Iterative interference cancellation and decoding using a soft cancellation factor for DS-CDMA

We consider a DS-CDMA system that employs both partial parallel interference cancellation (PIC) and convolutional coding. Information is shared between the operations of interference cancellation and decoding in an iterative manner, using log-likelihood ratios (LLR) of the estimated coded symbols. We investigate the performance of this system for both synchronous and asynchronous CDMA systems, and for both equal and unequal signal powers. Previous work has demonstrated the improved performance of partial parallel interference cancellation in which the interference estimates are weighted by a soft cancellation factor (SCF). We examine the best choice of the SCF for optimizing the combined performance of interference cancellation and coding.