Interference suppression receiver with adaptive antenna array for code division multiple access communication systems

Combining multiuser receivers with antenna arrays has been proposed to provide spatial discrimination between users based on their respective spatial signature and reduce the Multiple Access Interference (MAI) [1, 2]. These receivers will improve a Code Division Multiple Access (CDMA) communication system performance by a combination of the temporal and spatial filtering. While the adaptive antenna array suppresses interfering signals with arrival angles different from that of the desired user, the multiuser receivers suppress or cancel interfering signals whose arrival angles are the same as that of the desired user. Recently an interference suppression receiver for a CDMA communication system was proposed to suppress MAI [3, 4]. This receiver only uses temporal information of the received signals. Adding an antenna array to this receiver to enhance the performance of this receiver is the idea behind this dissertation. A receiver structure combining an adaptive antenna array and interference suppression receiver structure is introduced. A Direction-Of-Arrival (DOA) tracking algorithm, which maximizes the output power of the antenna array for the desired user signal, is proposed. Simulation results are given to support the analyses.; The major contributions in this dissertation are the proposal of a receiver structure which can improve the system performance in [3, 4] and an adaptive DOA tracking algorithm for CDMA communication systems employing antenna arrays. By using the proposed simple operations, the antenna array can track the DOA of the desired user under Additive White Gaussian Noise (AWGN) and Rayleigh fading environments. The algorithm only needs the first order statistics of the interfering signal and noise. No matrix operation is required during the tracking of the desired user's DOA. Hence the algorithm is simple and has less computation burdens per snapshot. Also the DOA tracking algorithm is not sensitive to the mixer phase distortions. A separate array calibration is not required. Hence, the system employing the DOA tracking algorithm has a lower complexity. Simulation results show the performance improvement of the proposed receiver structure and verify the effectiveness of the proposed DOA tracking algorithm.