Iterative multiuser detection and decoding for highly correlated narrowband systems and heavily loaded CDMA systems

When a soft-in soft-out (SISO) iterative multiuser detector cooperates with a bank of SISO single-user decoders, the multiuser system performance can be shown to converge to that of the single-user system. In this paper, a novel SISO iterative detector which employs a decorrelator on the output of soft interference cancellation is proposed. By making use of the advantages of decorrelating detection, the performance of the proposed system is improved with only a small complexity increase compared with pure soft interference cancellation. The performance improvement is reflected in lower bit error rates at low signal-to-noise ratios and in the higher convergence speed. Therefore, the proposed iterative detector is especially suitable for highly correlated narrowband systems and heavily loaded code-division multiple access (CDMA) systems. Both performance analysis and simulation results are providedto show this improvement. Finally, the computational complexity of the detector is analyzed.