Linear group-wise successive interference cancellation in CDMA

In this paper, we consider a matrix-algebraic approach to linear group-wise successive interference cancellation. As for both successive and parallel cancellation, it is shown that the general linear group-wise scheme corresponds to a one-shot linear matrix filtering. Furthermore, it is shown that if the general structure converges, it converges to the decorrelator. Four structures are considered for the group detector, namely the matched filter, the parallel canceller, the decorrelator and the MMSE detector, and the equivalent one-shot filters are derived. Conditions for convergence related to the grouping are studied and it is shown that group detection with a decorrelator, which has conventional successive interference cancellation as a special case, always converges. Through numerical examples, it is illustrated that the performance for all the structures behaves like the performance for the linear successive canceller where a minimum BER is reached before convergence to the performance of the decorrelator occurs. The matched filter group canceller achieves the lowest minimum BER but also has the slowest convergence.