Efficient detection of space time block codes in time-selective channels via Adaptive Sphere Decoder

In this paper we consider symbol detection in Alamouti´s space-time block coding (STBC) scheme by using adaptive sphere decoder (ASD) which carries out adaptive radius search over time-selective fading channels. Once the channel is time-varying in nature, the channel co-efficients vary from one signaling interval to another, a conventional maximum likelihood (ML) detector carries out exhaustive search and thus becomes computationally expensive specially for higher modulation schemes in a multi-antenna system. Use of SD in time-selective fading channel results in optimal performance with moderate computational complexity. We evaluate the bit-error rate (BER) performance of ASD as compared to the exhaustive search ML detector as well as the generalized simplified ML (GSML) detector, proposed by Tran et al. over time-varying channels. Simulation results suggest that the use of ASD algorithm based on Fincke and Pohst method improves system performance but at expense of marginal computational complexity.