Mismatched Bit-Interleaved Coded Noncoherent Orthogonal Modulation

We consider several low-complexity decoding metrics for bit-interleaved coded modulation (BICM) with orthogonal signaling and noncoherent detection. Using the generalized mutual information (GMI) as the relevant performance measure, we demonstrate that only a small performance degradation is entailed by using these mismatched metrics instead of the maximum likelihood (matched) metric. Furthermore, for coded transmission with sum-product symbol-by-symbol (SBS) decoding, we illustrate that metric scaling with a constant factor can improve the throughput performance of these metrics.