDMAIn this chap
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MC-CDMA 57whered = (d (0) ,d (1) ,.
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MC-CDMA 59i.e. the spreading is per
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MC-CDMA 61Table 2-1 PAPR bounds of
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MC-CDMA 632.1.4.4 Rotated Constella
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MC-CDMA 65After inverse OFDM the re
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MC-CDMA 67and requires only informa
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MC-CDMA 69hard interference evaluat
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MC-CDMA 71Thedataofthedesireduserk
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MC-CDMA 73L corresponds to the spre
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MC-CDMA 752.1.7 Combined Equalizati
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MC-CDMA 77broadcasting, WLAN, and W
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MC-CDMA 792.1.8.1 Log-Likelihood Ra
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MC-CDMA 81For coded MC-CDMA systems
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MC-CDMA 83where Q different user gr
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MC-CDMA 85Table 2-2MC-CDMA system p
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MC-CDMA 87first iteration. The opti
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MC-CDMA 8910 010 −110 −2BER10
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MC-CDMA 9110 010 −1BER10 −210
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MC-CDMA 9310 010 −110 −2BER10
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MC-DS-CDMA 95c (k) (t)f 00d (k)S/P+
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MC-DS-CDMA 97The user-specific dela
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MC-DS-CDMA 9910 010 −1BER10 −21
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References 101[7] Brüninghaus K. a
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References 103[49] Steiner B., “U
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106 Hybrid Multiple Access SchemesI
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108 Hybrid Multiple Access Schemesw
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110 Hybrid Multiple Access Schemest
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Page 149 and 150: 4Implementation IssuesA general PHY
Page 151 and 152: Multi-Carrier Modulation and Demodu
Page 159 and 160: Synchronization 139The performance
Page 161 and 162: Synchronization 141null symbol as a
Page 163 and 164: Synchronization 143resulting SNR ca
Page 165 and 166: Synchronization 145SNR Degradation
Page 167 and 168: Synchronization 147FFTr(k)estimated
Page 169 and 170: Synchronization 149the timing error
Page 171 and 172: Synchronization 151A first simple s
Page 173 and 174: Synchronization 153Transmitted 2 re
Page 175 and 176: Channel Estimation 155Special cases
Page 177 and 178: Channel Estimation 157The mean squa
Page 179 and 180: Channel Estimation 159by the second
Page 181: Channel Estimation 161Given the nor
Page 185 and 186: Channel Estimation 16510 010 −110
Page 187 and 188: Channel Estimation 16710 010 −13
Page 189 and 190: Channel Estimation 169in order to r
Page 191 and 192: Channel Estimation 17110 010 −1BU
Page 193 and 194: Channel Estimation 173timefreq. 00
Page 195 and 196: Channel Coding and Decoding 1754.4.
Page 197 and 198: Channel Coding and Decoding 177Tabl
Page 199 and 200: Channel Coding and Decoding 179a (k
Page 201 and 202: Channel Coding and Decoding 181n rk
Page 203 and 204: Channel Coding and Decoding 183Bit
Page 205 and 206: Channel Coding and Decoding 185Bit
Page 207 and 208: Signal Constellation, Mapping, De-M
Page 209 and 210: Signal Constellation, Mapping, De-M
Page 211 and 212: Adaptive Techniques in Multi-Carrie
Page 213 and 214: RF Issues 193hence reduce, for inst
Page 215 and 216: RF Issues 195s(t)r(t)e jf(t)White n
Page 217 and 218: RF Issues 197receivedsignalto detec
Page 219 and 220: RF Issues 1994.7.2.1 Effects of Non
Page 221 and 222: RF Issues 2011e−011e−02UplinkDo
Page 223 and 224: RF Issues 203of data pre-distortion
Page 225 and 226: RF Issues 205Table 4-8Minimum total
Page 227 and 228: RF Issues 207Detection strategyIn t
Page 229 and 230: RF Issues 209above formula becomes(
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References 213[66] Nobilet S., Hela
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5Applications5.1 IntroductionThe de
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Introduction 217high speed as well
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3GPP Long Term Evolution (LTE) 219H
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3GPP Long Term Evolution (LTE) 221U
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3GPP Long Term Evolution (LTE) 2231
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3GPP Long Term Evolution (LTE) 227T
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3GPP Long Term Evolution (LTE) 229C
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WiMAX 237Table 5-12 Downlink LTE sp
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WiMAX 239Wi-FiBusinessTSWiMAX BSTSM
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WiMAX 241Table 5-16Summary of the I
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WiMAX 243WiMAXInteroperabilityInter
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WiMAX 245UNIAirinterfaceSNITerminal
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WiMAX 247Radio ResourceControlIniti
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WiMAX 249Frame n−1 Frame n Frame
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WiMAX 251Read RF-Channel ListScan F
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WiMAX 253NormaloperationTS measures
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WiMAX 255Table 5-18Example of some
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WiMAX 257Total bandwidth (between 1
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WiMAX 259Sub-carriers (frequency)n0
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ApplicationsWiMAX 261Table 5-23 Gen
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WiMAX 263Table 5-27(OFDMA)FEC codin
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WiMAX 265M-QAMMappingSTC withSpatia
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WiMAX 267Frame n−1 Frame n Frame
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WiMAX 269Table 5-29WirelessMAN-OFDM
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WiMAX 2710Power density in dB−25
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WiMAX 273Table 5-37diversityPeak da
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WiMAX 275Table 5-41DL link budget e
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Future Mobile Communications Concep
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Wireless Local Area Networks 283MTB
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Wireless Local Area Networks 285fre
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Interaction Channel for DVB-T: DVB-
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References 297Table 5-58Parameters
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References 299[32] Taoka H., Higuch
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302 Additional Techniques for Capac
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340 Definitions, Abbreviations, and
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350 SymbolsG l,lGG [j]h(t)h(τ,t)H(
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Index3GPP 218Adaptive techniques 19
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Index 355Forward error correction (
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Index 357Multi-carrier modulation a
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Index 359Maximum likelihood paramet
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