Springer Series in Wireless Technology SeriesEditor RamjeePrasad,CtrforTeleInFrastruktur,C1-107,AalborgUniversityCtrfor TeleInFrastruktur,C1-107,Aalborg,Denmark Springer Series in Wireless Technology is a series of monographs, contributed titlesandadvancedtextbooksexploringthecuttingedgeofmobiletelecommunica- tion technologies and promulgating them for the benefit of academic researchers, practicing engineers and students. The series encourages contributions in the theoretical, experimental and practical engineering aspects of wireless communi- cations—voice,dataandimagetransmission.Topicsofinteresttotheseriesinclude butarenotlimitedto: • codingandmodulation; • cognitiveradio; • full-duplexwirelesscommunication; • model-freedesign; • multipleaccess; • resourceallocation; • usesofdigitalsignalprocessinginwirelesssystems; • wirelessenergytransfer; • wirelessnetworks:4G,5Gandbeyondandnext-generationWiFi;adhocwireless networks, device-to-device networks; heterogeneous mobile networks; wireless sensornetworks; • wirelessopticalcommunications. Proposalsforthisseries(pleaseusetheproposalformthatcanbedownloadedfrom thispage),canbesubmittedbye-mailtoeitherthe: SeriesEditor Professor RamjeePrasad Department of Business Development and Technology, Aarhus University, Birk Centerpark 15,8001, Innovatorium, CGC, 7400 Herning, Denmarke-mail:[email protected] orthe In-houseEditor Mr. Oliver Jackson Springer London, 4 Crinan Street, London, N1 9XW, United Kingdome-mail:[email protected] · · Shih-Chun Lin Tsung-Hui Chang · Eduard Jorswieck Pin-Hsun Lin Information Theory, Mathematical Optimization, and Their Crossroads in 6G System Design Shih-ChunLin Tsung-HuiChang DepartmentofElectricalEngineering SchoolofScienceandEngineering NationalTaiwanUniversity TheChineseUniversityofHongKong Taipei,Taiwan Shenzhen,China EduardJorswieck Pin-HsunLin InstituteforCommunicationsTechnology InstituteforCommunicationsTechnology TechnischeUniversitätBraunschweig TechnischeUniversitätBraunschweig Brunswick,Germany Brunswick,Germany ISSN 2365-4139 ISSN 2365-4147 (electronic) SpringerSeriesinWirelessTechnology ISBN 978-981-19-2015-8 ISBN 978-981-19-2016-5 (eBook) https://doi.org/10.1007/978-981-19-2016-5 ©TheEditor(s)(ifapplicable)andTheAuthor(s),underexclusivelicensetoSpringerNature SingaporePteLtd.2023 Thisworkissubjecttocopyright.AllrightsaresolelyandexclusivelylicensedbythePublisher,whether thewholeorpartofthematerialisconcerned,specificallytherightsoftranslation,reprinting,reuse ofillustrations,recitation,broadcasting,reproductiononmicrofilmsorinanyotherphysicalway,and transmissionorinformationstorageandretrieval,electronicadaptation,computersoftware,orbysimilar ordissimilarmethodologynowknownorhereafterdeveloped. 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The registered company address is: 152 Beach Road, #21-01/04 Gateway East, Singapore 189721, Singapore Preface Withthecommercializationof5Gcommunications,industrialandacademiccommu- nitieshavebeguntoconceivethetechnologyandrequirementsofthenextgeneration of communications. This monograph provides a solid understanding of the funda- mentaltoolsandmethodsfrominformationtheoryandmathematicalprogramming withspecificapplicationsto6Gsystemdesigns.Thefuture6Gsystemswillincorpo- ratethe5GcommunicationnetworkwithArtificialintelligenceinInternetofThings (AIoT)andopentheeraof“InternetofIntelligence”,whichwilllinkpeople,things, and information with smart computing. The smart Internet collects environmental information from networked sensors, and people or things can obtain processed and useful information through the smart Internet. It is expected that the informa- tiontheory,mathematicaloptimization,andtheirintersectionwillplayanimportant role in the design. Information theory offers fundamental guidelines on optimal datatransmissionandstatisticalinferenceoverthenetwork,whiletheoptimization theoryallowssystematicmodellingandalgorithmicmethodstoapproachthemand performfurtherdataprocessing.Thismonographwillprovideanover-archofthese twofieldsandtheirinterplay,andalsodemonstratehowtheyareappliedtothe6G systemdesigns. Inthefirstpartofthisbook,informationandoptimizationtheoryarediscussed. Two types of system design approaches will be discussed, that is, centralized and distributed ones. The former suits 6G systems pursuing maximum performance, whereperfectnetworkinformationisavailableatnodes,whilethelattersuitsAIoT applicationswhencoordinationbetweennetworknodesislimitedduetoconstraints onavailableresources.InChap.1,itstartsfromtheinformationtheoryforcentralized wireless networks where all nodes have global channel state information (CSI). Next,inanetworkwherenotallnodesfullycooperateorprovidetheirlocalCSI,the informationtheoryofthisdistributednetworkwillbepresentedinChap.2.InChap.3, wediscussthestatisticaldetectiontheories,wherethedistributedpartsofthemalso servesasabasisofdistributedlearning.Tofurtheroptimizetheschemesdiscussed, centralizedanddistributedoptimizationtheorieswillthenbeaddressedinChaps.4 and 5, respectively. Not only the convex optimization but also the state-of-the-art non-convexmethodswillbeincluded. v vi Preface Inthesecondpart,applicationsoftheoriesinthefirstpartandtheirintersection will be addressed. Note that 3GPP already provided the 5G New Radio, with the servicesandapplicationsbeingclassifiedasfollows: • Enhanced mobile broadband (eMBB): This use case mainly focuses on high data-ratehuman-centriccommunications.Augmentedrealityandhigh-resolution videocommunicationarebothapplicationexamples. • Massivemachinetypecommunications(mMTC):Thisusecasehasaverylarge numberofconnecteddevices,andisalsoknownasIoT.Lowcostandlongbattery lifeareimportantforthesedevices. • Ultra-reliableandlowlatencycommunications(URLLC):Thisusecasepromises toservemultipleautonomousmachineswithhighreliabilityandlowlatency.Its examplesincludesmartgrid,InternetofVehicles,andwirelesscontrolofindustrial manufacturing. Wearguethattheaforementionedusecasesarealsoimportantfor6G.InChap.6, wefocusontheresourceallocationofhighdata-rate6Gnetwork.Toachievehigh trafficcapacity,basestation(BS)scanfullycooperateunderthelowrequirementof mobilityandbecomeacentralizedsupertransmitterknowingperfectCSI.However, when users desire high mobility, the channel state information at the transmitter (CSIT)isnotperfectandBSsmayevennotfullycooperate.Thecentralizedinfor- mationandoptimizationtheorieswillbeimportantforthefirstpartofChap.6,while the distributed theories are essential for the second part. Next, URLLC should be extended toallowmultipleusersin6G,andthusnotonlyfiniteblocklength infor- mationtheorybutalsonon-convexoptimizationareneeded,asdiscussedinChap.7. TowardsInternetofIntelligence,inChap.8wediscussFederatedLearning(FL)asa formofAIoT.Inthisscenario,aserverperformsdistributedparameteroptimization throughquantizedinformationfromcapacity-limitedlinksofedgedevices.Finally, securityissuesautomaticallyariseindistributedinformationsystems.Twoexamples, thedistributedByzantinedetectionanddistributedsecrecy,arediscussedinChap.9. Notations:Inthisbook,ifnotspecificallymentionedineachchapter,(differen- tial)entropyandmutualinformationaredenotedbyH(·)andI(;),respectively,and randomvariablesaredenotedinitaliccapitals.Deterministicmatricesaredenoted in bold-face capitals. For matrix G, Tr(G) and Rk(G) denote the trace and rank; GT and G† denote the transpose and conjugate transpose, respectively. G−1 and s |Gs|aretheinverseanddeterminant(cid:2)ofasquarematrixGs.TheFrobeniusnormof a matrix G is denoted by (cid:2)G(cid:2) := Tr(GG†) and I denotes the identity matrix F n ofdimensionn.Thepartialorderingbetweensymmetricmatricesisdenotedby(cid:3) and(cid:4),forexample,G (cid:4) G (“largerthanorequalto”betweenmatrices)means 1 2 (G − G ) is a positive semi-definite matrix. The Kronecker product between 1 2 matricesis⊗.Pleasereferto[1]fordetailsofthesematrixoperations. Preface vii Randomvectorswillbedenotedbylowercaseboldfontorwithasuperscriptindi- catingtheirlength(e.g.,aor A[1:T] =(A ,...,A )).Forarandomvectora,(cid:2) or 1 T a Cov(a)denotesitscovariancematrix.ForcomplexGaussianvectora∼CN(0,(cid:2) ), a weassume itiscircularly symmetric such thatitsdistributionis completely deter- minedbythecovariancematrix(cid:2) .ThesameassumptionisappliedtoarealGaussian a vectora∼N(0,(cid:2) ). a The indicator function 1{.} is 1 if its input event is true and 0 otherwise. Also (x)+ = max{x,0}.Theset{1,...,N}isdenotedas[1 : N]or[N],where N isa positiveinteger. Taipei,Taiwan Shih-ChunLin Shenzhen,China Tsung-HuiChang Brunswick,Germany EduardJorswieck Brunswick,Germany Pin-HsunLin Reference 1.HornRA,JohnsonCR(1985)Matrixanalysis.CambridgeUniversityPress,Cambridge,UK Acknowledgements PartoftheworksofShih-ChunLinisfundedbyMinistryofScienceandTechnology, Taiwan,andbyNationalTaiwanUniversityunderGrantNTU-CC-111L894402.S.- C.LinthankshisstudentsandDr.Yen-FuChouforpreparingthisbook,andmany colleaguesforhelpfuldiscussions.Especially,Prof.I-HsiangWang,Prof.Yu-Chih Huang,Prof.Yu-JuiHuang,andProf.AlirezaVahid.TheworkofTsung-HuiChang issupportedinpartbytheShenzhenScienceandTechnologyProgramunderGrant JCYJ20190813171003723 and RCJC20210609104448114, in part by the NSFC, China,underGrant62071409,andinpartbytheGuangdongProvincialKeyLabo- ratoryofBigDataComputing.Tsung-HuiChangwouldliketoacknowledgeMiss Songyang Ge and Miss Yanmeng Wang for fruitful discussions and for preparing the materials for Chaps. 5 and 8, respectively. The discussion with Dr. Chao Shen at Shenzhen Research Institute of Big Data for Sect. 6.2.6 is also acknowledged. Part of the work of E. Jorswieck is funded by the Federal Ministry of Education and Research (BMBF, Germany) through the 6G Research and Innovation Cluster 6G-RICunderGrant16KISK020KandbytheGermanResearchFoundation(DFG) under grant JO 801/23-1. E. Jorswieck would like to acknowledge the discussions withthecolleaguesfromthejointGerman-IranianDFG-INSFfundedprojectunder grant JO 801/24-1, and the groups of Dr. Mokari and Dr. Javan. Furthermore, E. JorswieckacknowledgesdiscussionswithDr.Matthiesenaboutthematerialonnon- convexoptimizationinSect.4.2,inparticularonbranch-and-boundandmixedmono- tonicprogramming,withDr.Zapponeonfractionalprogramming,withDr.Björnson onmonotonicprogramming.FortheresultsinSect.6.1,E.Jorswieckacknowledges fruitfuldiscussionswithMr.Rezvani,forSect.6.2.1withMr.ZakeriandMr.Khalili, forSect.6.2.3withDr.Matthiesen,Dr.HellingsandDr.Utschick.Finally,thediscus- sionswithDr.ShehabandDr.AlvesoneffectiveenergyefficientURLLC(Sect.7.1) isacknowledged. ix Contents 1 InformationTheoryinCentralizedWirelessNetwork .............. 1 1.1 SingleUserMIMOChannel ................................. 2 1.1.1 Capacity-Achieving Code foraGaussian(SISO) Channel ............................................ 4 1.1.2 BeamforminginSIMOandMISOChannels ............. 20 1.1.3 MIMOCapacitywithFullCSI ......................... 23 1.1.4 MIMOOFDMforMulti-pathChannels ................. 30 1.2 Multiple Access Channel with Global Channel State Information ................................................ 34 1.2.1 GaussianMultipleAccessChannel ..................... 34 1.2.2 SuccessiveInterferenceCancellationattheMAC Receiver ............................................ 37 1.2.3 MIMOMultipleAccessChannel ....................... 39 1.3 BroadcastChannelwithGlobalChannelStateInformation ....... 41 1.3.1 GaussianBroadcastChannel ........................... 41 1.3.2 SuccessiveInterferenceCancellationattheStronger Receiver ............................................ 44 1.3.3 MIMOGaussianBroadcastChannel .................... 46 1.3.4 DirtyPaperCodingwithFullCSIT ..................... 48 1.4 Conclusion ................................................ 60 References ..................................................... 60 2 InformationTheoryinDistributedWirelessNetwork .............. 63 2.1 CSIFeedbackinSingleUserChannel ......................... 64 2.1.1 ChannelStatistics .................................... 64 2.1.2 CodinginaFastFadingChannel ....................... 66 2.1.3 CodinginaSlowFadingChannel ...................... 72 2.2 IntermittentBroadcastChannelswithDistributedCSI ........... 78 2.2.1 BinaryExpansionModelsofIntermittentGaussian BroadcastChannels .................................. 79 xi xii Contents 2.2.2 Hybrid Intermittence State Information attheTransmitterandReceivers ........................ 81 2.2.3 DoF Regions for Channels with Perfect CSIT forReceiver1 ....................................... 82 2.2.4 DoFRegionsforChannelsWithoutPerfectCSIT forReceiver1 ....................................... 88 2.3 IntermittentInterferenceChannelswithDistributedCSI .......... 96 2.3.1 GaussianInterferenceChannels ........................ 96 2.3.2 DoFRegionsofIntermittentGaussianInterference Channels ........................................... 98 2.3.3 Intermittent Gaussian Interference Channels withLocalDelayedCSIT ............................. 110 2.4 ComputationOverIntermittentMultipleAccessChannel ......... 112 2.4.1 DoF for Computation Over a Gaussian Multiple AccessChannel ...................................... 113 2.4.2 DoFBoundsforComputationOvertheTwo-UserCase .... 119 2.4.3 AchievableDoFfortheComputationOverK-User Case ............................................... 124 2.5 Conclusion ................................................ 128 References ..................................................... 128 3 CentralizedandDistributedDetection ............................ 131 3.1 CentralizedDetectionTheory ................................ 132 3.1.1 CentralizedHypothesisTesting ........................ 132 3.1.2 CentralizedQuickestChangeDetection ................. 135 3.2 DistributedDetectionTheory ................................. 138 3.2.1 DistributedHypothesisTesting ......................... 138 3.2.2 DistributedQuickestChangeDetection .................. 141 3.3 Conclusion ................................................ 142 References ..................................................... 142 4 CentralizedMathematicalOptimization .......................... 145 4.1 ConvexOptimization ....................................... 145 4.1.1 ConvexSetsandFunctions ............................ 146 4.1.2 ConvexOptimizationProblems ........................ 149 4.1.3 LagrangeDualityTheorem ............................ 151 4.1.4 TheKKTConditions ................................. 153 4.1.5 ConcludingRemark .................................. 155 4.2 Non-convexOptimization ................................... 155 4.2.1 SequentialConvexApproximation ...................... 156 4.2.2 Semi-definiteRelaxation .............................. 157 4.2.3 FractionalProgramming .............................. 159 4.2.4 MonotonicProgramming .............................. 162 4.2.5 Branch-and-Bound ................................... 166 4.2.6 MixedMonotonicProgramming ....................... 169