Iterative multi-user turbo-code receiver for DS-CDMA

The topic of interference cancellation in a coded Code Division Multiple Access (CDMA) system has been the focus of much recent research. Earlier works have studied methods for jointly decoding all the users resulting in most having an exponential complexity for the corresponding receiver. In this report, a number of di erent iterative decoding methods are proposed for the multi-user interference cancellation in a CDMA system where Turbo Codes are utilized for forward error correction. In the proposed decoding schemes, the individual users are decoded separately with the operation of iterative interference cancellation being mixed with the iterative decoding of Turbo Codes. These iterative decoders result in only a marginal increase in the overall complexity as compared to a conventional single user receiver utilizing Turbo Codes for forward error correction. Numerical performance results are presented showing that in the cases of practical interest for CDMA applications, the multiple access interference can be essentially removed at a reasonable level of complexity. These iterative decoders achieve a similar to better performance with a reduction in complexity as compared to similar previously known research work. i