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Non-linear methods for group-blind multiuser detection: synchronous case

This paper considers the problem of multiuser detection for CDMA systems where the codes of a group of users are known while others are unknown, called group-blind multiuser detectors. An example is the uplink in cellular communication system with interference from both in-cell users, with known codes, and out-of-cell users, with unknown codes. In previous papers linear detectors for this situation were developed. In the current paper, we combine these methods with low-complexity non-linear post processing, using the method of slowest descent, a general method for non-linear optimization. The performance of this new group-blind detector is compared to that of the non-blind MMSE detector as well as the linear group blind detector, and the non-linear detector is seen to have a considerably better performance, in particular in heavily loaded systems.