Diversity Gain and Coding Performance of OST-CPM System in Spatially Correlated Channels

The Chernoff bound on Pair-Wise Error Probability (PWEP) performance of orthogonal space-time coded CPM (OST-CPM) systems is investigated, for two transmit antennas, over spatially correlated channels. Approximate Chernoff bound for high Signal-to-Noise Ratio (SNR) is derived to evaluate the diversity gain and coding performance in correlated channels. The achievable diversity gain of this system decreases due to the signal correlation between the antennas. Simulation results show that the error performance over a correlated channel is degraded when the correlation coefficient increases. And the penalty on the code performance increases a lot in fully correlated channels. It can also be seen that the diversity gain decreases when the channel is fully correlated, which matches well with the theoretical analysis. The upper bounds can be looser when diversity order decreases.