Joint modulation and network coding in uplink relaying channels: A complex-valued 3-ary approach for BPSK modulation

Wireless network coding technology has received a lot of attention since it can improve the bandwidth efficiency to a large extent for relay networks. In order to avoid the requirement of direct transmission and enhance the transmission quality of uplink decode-and-forward relaying channels, a network coded mapping scheme is proposed in this paper. The relay first detects the received signals into bit-level, then jointly modulates the two data bits together in the complex-valued constellation. In the case of binary phase shift keying modulation, a 3-ary mapping approach is presented in order to further decline the error probability. To evaluate the proposal´s performance, the tight closed-form expression of bit error probability for additive white Gaussian noise and Rayleigh fading channels are derived, respectively. Simulation results show the performance gain of the proposed scheme is significant in comparison with conventional mapping schemes.