Digital Compensation for Analog Front-Ends: A New Approach to Wireless Transceiver Design

259 Pages·2008·5.44 MB·English

by  Prof François Horlin

Digital Compensation for Analog Front-Ends
Digital C ompens ation for A nalog Front-E nds: A New Approach to Wireless Transceiver Design. FranHçooirsli n and André Bourdoux
© 2008 John Wiley & Sons, Ltd. ISBN: 978-0-470-51708-6
Digital Compensation for
Analog Front-Ends
A New Approach to Wireless
Transceiver Design
François Horlin
Université Libre de Bruxelles (ULB), Belgium
André Bourdoux
Inter-university Microelectronics Center (IMEC), Belgium
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LibraryofCongressCataloging-in-PublicationData
Horlin,François.
Digital Compensation for Analog Front-Ends: A New Approach to Wireless Transceiver Design /
FrançoisHorlin,AndréBourdoux
p.cm.
Includesbibliographicalreferencesandindex.
ISBN978-0-470-51708-6(cloth)
1.Radio–Transmitter-receivers–Designandconstruction.2.Wirelesscommunicationsystems.3.Digital
communications.I.Bourdoux,André.II.Title.
TK6561.H632008
621.3845–dc22
2008003743
BritishLibraryCataloguinginPublicationData
AcataloguerecordforthisbookisavailablefromtheBritishLibrary
ISBN978-0-470-51708-6(HB)
TypesetbySunriseSettingLtd.
PrintedandboundinGreatBritainbyAntonyRoweLtd,Chippenham,England.
Thisbookisprintedonacid-freepaper.
Contents
Preface ix
1 Introduction 1
1.1 Wirelesstransceiverfunctionaldescription . . . . . . . . . . . . . . . . . . . 1
1.2 Evolutionofthewirelesstransceiverdesign . . . . . . . . . . . . . . . . . . 3
1.2.1 Independentdesignofanalogfront-endanddigitaltransceiver . . . . 3
1.2.2 Lowcostanalogfront-end . . . . . . . . . . . . . . . . . . . . . . . 3
1.2.3 Highersystemrequirements . . . . . . . . . . . . . . . . . . . . . . 4
1.2.4 Wishforsoftwaredefinedradios . . . . . . . . . . . . . . . . . . . . 4
1.2.5 Technologyscaling . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.3 Contributionofthebook . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.3.1 Low-costanalogfront-end . . . . . . . . . . . . . . . . . . . . . . . 5
1.3.2 Integratedsystemstrategy . . . . . . . . . . . . . . . . . . . . . . . 5
1.3.3 Emergingwirelesscommunicationsystems . . . . . . . . . . . . . . 5
1.4 Organization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2 NewAirInterfaces 9
2.1 Orthogonalfrequency-divisionmultiplexing . . . . . . . . . . . . . . . . . . 9
2.2 Single-carrierwithfrequencydomainequalization. . . . . . . . . . . . . . . 13
2.3 Multi-inputmulti-outputOFDM . . . . . . . . . . . . . . . . . . . . . . . . 15
2.3.1 Space–timeblockcoding . . . . . . . . . . . . . . . . . . . . . . . . 17
2.3.2 Space-divisionmultiplexing . . . . . . . . . . . . . . . . . . . . . . 18
2.3.3 Space-divisionmultipleaccess . . . . . . . . . . . . . . . . . . . . . 21
2.4 Code-divisionmultipleaccess . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.4.1 Direct-sequencecode-divisionmultipleaccess . . . . . . . . . . . . 23
2.4.2 Multi-carriercode-divisionmultipleaccess . . . . . . . . . . . . . . 24
2.4.3 Cyclic-prefixcode-divisionmultipleaccess . . . . . . . . . . . . . . 25
2.5 Frequency-divisionmultipleaccess . . . . . . . . . . . . . . . . . . . . . . . 28
2.5.1 Orthogonalfrequency-divisionmultipleaccess . . . . . . . . . . . . 28
2.5.2 Single-carrierfrequency-divisionmultipleaccess . . . . . . . . . . . 30
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
3 RealLifeFront-Ends 37
3.1 Front-Endarchitectures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
3.1.1 Mathematicalmodeloftheidealtransmitterandreceiver . . . . . . . 38
3.1.2 Classificationofarchitectures . . . . . . . . . . . . . . . . . . . . . 39
vi CONTENTS
3.1.3 Super-heterodynearchitecturewithanalogquadrature . . . . . . . . 40
3.1.4 Super-heterodynearchitecturewithdigitalquadrature. . . . . . . . . 41
3.1.5 Directconversionarchitecture . . . . . . . . . . . . . . . . . . . . . 43
3.1.6 Low-IFarchitecture . . . . . . . . . . . . . . . . . . . . . . . . . . 44
3.1.7 MIMOFEarchitecture . . . . . . . . . . . . . . . . . . . . . . . . . 44
3.2 Constituentblocksandtheirnon-idealities . . . . . . . . . . . . . . . . . . . 44
3.2.1 Amplifiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
3.2.2 Mixersandlocaloscillators . . . . . . . . . . . . . . . . . . . . . . 45
3.2.3 A/DandD/Aconverters . . . . . . . . . . . . . . . . . . . . . . . . 46
3.3 Individualnon-idealities . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
3.3.1 Nonlinearamplifiers . . . . . . . . . . . . . . . . . . . . . . . . . . 47
3.3.2 Noiseinamplifiers(AWGN) . . . . . . . . . . . . . . . . . . . . . . 53
3.3.3 Carrierfrequencyoffset . . . . . . . . . . . . . . . . . . . . . . . . 55
3.3.4 Phasenoise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
3.3.5 IQimbalance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
3.3.6 DCoffset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
3.3.7 Quantizationnoiseandclipping . . . . . . . . . . . . . . . . . . . . 64
3.3.8 Samplingclockoffset . . . . . . . . . . . . . . . . . . . . . . . . . 65
3.3.9 Samplingjitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
4 ImpactoftheNon-IdealFront-EndsontheSystemPerformance 71
4.1 OFDMsysteminthepresenceofcarrierfrequencyoffset,sampleclockoffset
andIQimbalance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
4.1.1 Modelofthenon-idealitiesinthefrequencydomain . . . . . . . . . 73
4.1.2 Effectofcarrierfrequencyoffset . . . . . . . . . . . . . . . . . . . . 77
4.1.3 Effectofsampleclockoffset . . . . . . . . . . . . . . . . . . . . . . 80
4.1.4 EffectofIQimbalance . . . . . . . . . . . . . . . . . . . . . . . . . 82
4.1.5 Combinationofeffects . . . . . . . . . . . . . . . . . . . . . . . . . 84
4.1.6 Extensiontothefrequency-dependentIQimbalance . . . . . . . . . 86
4.2 SC-FDE system in the presence of carrier frequency offset, sample clock
offsetandIQimbalance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
4.2.1 Effectofcarrierfrequencyoffset . . . . . . . . . . . . . . . . . . . . 90
4.2.2 Effectofsampleclockoffset . . . . . . . . . . . . . . . . . . . . . . 91
4.2.3 EffectofIQimbalance . . . . . . . . . . . . . . . . . . . . . . . . . 93
4.2.4 Combinationofeffects . . . . . . . . . . . . . . . . . . . . . . . . . 95
4.3 ComparisonofthesensitivityofOFDMandSC-FDE toCFO, SCOandIQ
imbalance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
4.4 OFDMandSC-FDEsystemsinthepresenceofphasenoise. . . . . . . . . . 98
4.4.1 Systemmodel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
4.4.2 ImpactofthePN . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
4.4.3 Numericalanalysis . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
4.5 OFDMsysteminthepresenceofclipping,quantizationandnonlinearity . . . 103
4.5.1 Clipping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
4.5.2 Quantization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
4.5.3 Clippingandquantizationinfrequencyselectivechannels . . . . . . 107
CONTENTS vii
4.5.4 Spectralregrowthwithclipping . . . . . . . . . . . . . . . . . . . . 108
4.5.5 Poweramplifiernonlinearity . . . . . . . . . . . . . . . . . . . . . . 110
4.5.6 SpectralregrowthwithPAnonlinearity . . . . . . . . . . . . . . . . 111
4.6 SC-FDEsysteminthepresenceofclipping,quantizationandnonlinearity . . 112
4.6.1 Impactofquantizationandclippingatthereceiver . . . . . . . . . . 113
4.6.2 Spectralregrowthwithclippingatthetransmitter . . . . . . . . . . . 113
4.6.3 SpectralregrowthwithnonlinearPA . . . . . . . . . . . . . . . . . . 116
4.7 MIMOsystems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
4.7.1 ImpactofCFOandSCOonMIMO-OFDM . . . . . . . . . . . . . . 117
4.7.2 SensitivityofSTBCandMRCtoCFO. . . . . . . . . . . . . . . . . 120
4.7.3 Antennamismatchandthereciprocityassumption . . . . . . . . . . 122
4.8 Multi-usersystems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
4.8.1 MC-CDMAversusOFDMA . . . . . . . . . . . . . . . . . . . . . . 128
4.8.2 Userdependentnon-idealities . . . . . . . . . . . . . . . . . . . . . 131
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
5 GenericOFDMSystem 135
5.1 DefinitionofthegenericOFDMsystem . . . . . . . . . . . . . . . . . . . . 135
5.1.1 Framedescription. . . . . . . . . . . . . . . . . . . . . . . . . . . . 136
5.1.2 OFDMreceiverdescription . . . . . . . . . . . . . . . . . . . . . . 138
5.2 Burstdetection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
5.2.1 Energy-baseddetection . . . . . . . . . . . . . . . . . . . . . . . . . 141
5.2.2 Auto-correlation-baseddetection. . . . . . . . . . . . . . . . . . . . 143
5.3 AGCsetting(amplitudeestimation) . . . . . . . . . . . . . . . . . . . . . . 144
5.4 Coarsetimingestimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146
5.5 CoarseCFOestimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
5.6 Finetimingestimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
5.7 FineCFOestimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
5.8 Complexityofauto-andcross-correlation . . . . . . . . . . . . . . . . . . . 152
5.9 JointCFOandIQimbalanceacquisition . . . . . . . . . . . . . . . . . . . . 153
5.9.1 Systemmodel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154
5.9.2 Likelihoodfunctionanditssecond-orderapproximation . . . . . . . 157
5.9.3 MLestimateoftheCFOintheabsenceofIQimbalance . . . . . . . 158
5.9.4 EMalgorithmforthejointCFOandIQimbalanceestimation . . . . 159
5.9.5 Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
5.9.6 Performanceandcomplexityanalysis . . . . . . . . . . . . . . . . . 163
5.9.7 CompensationoftheCFOandIQimbalance . . . . . . . . . . . . . 168
5.10 Jointchannelandfrequency-dependentIQimbalanceestimation . . . . . . . 168
5.10.1 Systemmodel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169
5.10.2 MLchannelestimation . . . . . . . . . . . . . . . . . . . . . . . . . 170
5.10.3 Performanceandcomplexityanalysis . . . . . . . . . . . . . . . . . 171
5.10.4 Frequency-dependentIQimbalancecompensation . . . . . . . . . . 172
5.11 TrackingloopsforphasenoiseandresidualCFO/SCO . . . . . . . . . . . . 174
5.11.1 EstimationofresidualCFO/SCO . . . . . . . . . . . . . . . . . . . 174
5.11.2 CFOtrackingloop . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
5.11.3 SCOtrackingloop . . . . . . . . . . . . . . . . . . . . . . . . . . . 179
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182
viii CONTENTS
6 EmergingWirelessCommunicationSystems 185
6.1 IEEE802.11n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
6.1.1 Context . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
6.1.2 Systemdescription . . . . . . . . . . . . . . . . . . . . . . . . . . . 188
6.1.3 Mainchallengesandusualsolutions . . . . . . . . . . . . . . . . . . 194
6.1.4 Compensationofnon-reciprocity . . . . . . . . . . . . . . . . . . . 203
6.2 3GPPLong-termevolution . . . . . . . . . . . . . . . . . . . . . . . . . . . 205
6.2.1 Context . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205
6.2.2 Systemdescription . . . . . . . . . . . . . . . . . . . . . . . . . . . 207
6.2.3 Mainchallengesandusualsolutions . . . . . . . . . . . . . . . . . . 210
6.2.4 Advancedchanneltracking . . . . . . . . . . . . . . . . . . . . . . . 212
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
Appendices 225
A MMSELinearDetector 227
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228
B MLChannelEstimator 229
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230
C MatlabModelsofNon-Idealities 231
C.1 Receivernon-idealities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231
C.1.1 GlobalRXnon-idealities . . . . . . . . . . . . . . . . . . . . . . . . 231
C.1.2 Receivernoise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233
C.1.3 Carrierfrequencyoffset . . . . . . . . . . . . . . . . . . . . . . . . 234
C.1.4 Phasenoise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234
C.1.5 AGC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237
C.1.6 ReceiveIQimbalance . . . . . . . . . . . . . . . . . . . . . . . . . 237
C.1.7 Samplingclockoffset . . . . . . . . . . . . . . . . . . . . . . . . . 238
C.1.8 Clippingandquantization . . . . . . . . . . . . . . . . . . . . . . . 241
C.2 Transmitternon-idealities . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242
C.2.1 GlobalTXnon-idealities . . . . . . . . . . . . . . . . . . . . . . . . 242
C.2.2 Clippingandquantization . . . . . . . . . . . . . . . . . . . . . . . 243
C.2.3 TransmitIQimbalance . . . . . . . . . . . . . . . . . . . . . . . . . 244
C.2.4 Phasenoise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245
C.2.5 Carrierfrequencyoffset . . . . . . . . . . . . . . . . . . . . . . . . 245
C.2.6 Samplingclockoffset . . . . . . . . . . . . . . . . . . . . . . . . . 245
C.2.7 Nonlinearpoweramplifier . . . . . . . . . . . . . . . . . . . . . . . 245
D MathematicalConventions 247
E Abbreviations 249
Index 253
Preface
Thejointdesignoftheanalogfront-endandofthedigitalbasebandalgorithmshasbecome
an important field of research for a few years because it enables the wireless system and
chip designers to better trade the communication performance with the production cost.
Unfortunately the existing designs apply this approach rather opportunistically to solve a
well-determinedproblem.Thereisclearlyalackofaglobalapproach.
Theaimofthisbookistoproposeasystematicapproachtodesignadigitalcommunica-
tion system. In particular, we will present how our methodology can be applied to the
emergingwirelesscommunicationsystems.Assuch,thisbookwillbeavaluablereference
forwirelesssystemarchitectsandchipdesigners.
Moregenerally,ourbookintendstobecross-disciplinaryandtocoverindetailthedigital
compensation of many non-idealities, for a broad class of broadband emerging standards
and with a system approach in the design of the receiver algorithms. In particular, system
strategiesforjointestimationofsynchronizationandfront-endnon-idealityparameterswill
be emphasized. This approach is actually linked with the in-depth expertise that has been
developedinthewirelessresearchgroupofIMECwheretheauthorshavespentmanyyears
andhavebeeninvolvedinprojectscoveringthemainbroadbandwirelessstandards.
The organizationof the bookis also veryimportantto bringthe readerup-to-datewith
themaintopicandtoassisthim/heringraduallyabsorbingtheimportantandvastmaterial.
We cover in the first chapter a detailed introduction of the emerging wireless standards,
which is essential in understanding the rest of the book, followed in the second chapter
by a detailed descriptionof the front-endnon-idealities.Fromthis point,the readeris well
equippedtounderstandwhathappenswhenthetopicsdescribedinthefirsttwochaptersare
merged, which is the goal of the third chapter. The last two chapters continue with an in-
depthcoverageoftheestimationandcompensationalgorithms,firstforagenericsystemto
understandthemethodologyanddetailsofthesystemapproach,thenfortwomainemerging
standardstobemorepragmaticandfullyinlinewiththerealworld.
1
Introduction
1.1 Wireless transceiver functional description
Emerging wireless communication systems are carefully designed to optimize at the same
time the offered user capacity, the average spectral efficiency and the cell coverage. A
set of complementaryfunctions are successively implemented at the transmitter and at the
receiver to support the communication while still respecting the power consumption and
spectraloccupancyconstraints.Figure1.1givesafunctionaldescriptionofatypicalwireless
transceiver. Part of the functions are implemented on a digital processor (block (A) at the
transmitter and block (D) at the receiver).The other part of the functionsare implemented
in the analog front-end (block (B) at the transmitter and block (C) at the receiver). In the
following paragraphs, we give a synthetic description of the main transceiver functional
blocks.
The channel coder adds structured redundancyto the bit stream at the transmitter that
can be used at the receiver by the channel decoder to detect and ultimately correct the
bit detection errors generated by various sources of signal distortion in the system. The
interleaver/deinterleaver pair makes sure that the errorshappenat randomlocationsin the
bitstream(burstsoferrorsareavoided).
At the transmitter, the constellation mapper converts the stream of coded bits into a
stream of complex symbols. The necessary physical bandwidth is directly proportional to
the symbolrate, so that high constellation ordersare often foreseen to improvethe system
spectralefficiency.Atthereceiver,thestreamofestimatedsymbolsisconvertedbackbythe
constellationdemapperintoastreamofestimatedbits.
Mostoftheemergingcommunicationsystemsrelyontheorthogonalfrequencydivision
multiplexing (OFDM) technology (or on a derivative technology) to cope better with the
channeltimedispersion.Thestreamofcomplexsymbolsisorganizedinblocksofsymbols
(serial-to-parallel converter), that are possibly processed with the linear pre-coder and
mappedwith the carriermapper ontoa setof equallyspacedsub-carriersin the frequency
domain.TheinversefastFouriertransform(IFFT)transformstheblockstothetimedomain
andthecyclicprefix(CP)adderrepeatspartoftheresultingblockstomakethetransmitted
signalappearperiodic.Finallythetimedomainblocksofcomplexsamplesareconvertedto
Digital C ompens ation for A nalog Front-E nds: A New Approach to Wireless Transceiver Design. FranHçooirsli n and André Bourdoux
© 2008 John Wiley & Sons, Ltd. ISBN: 978-0-470-51708-6