Centralized decision feedback adaptive combined space-time detector for CDMA systems

An adaptive combined array and multiuser detector (spatial and temporal) structure for direct sequence code division multiple access (DS-CDMA) has been proposed in Legnain et al. (1998) to combat co-channel interference and increase the capacity for cellular CDMA. The structure uses a 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 in Abdulrahman et al. (1994) and Miller (1995) in-terms of capacity and near far resistance. In this paper we propose a new centralized decision feedback space-time receiver, which feeds back the detected symbols for all users through a FIR filter without respreading the detected symbols. The focus in this paper is the co-channel interference rejection capability of this structure. Analysis of the optimum tap weights and the minimum mean square error in multipath (no fading) channels are provided, and comparison between this structure and other structures are also provided.