Space-time-frequency coded-OFDM employing adaptive multiple antenna selection over WLAN fading channels

In this paper we present an adaptive multiple antenna selection (AdMAS) employing a maximum of 4 transmit (4 Tx) and 1 receive (1 Rx) antenna in conjunction with coded space-time-frequency (STF) orthogonal frequency division multiplexing (OFDM) over wireless local area network (WLAN) IEEE 802.11 channels. Our coded STF-OFDM is a product of 4-QAM STF block code which has been concatenated with convolutional codes of rate 1/2 with length of 5. In transmitting data we adaptively select channel with least fade and turn off the most faded channel at the transmitter side. We determine levels of fading of each transmitter channel based on the statistical average of the channel impulse response (CIR). We also compare results when level of fading is based on the variance of the CIR. Results show that, the employment of AdMAS does not significantly contribute to performance improvement (less than a dB gain), either adapting to mean or variance-based scheme, at shorter delay spreads (e.g. 100 ns). However at longer delay spreads (e.g. 1.3 μm) our proposed AdMAS scheme outperforms coded STF-OFDM scheme by as much as 4 dB to achieve a BER of 10^-3.