Multi-user decoder assisted code-acquisition in CDMA systems

This paper focuses on interference cancellation techniques to improve performance of code-acquisition in code-division multiple access systems. We propose a decoder-aided technique with parallel interference cancellation to overcome multiple access interference in order to detect weak users in a near-far environment. In particular, we consider the case where interference is cancelled after a certain number of multiuser decoder iterations. Time offset of weak user is estimated using a single user synchronization algorithm with interference cancelled received signal, treating residual interference as noise. The probability of missed detection is considered as a measure of performance. We analyze the performance improvement of code-acquisition with number of decoder iterations using the extrinsic information transfer chart of the decoder.