Computing partial cancellation factors for PPIC receiver in large CDMA over a fading channel

Abstract

In this paper, we introduce a simple, closed-form expression for finding the optimum partial cancellation factors (PCF) for the linear multistage partial parallel interference cancellation (PPIC) receiver. These factors are found in a direct- sequence code division multiple access (DS-CDMA) system over a frequency-flat fading channel for a large-system case. In this case, the number of active users and the processing gain tend to infinity while their ratio is finite. It will be shown that the expression for the PCF is a function of the moments of the eigenvalues of the correlation matrix, the number of interference cancellation (IC) stages, the system load, and the signal-to-noise ratio (SNR). Compared to recently-proposed methods, our method has the following advantages: a) It is less complex because the calculated PCF will be a direct function of the moments of the eigenvalues of the large correlation matrix; b) there is no need for ordering the PCF resulting in lower complexity; and c) it is not necessary to know the number of IC stages ap riori .