Abstract: A low-complexity joint channel estimation and a decoding algorithm for the space-time block coded orthogonal frequency division multiplexing (STBC-OFDM) system in unknown channels is presented. Different from the decoding via exhaustive searching in the previous iterative maximum-likelihood (ML) receiver, in the new algorithm, the signals are estimated analytically, and then are quantized with the aid of the finite alphabet information. The proposed iterative algorithm only involves linear processing and exploits the special orthogonal structure of the STBC-OFDM signal. For a system with two receive antennas, if the Alamouti STBC and 8-PSK signal are adopted, the proposed method has 1／16 the complexity compared with the searching method. As the system complexity increases, the new method has more advantages over the searching method. Simulation results show that our method only has a little performance loss. On the other hand, by simulation, two applications of the new method on time-varying channel tracking and improving the performance of the system with an inserted pilot are given.

Key words: space-time block code, orthogonal frequency division multiplexing, iterative maximum likelihood receiver