Compatible improvement of the GSM/GPRS system by means of space-time block codes

We investigate the application of the Alamouti space-time block code (STBC) on the basis of the GSM/GPRS system, especially with regard to aspects of compatibility with current specifications. The performance improvements obtainable by means of this technique are demonstrated on the basis of simulation results. A novel trellis-based soft-output equalization and detection algorithm for the Alamouti scheme is presented which is of the same complexity as in the single transmit antenna case. Moreover, appropriate training sequence pairs are derived. In this context, optimized partner sequences with respect to the eight GSM sequences are introduced that significantly outperform any pair of GSM sequences. Analytical results are presented demonstrating the sensitivity of the Alamouti scheme to fast and/or frequency-selective fading as well as to imperfect knowledge of the channel coefficients at the receiver.