Relay Mapping Scheme Design And Performance Analysis Of Physical Layer Network Coding With High Order Modulation

Network coding is considered as a revolutionary technology, and its important breakthrough in the field of information theory has stimulated its application in wireless communication. The most representative Research scenario is the cooperative wireless two-way relay network based on physical layer network coding. Compared with the traditional one-way relaying transmission method, physical layer network coding for two-way wireless relaying scheme based on, allowing relay nodes to process the information interaction, which can effectively reduce the two-way flow of information in a wireless relay network transmission time overhead, increase the throughput of the network. At present, the physical layer network coding has received the attention of the international academia and industry.In this paper, the research results of physical layer network coding in wireless communication field are summarized firstly. Starting from two common ways of relay, the basic ideas and implementation schemes of network coding and their respective advantages and disadvantages are introduced. Compared with the traditional network coding, the physical layer network coding is significantly improved in the information exchange rate. BPSK two low order modulation based, discusses the symmetrical modulation of physical layer network coding specific programs and theoretical bit error rate(BER); cited an asymmetric modulation superposed signal constellation decision method.For the physical layer network coding relay mapping scheme based on high order modulation, the 8PSK-QPSK and 16QAM-QPSK superposition signal expression is derived by the channel equalization pretreatment. Draw superimposed signal constellation, divide the superimposed signal decision region, calculate the superimposed signal decision threshold. For the ARB two-way relay system model, all the possible relationships between the two user information are statistically encoded and mapped. The average error probability of the relay is calculated by the network coding of the physical layer, and the power ratio of the transmitted signal to the two side users is closely related. The simulation results show that the ratio of the transmitted power to the transmitted power of the two side users can reach a minimum of the minimum value when the physical layer network coding relay error probability is minimum.The performance analysis of the 16 QAM modulation physical layer network coding is carried out by mod4 mapping scheme. The theoretical error rate of the relay map before and after mapping is deduced. The simulation results show that the physical layer network coding can improve the system throughput, while the error performance only drops a little. In addition, a simple improvement method is proposed because it can not realize the one to one correspondence of the superposition signal and network coding. Finally, combined with the low density parity check(LDPC) code, the physical layer network coding and channel coding are combined.