A matrix-algebraic approach to linear hybrid interference cancellation in CDMA

In this paper we consider a matrix algebraic approach to a linear hybrid interference canceller (HIC). This scheme is a combination of parallel and successive cancellation. It is shown that both the single-stage and multistage linear HIC can be expressed as a one-shot linear matrix filter on the received chip-matched filtered signal vector. It is proved that if the linear HIC converges, it will converge to the decorrelating detector. The eigenvalue conditions for the convergence of the multistage schemes are then derived. It is shown by simulation that the linear HIC with four or more groups at every stage can converge. When there are only two groups, however, the detector may not always converge. In this case, a weighted cancellation structure is suggested to ensure convergence. Simulation results show that if the detector converges, the minimum BER is generally obtained before the convergence is achieved, and that the weighted structure has smaller minimum BER than the non-weighted one