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

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118 Hybrid Multiple Access SchemesThe transmission signal x (k) is constructed by element-wise multiplication of the compressedvector s (k) with a user-dependent phase vector c (k) of length (L g + L)Q havingthe componentsc (k)l= e −j2πlk/(QL) , l = 0,...,(L g + L)Q − 1. (3.20)The element-wise multiplication of the two vectors s (k) and c (k) ensures that each useris assigned a set of sub-carriers orthogonal to the sub-carrier sets of all other users. Eachsub-carrier set contains Q sub-carriers and the number of active users is restricted toK ≤ L. (3.21)The IFDMA receiver has to perform an equalization to cope with the ISI which is presentwith IFDMA in multi-path channels. For low numbers of Q, the optimum maximumlikelihood sequence estimation can be applied with reasonable complexity whereas forhigher numbers of Q, less complex sub-optimum detection techniques such as linearequalization or decision feedback equalization are required to deal with the ISI.Due to its low PAPR, a practical application of IFDMA can be an uplink where powerefficientterminal stations are required that benefit from the quasi constant envelope andmore complex receivers that have to cope with ISI being part of the base station.3.2.4 Localized DFT-Spread OFDMLocalized DFT-spread OFDM differs from distributed DFT-spread OFDM only in themapping of the sub-carriers. While with distributed DFT-spread OFDM the sub-carriersof the users are distributed over the whole available bandwidth, with localized DFT-spreadOFDM blocks of adjacent sub-carriers are mapped to a user. Figure 3-8 illustrates thedifferences in sub-carrier mapping between both schemes.Localized DFT-spread OFDM has the advantage that flexible channel dependentscheduling in frequency can be implemented. Moreover, it is more robust to frequencyerrors between signals from different users. The disadvantage compared to distributedDFT-spread OFDM is that the frequency diversity achieved per user is reduced. Bothlocalized and distributed DFT-spread OFDM have the same low PAPR. Due to the lowPAPR and the possibility of flexible user scheduling in frequency, localized DFT-spreadOFDM has been chosen as the access technology for the uplink of LTE (see Chapter 5).The receiver for localized DFT-spread OFDM can efficiently be realized by frequencydomain equalization [5].3.3 Multi-Carrier TDMAThe combination of OFDM and TDMA is referred to as MC-TDMA or OFDM-TDMA.Due to its well understood TDMA component, MC-TDMA is part of several high ratestandards; e.g. WLAN-EEE 802.11 a/g and WLL-IEEE 802.16a/ETSI HIPERMAN [4,10, 11] (see Chapter 5).MC-TDMA transmission is done in a frame manner like in a TDMA system. One timeframe within MC-TDMA has K time slots (or bursts), each allocated to one of the K
Multi-Carrier TDMA 119DFTSubcarrierMap.IDFTGuardinterval(a) Distributed DFT-spread OFDMDFTSubcarrierMap.IDFTGuardintervalb) Localized DFT-spread OFDMsubcarrier set to 0Figure 3-8Distributed versus localized DFT-spread OFDMterminal stations. One time slot/burst consists of one or several OFDM symbols. Theallocation of time slots to the terminal stations is controlled by the base station mediumaccess controller (MAC). Multiple access interference can be avoided when ISI betweenadjacent OFDM symbols can be prevented by using a sufficiently long guard interval orwith a timing advance control mechanism.Adaptive coding and modulation is usually applied in conjunction with MC-TDMAsystems, where the coding and modulation can be easily adapted per transmitted burst.The main advantages of MC-TDMA are in guaranteeing a high peak data rate, in itsmultiplexing gain (bursty transmission), in the absence of multiple access interference, andin simple receiver structures that can be designed, for instance, by applying differentialmodulation in the frequency direction. In the case of coherent demodulation a quiterobust OFDM burst synchronization is needed, especially for the uplink. A frequencysynchronous system where the terminal station transmitter is frequency-locked to thereceived signal in the downlink or is spending a high amount of overhead transmitted perburst could remedy this problem.Besides the complex synchronization mechanism required for an OFDM system, theother disadvantage of MC-TDMA is that diversity can only be exploited by using addi-
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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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Page 91 and 92: MC-CDMA 71Thedataofthedesireduserk
Page 93 and 94: MC-CDMA 73L corresponds to the spre
Page 95 and 96: MC-CDMA 752.1.7 Combined Equalizati
Page 97 and 98: MC-CDMA 77broadcasting, WLAN, and W
Page 99 and 100: MC-CDMA 792.1.8.1 Log-Likelihood Ra
Page 101 and 102: MC-CDMA 81For coded MC-CDMA systems
Page 103 and 104: MC-CDMA 83where Q different user gr
Page 105 and 106: MC-CDMA 85Table 2-2MC-CDMA system p
Page 107 and 108: MC-CDMA 87first iteration. The opti
Page 109 and 110: MC-CDMA 8910 010 −110 −2BER10
Page 111 and 112: MC-CDMA 9110 010 −1BER10 −210
Page 113 and 114: MC-CDMA 9310 010 −110 −2BER10
Page 115 and 116: MC-DS-CDMA 95c (k) (t)f 00d (k)S/P+
Page 117 and 118: MC-DS-CDMA 97The user-specific dela
Page 119 and 120: MC-DS-CDMA 9910 010 −1BER10 −21
Page 121 and 122: References 101[7] Brüninghaus K. a
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Page 134 and 135: 114 Hybrid Multiple Access SchemesT
Page 136 and 137: 116 Hybrid Multiple Access SchemesA
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Page 146 and 147: 126 Hybrid Multiple Access Schemes[
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 and 182: Channel Estimation 161Given the nor
Page 183 and 184: Channel Estimation 163and f D, filt
Page 185 and 186: Channel Estimation 16510 010 −110
Page 187 and 188: Channel Estimation 16710 010 −13
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Channel Estimation 169in order to r
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Channel Estimation 17110 010 −1BU
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Channel Estimation 173timefreq. 00
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Channel Coding and Decoding 1754.4.
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Channel Coding and Decoding 177Tabl
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Channel Coding and Decoding 179a (k
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Channel Coding and Decoding 181n rk
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Channel Coding and Decoding 183Bit
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Channel Coding and Decoding 185Bit
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Signal Constellation, Mapping, De-M
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Signal Constellation, Mapping, De-M
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Adaptive Techniques in Multi-Carrie
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RF Issues 193hence reduce, for inst
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RF Issues 195s(t)r(t)e jf(t)White n
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RF Issues 197receivedsignalto detec
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RF Issues 1994.7.2.1 Effects of Non
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RF Issues 2011e−011e−02UplinkDo
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RF Issues 203of data pre-distortion
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RF Issues 205Table 4-8Minimum total
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RF Issues 207Detection strategyIn t
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RF Issues 209above formula becomes(
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References 211[21] Fazel K., “Nar
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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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