Power Optimization And Synchronization Technology Of D2D Communication Underlaying LTE Cellular Networks

Device-to-device(D2D) communication technology allow the terminals to connectand communicate directly.compared with cellar communication,D2D communicationdoes not need to relay data via a base station,it is possible to reduce the base stationload.Therefore,D2D communications underlaying cellular networks become aimportant research area recently.D2D communications underlaying cellular networkscan reduce the base station load effectively in some specific communicationscenarios,but the combination of them has many problems to be solved.The spectrum demand has been estimated to be1280-1720MHz in2020for a lowand high user demand scenario respectively.However,in the last World RadioCommunication Conference(WRC’07) less than600MHz have been allocated tomobile communication systems.Exclusive allocations of more bandwidth to mobilecommunication system in the near future is unlikely since the spectrum below5GHzhas already been full allocated. If D2D communication share resource with cellularnetwork,the interference between two services exist.If D2D communication do notshare resource with cellular network,D2D links need to be allocated exclusiveresource.However it’s very difficult to do this because spectrum resources of wirelessmobile communication is very tight.If D2D communication is assigned unlicensedspectrum,the QoS of D2D communication can’t be guaranteed,so the best choice isD2D communication multiplexing with cellular communication spectrum resourcesand controlling the transmitted power of D2D communication at the same time.Thearticle raised a system model to analyze the methods of power control of D2Dcommunication and tried to find the best power optimization method.The article discussed and analyzed the advantages of combining D2D system withLTE system and the scenarios D2D communication technology can beused.Besides,the resource sharing problem is discussed.The result imply that D2Dcommunication can not only share spectrum resources with cellular communicationorthogonally but also multiplexing with cellular communication spectrum resources.The article also discussed the synchronization problem of D2D communication underlaying cellular networks.Although the cellular terminals can maintainsynchronized with the base station,they are not synchronized with each other.Whentwo terminals start D2D communication,the synchronization signal need to bedesigned.In this part,the synchronization mechanism of LTE system is discussed andthen the synchronization mechanism of D2D communication underlay cellularnetworks is also discussed.After that,two methods of synchronization israised.Finally,the performance of the two methods is compared.