Subband Adaptive Array for Space-Time Block Coding

Future mobile communications is required to provide data transmission with higher rates and more reliability than current systems. As a solution to this problem, the diversity transmission using Alamouti’s space time block coding (STBC)[1] has been adopted in several wireless standard due to its attractive features such as full spatial diversity at full transmission rate. Usually, it requires channel state information (CSI) at the receiver but in [2], whose authors have proposed an adaptive beamforming scheme for Alamouti-type STBC which does not require the explicit CSI for coherent decoding at the receiver. This scheme achieves high performance in a flat fading (FF) channel with co-channel interferences (CCIs), but it cannot applied for the frequency selective fading channel (FSF). Tapped delay line adaptive array (TDLAA)[4] is well known as a solution for this problem since it utilizes the delayed signals to enhance the desired signal instead of excluding them as interferences. However, this method required a large computional load compared to conventional adaptive array system. In this paper, in order to improve the performance of STBC in multipath frequency selective fading channel, we propose a combined transmission scheme of Alamouti’s space-time encoding and subband adaptive array (SBAA) processing. In order to improve the performance of STBC-SBAA, cyclic prefix (CP) is also introduced.