Analysis of Mutual Information Based Soft Forwarding Relays in AWGN Channels

In this paper, we analyze the error performance of the mutual information based forwarding (MIF) scheme for a memoryless parallel relay network in additive white Gaussian noise (AWGN) channels. The analytical expression for soft noise variance is first derived. Note that in the literature, the exact soft noise variance could only be evaluated by Monte Carlo simulation due to the lack of its analytical form. The derived soft noise variance expression only relies on the transmit signal-to-noise ratio (SNR), without the need to have the knowledge of actual or estimated information bits. With the expression of the soft noise variance, we derive an approximate bit error rate (BER) expression for a parallel relay network employing MIF scheme. The derived soft noise variance and system BER expressions are shown to be in tight match with Monte Carlo simulation results.