Performance analysis of a system using coordinate interleaving and constellation rotation in frequency-selective fading channels

Performance analysis of a system employing coordinate interleaving and constellation rotation in frequency-selective fading channels is presented. The achievable performance for L-branch microdiversity using maximum ratio combining (MRC) receiver is analyzed and an upper bound on the average probability of bit error (P_b) is presented. Exact closed form expressions for pairwise error probability (PEP) are derived for single-symbol transmission in a multi-path fading environment. It is shown that the derived upper bound is tight for high signal-to-noise ratios (SNR). The optimum rotation angles are found by minimizing the upper bound and it is shown that the optimum rotation angles change as the number of diversity branches is increased. Furthermore the effect of different signal constellation mappings on the system performance is also presented and it is shown that the Gray signal constellation mapping is not necessarily the best option for the entire range of signal constellation rotation.