Iterative Coded Multiuser Detection using LDPC Codes

D. Xu and C. D'Amours (Canada)


Iterative Multiuser Detection, Error Control Coding, Interference Cancellation, CDMA


In this paper, the performance of low-density parity check (LDPC) coded multiuser CDMA system is investigated. Multiuser detection (MUD) and LDPC decoding are combined to improve the performance. The soft output of the LDPC decoder is fed back to the multiuser detector to improve the detection. This leads to detection variables that have a reduced multiple access interference (MAI) component. These decision variables are then returned to the decoder. Due to the soft information exchange, both the multiuser detector and the LDPC decoder outputs can be continuously improved. Therefore, the iterative MUD and decoding can achieve a substantial performance gain over separate detection and decoding. Three iterative soft-input soft-output (SISO) multiuser detectors are presented. They are soft interference cancellation detector, soft-input soft-output de-correlating detector and SISO MMSE detector. The performance comparison is also provided.

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