Investigation On Terminal Cooperative Multicast Technology In LTE-S System

With the increasing popularity in smart phones, broadband multimedia services havealready become a hotspot in current global mobile business. It is a great challenge tochoose a suitable multicast transmission rate to satisfy all users and improve thesystem throughput simultaneously for Point to Multipoint multicast technology.Terminal cooperative multicast transmission, which conducts users with good channelcondition in multicast group forward the service data to the users with bad channel,effectively improve both fairness and throughput by providing path loss gains anddiversity gains.However, there are also a series of challenges in multicast transmission based onterminal cooperation. Firstly, current researches about multicast transmission based onterminal cooperation all focus on single-cell multi-user scenarios without consideringmulti-cell multi-user scenarios, let alone research the cooperative multicasttechnology in LTE-A system. Whether it is necessary to introduce terminalcooperation technology into the LTE-A E-MBMS is a important problem to be solved.Secondly, though cooperative multicast is able to improve the system total throughput,the system total energy consumption could increase significantly when the numbers ofrelays increase as the relays consume additional energy to transfer the received data.Therefore, it is a big challenge for cooperative multicast to improve systemthroughput while keeping high energy efficiency. Finally, in LTE-A system, it remainsunknown if the cooperative multicast is always superior to MBSFN. Aiming to solvethese problems, this thesis investigates the cooperative multicast scheme in LTE-Asystem. The main contributions of this thesis are listed as follows:(1) Based on3GPP physical layer and system level protocols, this thesis design andbuild a LTE-A unicast simulation platform, including multi-cell topo model、multi-user drop model、path loss and shadowing model、SCM small-scale fadingmodel、SINR calculation model、link abstraction model、modulation and codingscheme selection model and throughput calculation model. Then the simulationresults calibrate with3GPP protocols TR36.814to verify the accuracy and validityof system simulation platform.(2) According to3GPP E-MBMS related protocols, this thesis design and build aLTE-A MBSFN simulation platform based on LTE-A unicast simulation platform.The simulation results show the UE SINRs are too high in MBSFN center cellwhich results in wasting BS power, while in MBSFN edge cell the UE SINRs arepoor to satisfy the low level modulation and coding scheme. So this thesisproposes that it is necessary to introduce the terminal cooperative multicasttechnology into the E-MBMS in LTE-A system in order to guarantee the systemcoverage and reduce the BS power with providing data rate.(3) This thesis proposes a multicast scheme combining the MBSFN and terminalcooperative technology in LTE-A system using strongest power relay selectionstrategy and CP combing is employed to receive signals from relays. Withprovided data rate and system coverage, simulations are conducted to compare the energy between MBSFN and terminal cooperative multicast. It is shown in ourstudy that when the number of users is small, the MBSFN can provide betterperformance than the terminal cooperative multicast. However, when the usernumber is large, the system throughput of terminal cooperative multicastsignificantly outperforms that of MBSFN.