New adaptive combined space-time receiver for multiuser interference rejection in synchronous CDMA systems

New adaptive combined array and multiuser detector (spatial and temporal) structure for direct sequence code division multiple access (DS-CDMA) is proposed to combat co-channel interference and increase the capacity for cellular CDMA. The structure uses an L-sensor (element) linear array. Each element is followed by a chip matched filter (CMF) and a fractionally-spaced adaptive equalizer. The proposed structure outperforms the conventional receiver and the structures proposed by Abdulrahman, Sheikh and Falconer (see IEEE JSAC, vol.12, no.4, p.698-706, 1994) and by Miller (see IEEE Tran. Comm., vol.43, no.2/3/4, p.1746-55, 1995) in terms of the capacity and near far resistance. The proposed structure can also operate in heavy traffic channels with many users having the same angle of arrival (AOA) as the desired user, while the conventional array can not. Analysis of the optimum weights and the minimum mean square error in the synchronous DS-CDMA channel is provided, and comparison between this structure and the structures proposed by Abdulrahman et al. and by Miller are also provided.