Compatible improvement of the GSM/EDGE system by means of space-time coding techniques

On the basis of the GSM/EDGE system, the application of space-time coding techniques is investigated, especially with regard to aspects of compatibility with current specifications. In this paper, simple special cases of space-time trellis codes and space-time block codes are considered, namely the delay-diversity and the Alamouti scheme. The performance improvements obtainable by means of these techniques in the case of a typical urban (TU) wireless channel are demonstrated both on the basis of analytical and simulation results. For the delay-diversity scheme, a lower bound on the bit-error probability is derived and an optimization of the intrinsic delay parameter is considered. For the Alamouti scheme, a novel trellis-based soft-output equalization and detection algorithm is presented, which is of same complexity as in the single transmit antenna case. Moreover, in the case of the Alamouti scheme, appropriate training sequence pairs are required. In this context, optimized partner sequences with respect to the eight GSM sequences are introduced yielding pairs that significantly outperform any pair of GSM sequences. Furthermore, the sensitivity of the delay-diversity and the Alamouti scheme to a time-variant TU channel is addressed as well as to nonperfect knowledge of the channel coefficients at the receiver.