Transmit diversity for arrays with correlated Rayleigh fading

Most transmit diversity systems proposed for the third generation (3G) cellular standard, is designed for the rich scattering environment of indoor or micro-cellular environments where the receiver receives independently Rayleigh faded signals from each of the transmit antenna. We consider the case where the signal is spread over a small angular area, such as outdoors, and the resulting fading from the antenna elements are not necessarily independent. By exploiting prior knowledge of the statistics of this fading environment we propose to transmit only in the direction of the mobile, thereby maximizing the performance. We present a performance analysis of a simple space time code (STC) transmit diversity system, as well as for the new STC beamformer system which is optimized for dense urban cellular environments. We present closed form expressions for the probability of error, SNRO, SIRO and SINRO for these systems.