System design for bit-interleaved coded square QAM with iterative decoding in a Rician fading channel

Abstract. One-step iterative decoding for bit-interleaved coded QAM with conventional Gray mapping can give a significant improvement of performance for fading channels. Furthermore, iterative decoding with ideally known feed back bits is easier to analyze theoretically than non-iterative decoding. In this paper, we derive analytical expressions for the pairwise error probabilities for bit-interleaved coded QAM with correct feed-back bits. They are used to obtain union bounds for the bit error rate. Numerical simulations show that the performance with only one feedback step comes very close to these ideal theoretical curves. They are therefore a reasonable guideline for system design to choose the right code rate and modulation level for bit interleaved coded QAM in a fading channel.