Multirate weighted multistage PIC receiver for UMTS FDD uplink

In this paper, a multirate implementation of a weighted PIC (parallel interference cancellation) receiver, suitable for UMTS base stations is presented. Two key points of this receiver are the calculation of the set of weights for the system, and the technique to regenerate the channels at each stage. The calculation of the set of weights for the systems is based on the eigenvalues of the correlation matrix of the active users. To this end, two approaches for the calculus of the correlation matrix of the UMTS signal are presented. Relative to the regeneration of the channels, three methods are tested: linear regeneration, hard tentative decision and soft tentative decision. For the regeneration methods, in which the amplitude of the channels is needed, we propose a technique to estimate the channel amplitude using all the data received during a scrambling code period. The performance of the proposed receiver is compared against other commonly employed receivers like the adaptive MMSE receiver and the correlation receiver.