Analysis of per-tone transmit antenna selection in OFDM systems with Alamouti coding

We study the performance of per-tone transmit antenna selection in OFDM systems with Alamouti coding. In particular, we analyse the diversity and coding gains of such systems, and compare these gains with the respective performance metrics for single-antenna selection performed on a pertone basis. Our analysis demonstrates that although the gain of single-antenna selection is superior to that of Alamouti encoded transmissions, this advantage diminishes quickly with increasing numbers of transmit and/or receive antennas. Specifically, we show that the diversity orders of the two schemes are identical, and there is less than 1 dB difference in the coding gains when more than two transmit antennas are employed. Consequently, one can still achieve performance close to that of single-antenna selection in systems that only support Alamouti coding by employing transmit antenna subset selection on a per-tone basis.