The Research On Multicast Beamforming And D2D Technologies In LTE Trunking System

Wireless multicast is a type of service between unicast and broadcast, which canimprove frequencyefficiencyand expandsystem capacity by sending the same messageto groups of users on the same time-frequency resource block.Recently, inpracticalcommunication systems, multicast services are not only surveyed widelybut alsoformed as MBMS (Multimedia Broadcast and Multicast Service)protocolsandstandards in LTE (Long Term Evolution) and WiMAX (World interoperability forMicrowave Access).In contrast, thedevelopment of private networksystem, especially trunkingcommuncation system,is lagging behind, whose main business ismulticast.Besides,there are no unifiedindustry standards.Therefore, in order to shorten thegapbetweenthe public networksystems and achievemultimedia transmissionwithhigh-quality,high-speed,low-resource-occupancy-rate, learningandstudyingthe keytechnologiesin publicnetworkis imperative.In space domain, beamforming in the downlink with multi-antenna technologycan improve the quality of multicastservice and spread the coverageoftheBS (BaseStation) by spatial diversity. In time domain, based on the characteristic that multicastcapacity is limitedtotheworst CSI (Channle State Information) among usersinthe samegroup, ARQ (Automatic Repeat Request) technologycan be taken into account tothemulticasttransmission rate andthefairness among users.Therefore, fromthe prospect of spatialdiversity andtimediversity,multicastbeamformingand D2Dtechnologies are fully studied throughthis paper:Chapter2summarizes the basic principal ofmulticastbeamforming. Firstly, thebemforming models are built according tosinglegroupandmuti-group scenarios;Secondly,when the CSIis completelyknown to the BS, the QoS(Quality ofService),andtheMMF(Max-MinFair) guidelinesare introducedintomulticastbeamformingalgorithms, andtheconceptofSDR (semidefiniterelaxation),randomization, andpower controlin the post-process are also talked; Finally,the quality of beamforming and isdiscussed through simulation.Chapter3discusses the multicastbeamformingalgorithmswhich is suitabletotrunking system. Firstly, in the scenario of trunking system, multicast beamformingbasedonuser’sAoAis proposed;secondly, simulation analysis ontheangular interval ofusers, the number of users,thenumberofantennas at BS, theSNR(SignaltoNoiseRatio)or SINR (SignaltoInfererence plusNoise Ratio)thataffectthe beamformingperformance;finally,an adaptive multicast beamforming scheme is proposed.Chapter4studies the D2D technology in trunking system. Firstly,the combinedmodel of multicast andD2D technologies in Two-Phase is established; secondly,according totwo existing relay-selection schemes called SH (Success to Help) andAH(Asking for Help), an improved scheme called OH (Offer Help) is proposed byintroducing the Battery-Information of UE (User Equipment); thirdly, a scheme calledABIB (Average Battery Information-Based) is introdued from the prospect ofprotecting low-battery UEs; finally, performances of all relay-selection schemes areevaluated through simlulaitons.Chapter5concludes this dissertation and discusses the future research work.