Table Of ContentWireless Networks
Wei Song
Peijian Ju
A-Long Jin
Protocol Design
and Analysis
for Cooperative
Wireless
Networks
Wireless Networks
SeriesEditor
XueminShermanShen
UniversityofWaterloo,Waterloo,Ontario,Canada
Moreinformationaboutthisseriesathttp://www.springer.com/series/14180
Wei Song • Peijian Ju (cid:129) A-Long Jin
Protocol Design and Analysis
for Cooperative Wireless
Networks
123
WeiSong PeijianJu
FacultyofComputerScience IBMCanada
UniversityofNewBrunswick Fredericton,NB,Canada
Fredericton,NB,Canada
A-LongJin
UniversityofWaterloo
Waterloo,ON,Canada
ISSN2366-1186 ISSN2366-1445 (electronic)
WirelessNetworks
ISBN978-3-319-47725-1 ISBN978-3-319-47726-8 (eBook)
DOI10.1007/978-3-319-47726-8
LibraryofCongressControlNumber:2016954727
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Preface
Cooperativewirelessnetworkshaveemergedasapromisingtechnologythatallows
wirelessdevicestotakeadvantageofdiversityandthebroadcastnatureofwireless
medium. Nonetheless, some important issues remain to be addressed to enable
practical implementation. In particular, with the fast-growing mobile traffic and
rising energy costs, energy saving needs to be taken into account in the design
of cooperative protocols. In addition, many designs and analyses assume that
the locations of cooperative wireless nodes are deterministic or known a priori.
However, due to user mobility and/or network dynamics, the node locations are
spatially random. Hence, this feature should be properly incorporated into the
protocoldesignandanalysisforcooperativewirelessnetworks.
In this book brief, we focus on the design and analysis of protocols for
cooperative wireless networks, especially, at the medium access control (MAC)
layer and cross-layer design between the MAC layer and the physical layer. It
first provides a comprehensive review of existing studies in the literature and
points out the problems that are worth further investigation. Then, it introduces
severalnovelsolutionsforcooperativewirelessnetworkprotocols,aimingtoreduce
energy consumption and address spatial random distribution of wireless nodes.
For each solution, it gives a clear system model and problem formulation, details
of the proposed cooperative schemes, comprehensive performance analysis, and
extensive numerical and simulation results that validate the analysis and examine
the performance under various conditions. At the end of this book brief, we
also highlight several interesting directions on cooperative wireless networks that
deservefutureexploration.
Fredericton,Canada WeiSong
Fredericton,Canada PeijianJu
Waterloo,Canada A-LongJin
v
Contents
1 Introduction .................................................................. 1
1.1 Motivations.............................................................. 1
1.2 Challenges............................................................... 2
1.2.1 EnergySavingwithSpatiallyRandomRelays................ 2
1.2.2 CooperativeDiversitywithMultipleRelays .................. 2
1.3 Outline................................................................... 3
References..................................................................... 4
2 RelatedWorksonCooperativeWirelessNetworks ...................... 7
2.1 CooperativeCommunications.......................................... 7
2.2 CooperationScenarios.................................................. 9
2.3 ThreeCategoriesofCooperativeMACProtocols..................... 12
2.3.1 Category-I....................................................... 13
2.3.2 Category-II...................................................... 15
2.3.3 Category-III..................................................... 17
2.4 ResearchIssuesforMAC-LayerCooperation......................... 19
2.4.1 NewCategories................................................. 19
2.4.2 CooperativeDiversity .......................................... 20
2.4.3 UserMobility ................................................... 21
2.4.4 EnergySaving................................................... 22
References..................................................................... 23
3 Energy-EfficientUncoordinatedCooperativeMACwith
UncertainRelayDistributionIntensity.................................... 27
3.1 MotivationandOverview............................................... 27
3.2 SystemModelandProblemFormulation.............................. 28
3.2.1 SystemModel................................................... 28
3.2.2 ProblemFormulation........................................... 31
3.3 RelayIntensityEstimation.............................................. 32
3.4 Energy-EfficientCooperativeSchemeandItsAnalysis............... 37
3.4.1 AnEnergy-EfficientCooperativeScheme..................... 37
3.4.2 AnalysisofCollisionProbability .............................. 41
vii
viii Contents
3.5 NumericalandSimulationResults..................................... 43
3.5.1 RelayIntensityEstimation ..................................... 43
3.5.2 EnergySavingStrategy......................................... 44
3.5.3 PerformanceEvaluation........................................ 46
3.6 Summary ................................................................ 49
AppendixA:ExtendedProofofLemma3.2withN Relays................ 49
AppendixB:Proofof(3.34)and(3.35)...................................... 50
References..................................................................... 51
4 Energy-Aware Cooperative MAC with Uncoordinated
GroupRelays................................................................. 53
4.1 MotivationandOverview............................................... 53
4.2 SystemModelandProblemFormulation.............................. 54
4.2.1 SystemModel................................................... 54
4.2.2 ProblemFormulation........................................... 56
4.3 Energy-AwareCooperationStrategy................................... 57
4.3.1 CooperationCriteria............................................ 57
4.3.2 DistributedCooperationStrategy.............................. 58
4.4 PerformanceAnalysis................................................... 60
4.4.1 UpperBoundofCollisionProbability......................... 60
4.4.2 LowerBoundofTransmissionSuccessProbability........... 63
4.4.3 UpperBoundofTransmissionSuccessProbability........... 64
4.5 NumericalandSimulationResults..................................... 65
4.5.1 TransmissionSuccessProbability.............................. 67
4.5.2 AverageDelayandDelayOutageProbability................. 67
4.5.3 EnergySavingandEnergyBalance............................ 69
4.5.4 Scalability....................................................... 71
4.6 Summary ................................................................ 73
AppendixA:Proofof(4.17).................................................. 73
AppendixB:Proofof(4.25).................................................. 74
References..................................................................... 75
5 OpportunisticCooperativeRelayingwithBackoff-Based
Contention.................................................................... 77
5.1 MotivationandOverview............................................... 77
5.2 SystemModel........................................................... 78
5.3 CooperativeRelayingStrategies ....................................... 80
5.3.1 Inter-GroupBackoff-BasedContention ....................... 81
5.3.2 Intra-GroupContention......................................... 81
5.4 PerformanceAnalysis................................................... 83
5.4.1 ProbabilityDistributionsofSpatialRandomRelays.......... 84
5.4.2 PerformanceofTwo-LevelBackoff-BasedStrategy.......... 86
5.4.3 PerformanceofHybridRelayingStrategy..................... 89
5.5 NumericalResultsandDiscussions.................................... 90
5.5.1 CDFofTransmissionSuccessProbability .................... 91
5.5.2 PerformanceUpperandLowerBounds ....................... 93
Contents ix
5.5.3 RelaySuccessProbability...................................... 94
5.5.4 BackoffDelayofRelaySelection.............................. 98
5.6 Summary ................................................................ 100
Appendix:CalculationoftheCDFF(cid:2);l.x/of(cid:2)RD;l.......................... 101
References..................................................................... 103
6 DiversityRelayingwithSpatiallyRandomMobileRelays.............. 105
6.1 MotivationandOverview............................................... 105
6.2 SystemModel........................................................... 107
6.2.1 ChannelModel.................................................. 107
6.2.2 MobilityModelandPoissonPointProcess ................... 108
6.2.3 DistributedCooperativeTransmission......................... 108
6.2.4 MACforMulti-HelperCoordination.......................... 109
6.2.5 MRCandUpperBoundofTotalSNR......................... 111
6.3 UnconditionalSuccessProbabilityandDelay......................... 112
6.3.1 ExactUnconditionalPDFofSNRUpperBound ............. 112
6.3.2 ApproximateUnconditionalPDFofSNRUpperBound..... 114
6.3.3 ApproximationofUnconditionalSuccessProbability........ 115
6.3.4 DelayAnalysisofMACCoordinationSchemes.............. 116
6.3.5 Outage-DelayTradeoff......................................... 118
6.4 NumericalandSimulationResults..................................... 119
6.4.1 AnalysisValidation............................................. 120
6.4.2 Outage-DelayTradeoff......................................... 123
6.5 Summary ................................................................ 124
Appendix:ProofofLemma6.1............................................... 125
References..................................................................... 126
7 ConclusionsandFutureDirections ........................................ 129
7.1 Conclusions ............................................................. 129
7.2 FutureWork............................................................. 130
Chapter 1
Introduction
1.1 Motivations
Inthepastdecade,wirelessnetworkshavebeenwidelystudiedandused.However,
wirelesscommunicationsfaceseveralchallengingissueswhicharenotimposedin
wirednetworks,suchasmobility,powerconsumption,interferenceandreliability.
Besides, signal fading is often a problem in wireless networks, which is caused
bymultipathpropagation andshadowing. Todeal withthesechallenges, attractive
techniques, such as multiple input and multiple output (MIMO) and coopera-
tive communications [4, 7], have been developed by exploiting spatial diversity.
Nonetheless, due to the size, cost and energy limitations of mobile devices, it can
be infeasible to deploy multiple antennas in some wireless terminals. In order to
meet the needs of future wireless networks, user cooperation [13] is studied as a
promising low-cost technique to provide spatial diversity. Taking advantage of the
inherentbroadcastingnatureofthewirelessmedium,thenodeswithgoodchannel
conditions can forward the overheard data to facilitate the transmission between
source(S)anddestination(D).
Originally, most of the research works focus on the physical layer cooperation
[4, 7], where the cooperative schemes pay more attention to the various methods
of signal processing at the relay node and signal combination at the destination
node. With physical layer cooperation, either diversity or multiplexing can be
achieved,whichimprovesthequalityofcommunicationsintheupperlayers.Since
multiple cooperative nodes are available during packet transmission, it is vital to
coordinatethesenodestoaccessthechannelinacooperativefashion.Toachievethe
cooperationgainatupperlayers,considerableresearchattentionhasbeenattracted
to the medium access control (MAC) layer [6, 9]. Different from physical layer
cooperation, MAC layer cooperation needs to figure out when to cooperate and
whomtocooperatewith.
Whilecentralizedsolutions[2,5,6]canrelyonacentralcontrollertodetermine
the best relays, distributed solutions also attract considerable research attention
©SpringerInternationalPublishingAG2017 1
W.Songetal.,ProtocolDesignandAnalysisforCooperativeWirelessNetworks,
WirelessNetworks,DOI10.1007/978-3-319-47726-8_1
2 1 Introduction
duetolightweightsignalingandgoodscalability.Intheprobability-basedschemes
[10–12], each relay that successfully overhears the data from the source indepen-
dently determines a forwarding probability by synthesizing a variety of factors. In
thebackoff-basedschemes[1,8],eachrelaymakesuseoflocalinformationtotune
abackofftimesothatabestrelaywithasmallestbackofftimewinsthecontention
toforwardtheoverhearddata.AlthoughcooperativeMAChasbeenwidelystudied,
manypracticalissuesremaintobeaddressed.
1.2 Challenges
1.2.1 EnergySavingwithSpatiallyRandomRelays
Withrisingenergycostsandrigorousenvironmentalstandards,greencommunica-
tionsbecomeanewresearchtrendinrecentyears,especially,toaccommodatethe
fast-growing multimedia services in wireless networks, since mobile devices are
usuallyenergy-constrained.Hence,howtoreduceenergyconsumptionisacritical
issue for MAC layer cooperation. Besides, many existing works assume that the
networktopologyisknownapriori[10]andfocusonthethroughputperspective[6].
It is vital to relax the assumption of deterministic known topology and take into
accountrelayingnodesthatarerandomlydistributedinaspatialarea.
1.2.2 CooperativeDiversitywith MultipleRelays
AsmotivatedbydiversityandMIMO,cooperativerelaylinksandthedirectlinkcan
beusedtotransmitthesamepackettoachievediversity.Akeyproblemistochoose
a good criterion to start cooperation. Cross-layer techniques can be employed to
dynamicallyestimatethechannelcondition.Ifatransmissionfailureisverylikely
to happen with a poor direct link condition, cooperative diversity transmission is
initiatedtosatisfycertainQoSrequirements[2].Whetherthesourceshouldalways
enablediversitytransmissionoronlyactivateitondemanddependsonfactorssuch
astheenergyconsumptionandavailabilityofhelpers.
Another essential question to exploit diversity gain is the selection of a single
optimalhelperormultipleuncorrelatedhelperswithlimitedinterferenceandpower
consumption. From the physical-layer standpoint, multiple helpers can improve
diversity to achieve a higher signal-to-noise ratio (SNR) and better performance.
However, from the link layer’s point of view, multiple relays may not perform
better than a single best relay, because of the overhead to coordinate multiple
relays and manage transmissions. Intuitively, the more helpers, the more complex
the coordination. Besides, multiple helpers may increase energy consumption and
possibilities of collisions (e.g., due to the hidden terminal and exposed terminal
problems).
