Performance Analysis of Space-Time Spreading DS-CDMA Systems over Fast-Fading General Time-Correlated Channels

This paper examines the performance of the space-time spreading (STS), DS-CDMA in a fast-fading general time-correlated Rayleigh channel. The transmitter employs two orthogonal codes to space-time spread the incoming symbols and generates STS symbols for transmission from two transmit antennas over a frequency flat channel. We present an analytical study of the performance of such system when the channel is rapidly varying from one symbol to another and show that it depends on the channel time correlation coefficient. A closed form expression for the probability of bit error as a function of the channel correlation and the input signal to noise ratio is also derived, showing that it increases as the channel correlation increases for a given signal-to-noise ratio. As expected, a lower bound on the bit error rate (BER) is achieved when the channel varies independently from one symbol to another while the upper bound is achieved when the channel is quasi-static. The analytical results depict total agreement with the simulation results.