INTERFERENCE REJECTION WEIGHT CONTROL FOR PILOT SYMBOL-ASSISTED COHERENT MULTISTAGE INTERFERENCE CANCELER USING RECURSIVE CHANNEL ESTIMATION IN DS-CDMA MOBILE RADIO

To further increase the capacity of the DS-CDMA reverse-link, this pap er investigates the effectiveness of interference rejection weight con trol (IRWC) for the pilot symbol-assisted coherent multistage interfer ence canceller (PSA-COMSIC) using recursive channel estimation (RCE). First, a bit error rate (BER) expression of the serial (successive) an d parallel type hard decision multistage interference canceller (MSIC) with IRWC using Gaussian approximation for multiple access interferen ce (MAI) are presented for no fading channels. It is theoretically sho wn that IRWC is effective in mitigating the interference replica gener ation error in hard decision MSIC. Next, the BER performance of PSA-CO MSIC using IRWC in a multipath Rayleigh fading channel when channel co ding is applied is evaluated by computer simulations. The BER performa nce and capacity are evaluated not only for the conventional serial an d parallel types but also for serial/parallel (S/P) hybrid type and no n-linear/linear (N/L) hybrid type schemes, both of which are effective in significantly reducing the demodulation processing delay. The simu lation results demonstrate that, in interference-limited channels wher e the back ground noise is negligible, the capacity of serial type PSA -COMSIC using IRWC is about 10% higher than that without IRWC. It is a lso found that if we can accept a slight capacity degradation compared to the serial type PSA-COMSIC, S/P hybrid schemes are effective in re ducing the demodulation processing delay.