Downlink CDMA systems with space-time codes and interference cancellation

Space-time coding and interference cancellation based on orthogonal projection are powerful techniques to improve the communication quality and capacity in downlink CDMA systems. The space-time encoder output stream is transmitted through the fading channel using multiple transmitter antennas, increasing communication reliability against multipath fading. On the other hand, orthogonal projection-based interference cancellation mitigates the multiuser interference. This is achieved by projecting the received signals to the orthogonal subspace of the interference signal subspace. We propose a method that combines these two techniques. The proposed method allows the downlink CDMA system to be robust against both channel fading and multiuser access interference. Simulation results are provided for both static and dynamic fading channel environments.