A simple transmit antenna diversity technique for OFDM and its detection using Viterbi algorithm

We investigate a transmit antenna diversity (TAD) technique for orthogonal frequency division multiplexing (OFDM). Multiple cyclic-shifted signal vectors are transmitted through multiple antennas to introduce transmit diversity. From this, the inter-symbol interference (ISI) has been occurred at the receiver and it can provide the diversity gain. To fully achieve the transmit diversity gain, the maximum likelihood sequence estimation (MLSE) is used at the receiver. It is significant that cyclic-shift allows the use of the Viterbi algorithm (VA) for the MLSE. Hence, the resulting complexity of the receiver is reasonable. From computer simulations, in comparison to the case of single transmit antenna (i.e., no transmit diversity), it has been observed that there is about 3 dB (SdB) signal-to-noise ratio (SNR) gain at a bit error rate (BER) of 10^-2 when 2 (resp., 4) transmit antennas are employed, respectively. Furthermore, the SNR gain increases with decreasing the target BER.