The CEEFQPSK Scheme for Two-Way Relay Communication Systems with Physical-Layer Network Coding

A physical-layer network coding (PNC) scheme based on CEEFQPSK (constant envelope enhanced FQPSK) is established for satellite communications. The scheme is implemented for uplink and downlink. In the uplink, the two signals to be sent are modulated into electromagnetic wave signal by CEEFQPSK in two channels (I, Q) and broadcasted to the relay node. At the same time, the electromagnetic wave signal is superimposed on the relay node and mapped into a binary bit, and then it will be modulated and broadcasted to the two terminals. In the downlink, soft information is received according to the maximum posterior probability criterion, and the required information is de-mapped with its own information. The bit-error rate (BER) and throughput of the entire system are analyzed by simulation. Theoretical analysis and simulation results show that the BER of the physical-layer network coding scheme using this method is close to that of the traditional scheme and network coding scheme, but the throughput is higher than the other two.