Performance of the improved PIC receiver for DS-CDMA over Rayleigh fading channels

The optimum performance of the improved parallel interference cancellation (PIC) receiver is shown for a DS-CDMA system over Rayleigh fading channels. The improved PIC receiver proposed by Divsalar et al. (see IEEE Trans. Commun., vol.46, no.2, p.258-68, 1998) significantly reduces the degrading effect on the desired user of interference by removing from each user a part of the interference produced by the remaining users accessing the channel the amount being proportional to their reliability. The MMSE estimator, a hyperbolic tangent function, is used as a tentative decision device of the improved PIC receiver for the optimum BER performance. The BER of the improved PIC receiver with the MMSE estimator as a tentative decision device is obtained by simulations and compared with those of the conventional PIC receiver and the improved PIC receiver with a signum function as a tentative decision device. The BER change with respect to the weight factors in the hyperbolic tangent functions is shown for the multi-stage improved PIC receiver. Also, the BER performance in near-far situations and with the channel estimation error is shown over Rayleigh fading channels. From the numerical results, it is shown that the improved PIC receiver with a hyperbolic tangent function achieves remarkable performance improvement over the conventional PIC receiver and the improved PIC receiver with a signum function. It is also shown that the BER of the improved PIC receiver with a hyperbolic tangent function is close to the single-user bound even in the near-far situation