On MIMO Systems and Adaptive Arrays For Wireless Communication

309 Pages·2004·2.66 MB·English

Uppsala University
Signals and Systems
ON MIMO SYSTEMS AND
ADAPTIVE ARRAYS FOR
WIRELESS COMMUNICATION
Analysis and Practical Issues
Mattias Wennstro¨m
UPPSALA UNIVERSITY 2002
DissertationforthedegreeofDoctorofPhilosophy
inSignalProcessingatUppsalaUniversity,2002.
ABSTRACT
Wennstro¨m,M.,2002. OnMIMOSystemsandAdaptiveArraysforWirelessCom-
munications: Analysis and Practical Aspects, 291 pp. Uppsala. ISBN 91-506-
1619-6.
Thisthesisisconcernedwiththeuseofmultipleantennaelementsinwirelesscommunica-
tionoverfrequencynon-selectiveradiochannels.Bothmeasurementresultsandtheoretical
analysisarepresented. Newtransmitstrategiesarederivedandcomparedtoexistingtrans-
mitstrategies,suchasbeamformingandspacetimeblockcoding(STBC).Itisfoundthat
the best transmission algorithm is largely dependent on the channel characteristics, such
asthenumberoftransmitandreceiveantennasandtheexistenceofalineofsightcompo-
nent. Rayleighfadingmultipleinputmultipleoutput(MIMO)channelsarestudiedusing
an eigenvalue analysis and exact expressions for the bit error rates and outage capacities
forbeamformingandSTBCisfound.IngeneralareMIMOfadingchannelscorrelatedand
thereexistsamutualcouplingbetweenantennaelements. Thesefindingsaresupportedby
indoorMIMOmeasurements. Itisfoundthatthemutualcouplingcan,insomescenarios,
increasetheoutagecapacity. Anadaptiveantennatestbedisusedtoobtainmeasurement
resultsfortheSIMOchannel. Theresultsareanalyzedanddesignguidelinesareobtained
forhowabeamformerimplementedinhardwareshallbeconstructed. Theeffectsofnon-
lineartransmitamplifiersinarrayantennasarealsoanalyzed,anditisshownthatanarray
reduces the effective intermodulation distortion (IMD) transmitted by the array antenna
byaspatialfilteringoftheIMD.Anovelfrequencyallocationalgorithmisproposedthat
reducesIMDevenfurther. Theuseofalowcostantennawithswitchabledirectionalprop-
erties,theswitchedparasiticantenna,isstudiedinaMIMOcontextandcomparedtoarray
techniques. Itisfoundthatithascomparableperformance,atafractionofthecostforan
arrayantenna.
Keywords: antennaarray, calibration, mutualcoupling, MIMOsystem, flatfading, non-
linearamplifier,switchedparasiticantenna,analogbeamformer,adaptiveantennatestbed.
MattiasWennstro¨m,SignalsandSystems,UppsalaUniversity,POBox528,
SE-75120Uppsala,Sweden. Email: [email protected].
(cid:1)c MattiasWennstro¨m2002
ThisthesishasbeenpreparedusingLATEX.
ISBN 91-506-1619-6
PrintedinSwedenbyElandersGotabAB,Stockholm,September2002.
DistributedbySignalsandSystems,DepartmentofMaterialScience,
UppsalaUniversity,Uppsala,Sweden.
To my parents
iv
Contents
Acknowledgments ix
AbbreviationsandAcronyms xi
Notationandusedsymbols xv
1 Introduction 1
1.1 ModellingthewirelessMIMOsystem . . . . . . . . . . . . . . . 10
1.1.1 Signalmodels . . . . . . . . . . . . . . . . . . . . . . . . 10
1.1.2 Channelmodels . . . . . . . . . . . . . . . . . . . . . . . 11
1.2 Outlineandcontributionsofthisthesis . . . . . . . . . . . . . . . 18
1.2.1 MIMOsystems . . . . . . . . . . . . . . . . . . . . . . . 19
1.2.2 MeasurementsandanalysisofaSIMOsystem . . . . . . 21
1.2.3 Non-lineartransmitamplifiersinMISOsystems . . . . . 22
1.2.4 Anovelantennaconcept-Theswitchedparasiticantenna 23
1.3 Topicsforfutureresearch . . . . . . . . . . . . . . . . . . . . . . 24
2 Multiantennasystemswithgeneralflatfadingchannels 27
2.1 TheMaximumLikelihooddetectorforlinearspacetimecodes . . 28
2.2 MutualInformationandChannelCapacity . . . . . . . . . . . . . 34
2.2.1 MutualinformationwithCSIattransmitter . . . . . . . . 37
2.2.2 MutualinformationwithnoCSIatthetransmitter. . . . . 41
2.2.3 MISOandSIMOsystems . . . . . . . . . . . . . . . . . 41
2.3 CommunicationwithnoCSIatthetransmitter . . . . . . . . . . . 42
2.3.1 SpatialMultiplexing . . . . . . . . . . . . . . . . . . . . 42
2.3.2 Space-TimeCoding. . . . . . . . . . . . . . . . . . . . . 43
2.4 CommunicationwhenCSIisavailableatthetransmitter. . . . . . 46
v
vi Contents
2.4.1 Preliminaries . . . . . . . . . . . . . . . . . . . . . . . . 49
2.4.2 MaximizingspectralefficiencyatatargetBER . . . . . . 50
2.4.3 MinimizingthetotalBERatatargetspectralefficiency . . 57
2.5 Beamforming . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
2.5.1 ReceivebeamforminginSIMOChannels . . . . . . . . . 63
2.5.2 Fixedmultibeamantennas . . . . . . . . . . . . . . . . . 64
2.6 Concludingremarks . . . . . . . . . . . . . . . . . . . . . . . . . 65
2.A Derivationoftheequation(2.15)and(2.17) . . . . . . . . . . . . 68
2.B Derivationofequation(2.63)and(2.64) . . . . . . . . . . . . . . 69
2.C ProofofTheorem2.1 . . . . . . . . . . . . . . . . . . . . . . . . 72
2.D ProofofTheorem2.2 . . . . . . . . . . . . . . . . . . . . . . . . 74
3 MIMOsystemperformance 77
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
3.2 Stochasticchannelmodels . . . . . . . . . . . . . . . . . . . . . 78
3.2.1 TheNakagami-mfadingdistribution . . . . . . . . . . . . 79
3.2.2 TheRayleighandRiceanfadingdistributions . . . . . . . 80
3.3 Physicalchannelmodels . . . . . . . . . . . . . . . . . . . . . . 89
3.3.1 Scatteringdiscmodel . . . . . . . . . . . . . . . . . . . . 89
3.3.2 One-ringmodel . . . . . . . . . . . . . . . . . . . . . . . 90
3.4 MeasuredMIMOchannels . . . . . . . . . . . . . . . . . . . . . 92
3.4.1 TheMeasurementSetup . . . . . . . . . . . . . . . . . . 92
3.4.2 Coherencebandwidth. . . . . . . . . . . . . . . . . . . . 93
3.4.3 Fadingstatistics . . . . . . . . . . . . . . . . . . . . . . . 93
3.4.4 SignalCorrelation . . . . . . . . . . . . . . . . . . . . . 94
3.4.5 Eigenvalueanalysis . . . . . . . . . . . . . . . . . . . . . 96
3.4.6 Thecapacityofthemeasuredchannels . . . . . . . . . . 98
3.4.7 Thebiterrorrate . . . . . . . . . . . . . . . . . . . . . . 104
3.5 TransmissionoverfadingchannelswithoutCSIatthetransmitter . 104
3.5.1 AnalyzingorthogonalSTBCperformance . . . . . . . . . 106
3.5.2 OutagecapacityforSTBC . . . . . . . . . . . . . . . . . 109
3.5.3 ThebiterrorrateofSTBC . . . . . . . . . . . . . . . . . 109
3.5.4 Independentfadingandnomutualcoupling . . . . . . . . 110
3.5.5 Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 112
3.5.6 ConclusionsofSTBCperformanceincorrelatedNakagami
channels. . . . . . . . . . . . . . . . . . . . . . . . . . . 119
3.6 TransmissionoveraRayleighfadingchannelwithCSIatthetrans-
mitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
3.6.1 MaximizingthespectralefficiencyatatargetBER . . . . 121
3.6.2 MinimizingBERatgiventhroughput . . . . . . . . . . . 123
Contents vii
3.6.3 Beamforming . . . . . . . . . . . . . . . . . . . . . . . . 126
3.7 ImprovingSTBCwithquantizedtransmitterCSI . . . . . . . . . 132
3.7.1 Thepairwiseerrorprobability . . . . . . . . . . . . . . . 134
3.7.2 Simulationresults . . . . . . . . . . . . . . . . . . . . . 136
3.8 Concludingremarks . . . . . . . . . . . . . . . . . . . . . . . . . 140
3.A ProofofCorollary3.1andadiscussionofConjecture3.1 . . . . . 144
3.B ProofofLemma3.1 . . . . . . . . . . . . . . . . . . . . . . . . . 145
3.C ProofofCorollary3.2 . . . . . . . . . . . . . . . . . . . . . . . . 149
3.D ProofofTheorem3.2 . . . . . . . . . . . . . . . . . . . . . . . . 150
3.E ProofofTheorem3.3 . . . . . . . . . . . . . . . . . . . . . . . . 151
3.F ProofofCorollary3.3 . . . . . . . . . . . . . . . . . . . . . . . . 151
3.G ProofofTheorem3.4. . . . . . . . . . . . . . . . . . . . . . . . . 152
3.H ProofofCorollary3.4. . . . . . . . . . . . . . . . . . . . . . . . 152
3.I Table3.2inTheorem3.4. . . . . . . . . . . . . . . . . . . . . . . 153
4 MeasurementsandanalysisofaSIMOsystem 155
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
4.2 Adaptiveantennaarchitecture . . . . . . . . . . . . . . . . . . . 157
4.3 PerformanceinaLOSchannel . . . . . . . . . . . . . . . . . . . 161
4.4 Laboratorymeasurements . . . . . . . . . . . . . . . . . . . . . . 163
4.5 Outdoormeasurements . . . . . . . . . . . . . . . . . . . . . . . 167
4.5.1 Themeasurementrangesetup . . . . . . . . . . . . . . . 167
4.5.2 Measurementofradiationpatterns . . . . . . . . . . . . . 168
4.5.3 BERfromoutdoormeasurements . . . . . . . . . . . . . 173
4.6 Qualitativetestinamultipathenvironment . . . . . . . . . . . . . 175
4.7 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176
5 FiniteWeightResolutionandCalibrationIssues 179
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179
5.2 Thehardwarechannelmodel . . . . . . . . . . . . . . . . . . . . 182
5.2.1 Off-lineCalibration . . . . . . . . . . . . . . . . . . . . . 184
5.2.2 Theoutputsignalpower . . . . . . . . . . . . . . . . . . 185
5.3 Theadaptiveantennatestbed . . . . . . . . . . . . . . . . . . . . 189
5.3.1 Hardware . . . . . . . . . . . . . . . . . . . . . . . . . . 189
5.3.2 TheSMIalgorithm . . . . . . . . . . . . . . . . . . . . . 190
5.3.3 Theweighterrorvariance . . . . . . . . . . . . . . . . . 191
5.3.4 Comparisonofmeasurementsandtheory . . . . . . . . . 192
5.4 Simulationandmeasurementresults . . . . . . . . . . . . . . . . 194
5.4.1 Simulationsetup . . . . . . . . . . . . . . . . . . . . . . 194
5.4.2 Validationofsimulationmodel . . . . . . . . . . . . . . . 194
viii Contents
5.4.3 NumberofADCbits . . . . . . . . . . . . . . . . . . . . 195
5.4.4 Weightaccuracy . . . . . . . . . . . . . . . . . . . . . . 196
5.4.5 Calibrationerrors . . . . . . . . . . . . . . . . . . . . . . 197
5.5 TwoAuto-CalibrationAlgorithms . . . . . . . . . . . . . . . . . 200
5.5.1 Problemformulation . . . . . . . . . . . . . . . . . . . . 201
5.5.2 Thealgorithms . . . . . . . . . . . . . . . . . . . . . . . 203
5.5.3 Simulationstudy . . . . . . . . . . . . . . . . . . . . . . 207
5.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211
6 NonlinearitiesintransmitamplifiersforMISOsystems 213
6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213
6.2 Signalandamplifiermodels . . . . . . . . . . . . . . . . . . . . 218
6.2.1 Thefarfieldradiationpattern . . . . . . . . . . . . . . . 224
6.2.2 Measurementsofthefarfieldradiationpattern . . . . . . 227
6.3 NonlinearDistortioninSwitchedMultibeamFDMASystems . . . 229
6.3.1 UtilizingtheCombinedBeam-FrequencyScheme. . . . . 232
6.3.2 ComputerGeneratedResults . . . . . . . . . . . . . . . . 238
6.3.3 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 244
6.4 IntermodulationdistortioninaSISOcase . . . . . . . . . . . . . 246
6.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250
6.A Thesolutiontotheintegralin(6.57) . . . . . . . . . . . . . . . . 251
7 SwitchedParasiticAntennaApplicationsforWirelessSystems 253
7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253
7.2 Switchedparasiticantennas . . . . . . . . . . . . . . . . . . . . . 254
7.3 MIMOchannelcapacityanddiversitygain . . . . . . . . . . . . . 256
7.3.1 Channelcapacity . . . . . . . . . . . . . . . . . . . . . . 257
7.4 EvaluatingBERusingSTBC . . . . . . . . . . . . . . . . . . . . 260
7.5 High-ResolutionDirectionFindingUsingaSPA . . . . . . . . . . 261
7.5.1 TheSPAinaDFapplication . . . . . . . . . . . . . . . . 263
7.5.2 DirectionFindingPerformance. . . . . . . . . . . . . . . 264
7.5.3 EstimationMethods . . . . . . . . . . . . . . . . . . . . 266
7.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267
A TheButlerMatrix 269
Imaynothavegone
whereIintendedtogo,
butIthinkIhaveendedup
whereIintendedtobe.
DouglasAdams
Acknowledgments
When I first stepped onto the unpaved path of research five years ago, I had an
almostblankmapinmyhand,whereonlythelargesttracksweredrawn. Istarted
walking, and during my journey I managed to draw the map myself. Today, the
map is almost complete and I hope it can be useful for other travellers. I have
been down many frustrating sidings, but I have also found new useful paths that
leadtonewdiscoveries,whichisveryrewardingandthesourceofmymotivation.
Several individuals have played an important role in the journey that led to this
thesis. Firstofall, Iwouldliketoexpressmygratitudetomysupervisorsandco-
authors, Professor Anders Rydberg and Dr. Tommy O¨berg, for their support and
foralwaysbelievinginmycapabilities,especiallywhenIwaslostforawhile.
IamverygratefultoProfessorAndersAhle´nandProfessorMikaelSternadfor
alltheirhelpandencouragingwordsduringtheyearsandforreadingandconstruc-
tivelycriticizingthethesismanuscript.
And I especially want to acknowledge three of my co-authors during these
years: First,Tekn.Lic. JonasStrandellwithwhomIspentseveralweeksinabunker
under an airfield in Arboga, desperately trying to repair an unruly smart antenna,
it was “tra¨ligt” but fun. We also enjoyed Chinese food at the local restaurant,
every day, for weeks. Secondly, I acknowledge Dr. Erik Lindskog, who’s diurnal
rhythmalwaysissynchronizedtoaGMT-7hrSiliconValleyclock,independently
of which country he is working in. Thanks also to Dr. Thomas Svantesson, I will
never forget when we hatched the idea of using parasitic antennas during a pub
visitinBoston.
I gratefully acknowledge all my former and present colleagues at the Signals
and Systems Group for creating such a pleasant work environment and for help-
ingmetosolvemanymathematicalproblemsatthewhiteboardduringthe“fika”-
breaks. Especially the members of the Thursday club, consisting of some Ph.D.
Students at the Signals and Systems Group plus our guest researchers Carmen
Alonso and Dr. Monica Nicoli, are acknowledged. The Thursday club’s weekly
dinner endeavors at some “nation” has been a source of most welcome distrac-
tion. Especially our seemingly never-ending discussions about train movies and
ix
x Acknowledgments
thedefinitionofstrictaltruism.
Two friends have had a special impact on me during these five years. I would
like to thank Dr. Ha˚kan Engqvist who is an excellent lunch partner who gladly
discuss anything from tribology to Seinfeld episodes. Also Kristina Terenius is
thanked for spreading her energy and pushing me to keep my heart and lungs in
shapeandalsoforbeinganinvigoratingdiscussionpartner.
I also owe my thanks to my parents, Ann-Cathrin and Hans, who always en-
courageandsupportmeinallmydecisions. Youhavebeenpatient.
Finally, I would like to express my deepest gratitude and appreciation to my
fiance´eMianforherloveandpatience. Youhavebeenwithmethewholejourney.
Thank you for all support, without you this thesis would never have been com-
pleted.
MattiasWennstro¨m
Uppsala,October2002.