Space-time spreading in downlink of TD-SCDMA systems

The paper studies the problems of applying space-time spreading (STS) to the downlink of TD-SCDMA systems under multiusers and multipaths, and evaluates performance of the TD-SCDMA systems under the complicated conditions. In our design, the mobile user in TD-SCDMA systems is only with one omni-directional antenna, keeping the current standard, while at base station, each the transmitted the mobile user's data has been divided two substreams and be sent to two transmitter antennas of the base station. Since the substreams of reaching the mobile user are orthogonal each other in space and time, the system performances (BER and SINK) can be improved much. The paper analyzes the performance of TD-SCDMA systems theoretically and experimentally for under such conditions of multiusers and multipaths. The simulation results show that the TD-SCDMA systems can be of better performance than the conventional CDMA systems based on single transmitted antenna at a base station.