Adaptive interference suppression for CDMA based PCN systems

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Abstract
A number of different techniques for the suppression of narrowband interference due to overlay in code division multiple access (CDMA) systems have previously been studied. The relative performances of three such techniques for a fading channel, multi-user CDMA system are described. Personal communication network systems using suppression filters based on the transversal least mean square (LMS) and the lattice and transform domain algorithms are studied. Bit error rates are found by simulations for different suppression filters. The overlay signal is assumed to be narrowband binary phase shift keying (BPSK) and the performance of these systems is studied for varying BPSK carrier frequency offsets. Since both the lattice and LMS filters converge to the Wiener filter, their relative performance is also studied during the on/off transient of the interference. It is found that the LMS and recursive least square (RLS) perform similarly under stationary interference. The RLS is less susceptible to changes in the interference due to its faster convergence.