Research Of Wireless Cooperative Two-Way Relay System Anti-Interference Technology Based On Physical-Layer Network Coding

In a two-way wireless cooperative relay system, most of the research is a cellularcommunication system based on a single area of the simlplest three node transmission mode,application of three slots of network coding scheme for complete bidirectional data flowtransmission. However, combined with the actual situation of communication systems, for thetwo-way relay channel transmission scenes in the single cell, this paper study the twotransmission model: Groups of users through relay exchange information and multiple usersthrough relay exchange information. Discuss and analysis respectively, application of twoslots of physical-layer network coding(PNC) scheme, then give the model and for thegenerated interference using MIMO combined with network coding to anti.First, introduce bidirectional cooperative relay channel based on the PNC, given thetransmission model that single group of users through a single relay to exchange information,the relay adopts AF protocol, and according to the different channel conditions, analyze theoutage probability changes of the two users, simulation results show that the outageprobability curves are the same when the channel completely symmetric, and have superiorperformance, laid the foundation for the following study.Second, extended to groups of users transfer scene, using the spatial multiplexingtechnique in MIMO combined with PNC to gather multiple users’ and pairs of users’information together, needed to design beamforming metrics in the relay, one is a proposedbeam-forming scheme, the other is null space vector selection scheme, theoretical analysisand formula deduction respectively, the simulation results show that the proposed schemehas better performance than the existing scheme, and both of the two methods can obtaingreater diversity and multiplexing gain, the most important is that interference can beeliminated effectively.At last, introduce precoding technique in MIMO, given the multiple uses MIMObroadcast channel(downlink channel)mode, analyze precoding algorithms based on blockdiagonalization, in the ideal case which can completely eliminate the interference caused bymultiple users. For the second transfer scene, given the transmission model that multiple usersthrough a single relay to exchange information with base station, introduce the existing scheme that time sharing combined with network coding, for the shortcoming anddeficiencies, propose a new scheme that precoding combined with PNC, only using two slotsto finish communication, by designing precoding metrics in base station and relay to antiinterference caused by multiple users. Then compared with the two schemes, the simulationresults show that the proposed scheme can get the better performance at high SNR, alsoobtain the higher diversity gain and multiplexing gain.