Bandwidth-Efficient Multi-User Cooperation with Optimal Transmission

Cooperative transmission is an efficient way to combat fading for wireless communication. In this paper, a bandwidth-efficient multi-user cooperation scheme is proposed, that is based on TPC(Turbo Product Codes)-BICM(Bit-Interleaved Coded Modulation). In the multi-user cooperation, we use distributed transmission to achieve diversity gain. The bit error rate(BER) performance is discussed and BER upper bound is deduced. Modulation order M, component codes and cooperation level α_i are the main parameters that influence system performance. Assumed that the first two parameters are fixed, we discussed the optimal α_i value on principle of minimum BER. An optimal transmission rule is presented. When all the uplink channels are same, uniformity distribution is optimal. Simulation results in slow fading show that the BER performance curve approach the upper bound at high SNR. In a general way, the optimal transmission outperforms uniformly transmission.