Full-rate, full-diversity adaptive space time block coding for transmission over Rayleigh fading channels

A full-rate, full-diversity adaptive space time block coding (ASTBC) scheme based on singular value decomposition (SVD) is proposed for transmission over Rayleigh fading channels. The ASTBC-SVD scheme advocated is capable of providing both full-rate aid full-diversity for any number of transmit antennas, N_t, provided that the number of receive antennas, N_r, equals to N_t. Furthermore, the ASTBC-SVD scheme may achieve an additional coding gain due to its higher product distance with the aid of the block code employed. In conjunction with SVD, the "water-filling" approach can be employed for adaptively distributing the transmitted power to the various antennas transmit according to the channel conditions, in order to further enhance the attainable performance. Since a codeword constituted by N_t symbols is transmitted in a single time slot by mapping the N_t symbols to the N_t transmit antennas in the spatial domain, the attainable performance of the ASTBC-SVD scheme does not degrade, when the channel impulse response values vary from one time slot to the next. Hence, the proposed ASTBC-SVD scheme is attractive in the context of both uncorrelated and correlated Rayleigh fading channels. The performance of the proposed scheme was evaluated, when communicating over uncorrelated Rayleigh fading channels. Explicitly, an E_b/N₀ gain of 2.5 dB was achieved by the proposed ASTBC-SVD scheme against Alamoutrs scheme [S.M. Alamouti, October 1998], when employing N_t = N_r = 2 in conjunction with 8PSK.