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

An antenna array is applied to a multiple access interference (MAI) suppression receiver to filter out the interfering signals that are spatially separated from the desired user. Also a novel adaptive direction-of-arrival (DOA) tracking algorithm is introduced under the assumption that the desired signal power is large enough compared to each of the interfering signals at the receiver after the PN despread. The adaptive DOA tracking algorithm requires only the first order statistics of the MAI and additive white Gaussian noise (AWGN). No matrix operation is required. Hence, the tracking algorithm is simple and has a low computational burden. Only 2M multiplications and 2(M-1) additions are required per snapshot for M number of antenna elements. Simulation results in a binary phase shift keying (BPSK) communication system with MAI suppression receiver under AWGN and Rayleigh fading environments are provided to show the tracking capability of the proposed tracking algorithm and the performance improvement of the proposed system.