Coping with interference in wireless networks

109 Pages·1.214 MB·English

by  Kazemitabar, Seyed Javad

SIGNALSANDCOMMUNICATIONTECHNOLOGY
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Seyed Javad Kazemitabar
Coping with Interference
in Wireless Networks
SeyedJavadKazemitabar
Dept.ofEEandCS
UniversityofCaliforniaIrvine
Irvine,CA92697-2700
USA
[email protected]
ISSN1860-4862
ISBN978-90-481-9989-1 e-ISBN978-90-481-9990-7
DOI10.1007/978-90-481-9990-7
SpringerDordrechtHeidelbergLondonNewYork
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To myparents
Preface
Inthisbookwestudytheeffectofinterferenceandmethodsofcopingwithitina
wirelessnetwork.Weapproachtheproblemfromthreedifferentperspectives.The
firstwhichinvolvesphysicallayerisamethodtocanceloutinterferenceinamulti-
accesschannel.WeconsiderJ transmitterunitseachequippedwithN transmitan-
tennasoverwirelessRayleighfadingchannels.Previously,itwasprovedthatwhen
each transmitter unit has N transmit antennas, using (J −1)N +r receive anten-
nasforanyr ≥1,thereceivercancompletelyseparatethesignalsofJ users.The
provideddiversitytoeachuserwasshowntobeNr iftheunitsemployspace-time
trellis codes even if the units transmit asynchronously. Here, we consider the case
when all units are synchronized and employ Quasi-Orthogonal Space-Time Block
Codes(N >2).ItisprovedthatinthiscaseareceiverwithJ+r−1antennas,with
r ≥1,canseparatethetransmittedsignalsofallunitsandprovideeachunitwitha
diversityorderofNr.
Basedonourinterferencecancellationtechnique,wethenofferanarrayprocess-
ing scheme which provides trade-off between diversity and spatial multiplexing.
It is shown via simulations that this array processing scheme performs better than
well-known modulation schemes, e.g. space-time block codes and BLAST, for a
moderate number of receive antennas. We then derive the diversity order of these
multipleantennamulti-usercancellationanddetectionschemes.
Inoursecondapproachweassumethephysicallayerdidnotremoveinterference
fully.Wethentrytooptimizeourmedium-accesscontrol(MAC)layer.Weconsider
the problem of joint routing, scheduling and power control in multi-hop wireless
networks.Weusealinearrelationbetweenlinkcapacityandsignaltointerference
noiseratioinourformulation.Inapreviouswork,usingadualityapproach,theop-
timallinkschedulingandpowercontrolthatminimizesthetotalaveragetransmis-
sionpowerisfound.Weformulatethisproblemasalinearprogrammingproblem
with exponential number of constraints. To cope with the exponential number of
constraints, we propose an iterative algorithm based on the cutting plane method.
The separation Oracle for the cutting plane algorithm turns out to be an element-
wiseconcaveoptimizationproblemthatcanbeeffectivelysolvedusingbranchand
boundalgorithm.
vii
viii Preface
We extend the same method to find the optimal routing scheduling and power
control.Simulationresultsshowthatthismethodologyismoreefficientandscalable
comparedtothepreviouslyproposedalgorithm.
As a third approach we investigate the connectivity of fading wireless ad-hoc
networks. We first define interference, and based on that propose a few metrics of
connectivity.Wethenstudytheeffectofinterferenceonconnectivitybasedoneach
ofthosemetrics.
SeyedJavadKazemitabar
Acknowledgements
TheworkpresentedinthisbookwasobtainedthroughmyresearchintheUniversity
ofCaliforniaIrvine.IwouldliketothankmyadvisorProfessorHamidJafarkhani
forhisguidanceduringthoseyears.
ix
Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1 CopingwithInterferenceinPhysicalLayer . . . . . . . . . . . . . 1
2 CopingwithInterferenceinMedium-AccessControl(MAC)Layer 3
3 EffectofInterferenceonConnectivity. . . . . . . . . . . . . . . . 6
2 Multi-UserCommunicationandInterferenceCancellation . . . . . . 9
1 TheChannelModel . . . . . . . . . . . . . . . . . . . . . . . . . 9
2 InterferenceCancellationUsingSpace-TimeBlockCoding . . . . 9
3 InterferenceCancellationUsingQuasi-OrthogonalSpace-Time
BlockCoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4 InterferenceCancellationUsingMinimumDecodingComplexity
Quasi-OrthogonalSpace-TimeBlockCodes(MDC-QOSTBC) . . 23
5 ApplicationoftheNewInterferenceCancellationSchemein
ArrayProcessing . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
6 SimulationResults . . . . . . . . . . . . . . . . . . . . . . . . . . 26
3 DiversityAnalysisofMultiple-AntennaMulti-UserSystems . . . . . 31
1 DiversityOrderinaCommunicationScheme . . . . . . . . . . . . 31
2 Multi-UserDetectionUsingAlamouti. . . . . . . . . . . . . . . . 32
3 Multi-UserDetectionforMorethanTwoTransmitAntennas. . . . 42
4 JointArrayProcessingandSpace-TimeCoding . . . . . . . . . . 49
5 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
AppendixA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
AppendixB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
4 Global Optimal Routing, Scheduling and Power Control for
Multi-HopWirelessNetworkswithInterference . . . . . . . . . . . . 59
1 ModelingandProblemFormulation . . . . . . . . . . . . . . . . . 59
2 PowerControl,SchedulingandRoutingAlgorithm . . . . . . . . . 63
3 Nonlinearvs.Linear . . . . . . . . . . . . . . . . . . . . . . . . . 70
4 SimulationResultsandDiscussion . . . . . . . . . . . . . . . . . 71
xi
xii Contents
5 ConnectivityinWirelessNetworks . . . . . . . . . . . . . . . . . . . 79
1 TheCapacityMetric . . . . . . . . . . . . . . . . . . . . . . . . . 79
2 TheSERMetric . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
3 CapturingTemporalCorrelationofErgodicChannels . . . . . . . 89
4 ExperimentalVerificationofAnalysis . . . . . . . . . . . . . . . . 89
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101