A hybrid SIC/PIC detector based on a reduced network of kalman filters for DS-CDMA systems over multipath fading channels

A Network of Kalman Filters (NKF)-based detector has recently been proposed for joint Multiple Access Interference (MAI) and Inter-Symbols Interference (ISI) compensation in DS-CDMA systems [1][2][3]. It is based on a symbol state space representation of the DS-CDMA system. The NKF-based detector presents an exponential complexity in term of the Kalman filters (Q(K) where Q represents the number of points in the symbol constellation and K represents the number of active users in the system). In this paper, we propose to linearize the number of Kalman filters used in the aformentioned structure by combining a hybrid SIC/PIC structure and a reduced Network of Kalman Filters-based on a reduced state space representation of the DS-CDMA system. The proposed structure involves two steps. The first, called forward step, decodes the users in a serial approach using a SIC structure. The second, called backward step, is based on a hybrid SIC/PIC structure in order to produce better estimates of the transmitted symbols. The new resulting structure based on a reduced forward-backward NKF detector employs 2(K - 1)Q Kalman filters. It exhibits better performances than the well known existing SIC-RAKE receiver especially in channels with a large delay spread.