Space-Time Coding Scheme for Forward Link Multiuser STBC-OFDM Systems

In forward link multiuser space-time block coded orthogonal frequency division multiplexing (STBC-OFDM) systems, the signal-to-noise power ratio (SNR) of each user´s received signal is different from those of others. Thus, when subcarriers are not properly allocated to users, intensive bit errors occur in a specific user. This causes a burst error in such a user, and the number of correctable bits decreases. As a result, the bit error rate (BER) performance of the overall system is degraded. In this paper, we propose a space-time coding scheme which distributes bit errors among users. In our coding scheme, by letting several users share a subcarrier, bit errors are distributed among users. Therefore, our coding scheme prevents the occurrence of intensive bit errors. Simulation results show that the BER performance of the system using our coding scheme with two or three transmit antennas is better than that of the system with the conventional coding scheme even when proper subcarrier allocation schemes are not employed.