Adaptive fuzzy interference cancellation for CDMA communication systems

This paper proposes a new application of fuzzy inference mechanism to the interference cancellation in a direct-sequence code-division multiple-access (DS/CDMA) communication system over a non-perfect power control channel. Multistage parallel interference cancellation (PIC) is an effective method to cancel the multiple access interference (MAI) for equal-power channels; nevertheless, there is a significant degradation in performance for non-equal power ones. The effectiveness of interference cancellation is related to the reliability of the tentative decision involved in the interference estimates. We established a fuzzy logic system to adapt the weight of each interference cancellation path. According to the received signal´s reliability, the weights of interfering users can be estimated by the fuzzy inference mechanism, so that the error propagation would be minimized. The simulation results show that the proposed adaptive fuzzy PIC scheme is robust to the interference and channel noise and is superior to the conventional PIC and constant weight PIC schemes under a severe near-far environment