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

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8 Introductiona high immunity against multi-path dispersion can be provided since the useful symbolduration T s on each sub-stream is much larger than the channel time dispersion.Hence, the effects of ISI are minimized. Since the amount of filters and oscillatorsnecessary is considerable for a large number of sub-carriers, an efficient digital implementationof a special form of multi-carrier modulation, called orthogonal frequency divisionmultiplexing (OFDM), with rectangular pulse-shaping and guard time was proposed inReference [4]. OFDM can be easily realized by using the discrete Fourier transform(DFT). OFDM, having densely spaced sub-carriers with overlapping spectra of the modulatedsignals, abandons the use of steep band-pass filters to detect each sub-carrier as itis used in FDMA schemes. Therefore, it offers high spectral efficiency.Today, progress in digital technology has enabled the realization of a DFT also forlarge numbers of sub-carriers (up to several thousand), through which OFDM has gainedmuch importance. The breakthrough of OFDM came in the 1990s as it was the modulationchosen for ADSL in the USA [11] and was selected for the European DABstandard [14]. This success continued with the choice of OFDM for the European DVB-T standard [17] in 1995 and later for the WLAN standard IEEE 802.11a [32] and theinteractive terrestrial return channel (DVB-RCT) [16] as well as the European DVB-Hstandard [15]. Further deployments of OFDM technology are in the cellular mobile radiostandard 3GPP LTE and future broadband wireless access standards such as HIPERMANand IEEE 802.16x/WiMAX [19, 33, 52, 53]. Table 5 summarizes the main characteristicsof several broadcasting and WLAN standards employing OFDM.The advantages of multi-carrier modulation on the one hand and the flexibility offeredby the spread spectrum technique on the other hand have motivated many researchers toinvestigate the combination of both techniques, known as Multi-Carrier Spread Spectrum(MC-SS). This combination, published in 1993 by several authors independently [10, 13,20, 27, 37, 48, 56], has introduced new multiple access schemes called MC-CDMA andMC-DS-CDMA. It allows one to benefit from several advantages of both multi-carriermodulation and spread spectrum systems by offering, for instance, high flexibility, highspectral efficiency, simple and robust detection techniques, and narrowband interferencerejection capability.Multi-carrier modulation and multi-carrier spread spectrum are today considered potentialcandidates to fulfill the requirements of next-generation (4G) high speed wirelessmultimedia communications systems, where spectral efficiency and flexibility are consideredas the most important criteria for the choice of the air interface.Table 5Examples of wireless transmission systems employing OFDMParameter DAB DVB-T IEEE 802.11a IEEE 802.11nCarrierfrequencyVHF VHF and UHF 2.4 and 5 GHz 2.4 and 5 GHzBandwidth 1.5 MHz 8MHz (7MHz) 20 MHz 40 MHzMax. data rate 1.7 Mbit/s 31.7 Mbit/s 54 Mbit/s 248 Mbit/sNumber of 192 up to 1536 1705 and 6817 52 52 and 104sub-carriers (256 up to 2048) (2048 and 8196) (64) (64 and 128)(FFT size)
Introduction 9Multi-Carrier Spread SpectrumSince 1993, various combinations of multi-carrier modulation with the spread spectrumtechnique have been introduced as multiple access schemes. It has been shown thatmulti-carrier spread spectrum (MC-SS) offers high spectral efficiency, robustness, andflexibility [31]. Two different philosophies exist, namely MC-CDMA (or OFDM-CDMA)and MC-DS-CDMA (see Figure 4 and Table 6).MC-CDMA is based on a serial concatenation of direct sequence (DS) spreadingwith multi-carrier modulation [10, 20, 27, 56]. The high-rate DS spread data stream ofspreading code01L-1subcarrier f 0subcarrier f 1subcarrier f Nc −1MC-CDMA(Frequency diversity)spread data symbols01L-1data symbolsserialtoparallelconverterspreading code0 1L-1subcarrier f 0subcarrier f 1subcarrier f Nc −1spread data symbolsMC-DS-CDMA(Time diversity)0 1L-1Figure 4General principle of MC-CDMA and MC-DS-CDMA systemsTable 6Main characteristics of different MC-SS conceptsParameter MC-CDMA MC-DS-CDMASpreading Frequency direction Time directionSub-carrier spacing F S = P GF S ≥ P GN c T d N c T dDetection algorithmSpecific characteristicsApplicationsMRC, EGC, ZF, MMSEequalization, IC, MLDVery efficient for thesynchronous downlink by usingorthogonal codesSynchronous uplink anddownlinkCorrelation detector (coherentrake)Designed especially for anasynchronous uplinkAsynchronous uplink anddownlink
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Page 11 and 12: Contentsix4.3.2 One-Dimensional Cha
Page 13: ForewordThis book discusses multi-c
Page 17 and 18: Preface (First Edition)Nowadays, mu
Page 19: AcknowledgementsThe authors would l
Page 22 and 23: 2 Introductionambitious technologic
Page 24 and 25: 4 IntroductionTables 1 and 2 summar
Page 26 and 27: 6 IntroductionPower densityTimeFreq
Page 30 and 31: 10 Introductionprocessing gain P G
Page 32 and 33: 12 Introductionand interactive mult
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Page 36 and 37: 16 FundamentalsBSTSFigure 1-1Time-v
Page 38 and 39: 18 Fundamentalswhere p =|a p | 2 (1
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Page 42 and 43: 22 FundamentalsTable 1-2 Delay powe
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Page 46 and 47: 26 Fundamentalson sub-channel n of
Page 48 and 49: 28 Fundamentals10 010 −1OFDM (OFD
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Page 52 and 53: 32 FundamentalsThe discrete length
Page 54 and 55: 34 FundamentalsThe following matrix
Page 56 and 57: 36 FundamentalsTable 1-11Wireless l
Page 58 and 59: 38 FundamentalsFrequency hopping (F
Page 60 and 61: 40 FundamentalsFinally, a threshold
Page 62 and 63: 42 Fundamentals1.3.3 Applications o
Page 64 and 65: 44 FundamentalsTable 1-12Radio link
Page 66 and 67: 46 FundamentalsOrthogonalV-SF codeF
Page 68 and 69: {{48 Fundamentalsdata symbolsspread
Page 70 and 71: 50 FundamentalsCellular Mobile Radi
Page 72 and 73: 52 Fundamentals[27] Haindl B., “M
Page 75 and 76: 2MC-CDMA and MC-DS-CDMAIn this chap
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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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112 Hybrid Multiple Access SchemesO
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114 Hybrid Multiple Access SchemesT
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116 Hybrid Multiple Access SchemesA
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120 Hybrid Multiple Access Schemest
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122 Hybrid Multiple Access SchemesA
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126 Hybrid Multiple Access Schemes[
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4Implementation IssuesA general PHY
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Multi-Carrier Modulation and Demodu
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Synchronization 139The performance
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Synchronization 141null symbol as a
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Synchronization 143resulting SNR ca
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Synchronization 145SNR Degradation
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Synchronization 147FFTr(k)estimated
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Synchronization 149the timing error
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Synchronization 151A first simple s
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Synchronization 153Transmitted 2 re
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Channel Estimation 155Special cases
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Channel Estimation 157The mean squa
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Channel Estimation 159by the second
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Channel Estimation 161Given the nor
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Channel Estimation 163and f D, filt
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Channel Estimation 16510 010 −110
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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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