Bit-interleaving diversity for HARQ transmission over MIMO frequency-selective channels

In this paper, we investigate the performance of a bit-interleaving diversity (BID) scheme for multiple packet transmissions over multiple-input multiple-output (MIMO) frequency-selective channel in the context of hybrid automatic repeat request protocols. We show under the maximum likelihood decoding rule that a BID scheme outperforms an identically interleaved transmit scheme. Moreover, we identify and characterize three types of diversity resulting from the BID scheme: modulation diversity, multiplexing diversity, and interference decorrelation resulting in an enhanced detection performance. By using a distance spectrum analysis, we evaluate their respective importance according to the used modulation and the transmission scenario. Some interleaving design rules are given in order to enhance further the overall transmission diversity. The receiver is implemented using a turbo-equalizer structure with packet combining based on separate linear equalization followed by joint decoding. Simulation results show the efficiency of the BID scheme for different transmission scenarios.