A fuzzy logic system for interference rejection in code division multiple access

1 This work has been supported by Spanish Government Grants: TIC 2002-04594-C02-01, FIT-070000-2000-649 and the Spanish-French joint collaboration HF 2001-0055. AbstractThe spread spectrum modulation presents a more robust interference rejection capability than the non code-based modulations. However, the increasing of the communication services has augmented the power of the interference signals. In particular, the unlicensed bands such as the Industrial Scientific and Medical (ISM) can seriously saturate the interference rejection capability of the spread spectrum systems. To overcome this drawback it is possible to resort to an Interference Canceller (IC) previously to the detection. Then to design an IC the Conditional Mean (CM) and the Maximum-APosteriori criteria are the optimum methods to suppress analog and digital interferences respectively. However, in general both criteria present a high computational burden which reduces their real feasibility. In addition, the communication scenery can be corrupted by Gaussian or Non-Gaussian noise, which makes more complex the structure of the optimum detector. This paper proposes an interference canceller based on Fuzzy Logic and set theory that allows to suppress either analog or digital interferences and reduces the computational burden of the CM estimator and MAP detector.