Multistage semi-blind adaptive multiuser detector for reverse link in CDMA systems

We develop a novel multistage semiblind multiuser detection technique for the reverse link in direct sequence (DS) code-division multiple access (CDMA) systems. This approach fully utilizes all known users' information, performs interference cancellation (IC) to suppress the interferers within the cell, and exploits a blind adaptive decision-directed (DD) MMSE detector to suppress the inter-cell interference. This process can be made iterative and in the multistage process, the tentative decision bits from DD-MMSE detectors can be fed back to the IC part to make interference regeneration more accurate. A simplified adaptive algorithm for this multistage semi-blind detectors is designed. Two upper bounds for the signal-to-noise-interference ratio (SIR) of the multistage semiblind detector are derived. It is shown that the proposed detector has a significant performance gain over that of the pure blind detectors and the non-blind detectors. The tracking capability of the proposed semi-blind detector in a dynamic environment is examined with simulations.