Performance analysis of Alamouti-coded OFDM systems over spatio-temporally correlated underwater acoustic channels

In this paper, we analyze the performance of Alamouti-coded orthogonal frequency division multiplexing (OFDM) systems over time-varying underwater acoustic (UWA) channels. A realistic UWA channel model has been considered, which can be correlated in either time or space or simultaneously in both domains. An exact analytical expression for the bit error probability (BEP) is necessary to analyze accurately the performance of Alamouti-coded OFDM systems over the spatio-temporally correlated UWA channel model. Hence, by using this UWA channel model, an expression has been derived for the BEP of Alamouti-coded OFDM systems assuming that the receiver knows perfectly the channel state information. The BEPs of two special cases are also studied, where the UWA channel is only correlated in either time or space. The performance of the Alamouti-coded OFDM system over UWA channels has been assessed for different maximum Doppler frequencies and antenna spacings. All theoretical results are validated by system simulations.