Convergence behaviour of linear parallel cancellation in CDMA

In this paper, the convergence behaviour of linear parallel interference cancellation is investigated. Especially the so-called ping-pong effect where the bit error rate performance is found to oscillate between two different convergence patterns is studied in detail. This effect is shown to be a direct consequence of the extreme eigenvalues of the correlation matrix, allowing for an analytical approach. Intervals for the dominating eigenvalues within which ping-pong effects can occur are specified and illustrated by examples. Relaxation factors, leading to weighted cancellation, are shown to be effective for alleviating oscillations and ping-pong effects at the expense of convergence rate.