Performance Comparison of Alamouti Space-Time Coded and Amplify-Forward Relay Diversities for OFDM Signals

Diversity implementation improves the error rate performance of communication systems. Two diversity techniques among various of them are space-time diversity and cooperative diversity. In this study, symbol error rate performances of space-time and cooperative diversities for Orthogonal Frequency Division Multiplexing (OFDM) signals are compared. A simple space-time diversity, Alamouti scheme with two transmitter and one receiver antennas, and a cooperative diversity with single relay amplify-and-forward structure are considered. Both can achieve a transmit diversity order of 2. The considered channel model is a Rayleigh flat fading per carrier frequency due to narrow-band multi-carrier transmitted signal. For modulation technique, phase shift keying (PSK) modulation is used. By using both of diversity techniques, performance results are obtained by theoretically and by simulation for different modulation levels (4, 16 ve 64) of PSK. Results show that the Alamouti scheme achieves better symbol error performance than the single relay cooperative diversity.