Optimized Polar Coded Selective Relay Cooperation With Iterative Threshold Decision of Pseudo Posterior Probability

This paper proposes an optimized polar coded selective relay cooperation with an iterative threshold decision of pseudo posterior probability to solve the excessive redundancy of received signals and the high decoding complexity in a selective decode-and-forward (SDF) relay scheme. By sharing antennas of a relay node, a polar coded cooperation scheme is illustrated in a three-node relay transmission model, accompanied by an SDF protocol. Simultaneously, the SDF protocol is completed according to the channel status information at the relay node. In the logarithmic belief propagation algorithm, an expression of pseudo posterior probability-based stopping iteration threshold with independent and variable signal-to-noise ratios is derived to decide convergence condition and thus timely stop the iterations for low decoding complexity. And an extrinsic information transfer chart is also used to verify the completion of the iterative process. In addition, an information detection factor is introduced to check decoded bits correctly by the change of it, thereby reducing the average number of decoding iterations. It also accelerates the convergence speed of the BP algorithm by setting threshold and prejudgment, thereby improving the decoding efficiency. Simulation results show that the proposed polar coded relay cooperation scheme obtains over 2 dB performance gain, when the bit error rate (BER) is lower than 10
^-3
, compared with the existing low-density parity-check codes related schemes. It also reduces the complexity of the BP algorithm by stopping the iteration of high-reliability nodes at the cost of performance loss within 0.5 dB. Therefore, the proposed scheme obtains both good BER performance and low complexity, which endows its good applications in cooperative wireless communications.