ADAPTIVE IIR FILTERS FOR SINGLE INTERFERENCE SUPPRESSION IN A BPSK DS CDMA SYSTEM IN RAYLEIGH FADING CHANNEL

Abstract

In this paper, effect of a single narrow-band interference (NBI) on bit error rate (BER) performance for a binary phaseshift keying (BPSK) synchronous direct-sequence code-division multiple access (DS CDMA) communication systemoperating in a frequency nonselective Rayleigh fading channel is analyzed. Second-order adaptive infinite impulseresponse (IIR) notch filters with plain gradient algorithm (GA) for suppression of NBI in the DS CDMA system areproposed. A general closed-form BER expression for the DS CDMA system with NBI suppression second order adaptiveIIR notch filters is derived based on the standard Gaussian approximation (SGA) method. BER expressions are thenderived for the allpass filter-based adaptive IIR notch filter and adaptive IIR notch filter with constrained poles andzeros, the two structures that are commonly found in literature. It is observed that both adaptive IIR notch filterstructures exhibit comparable BER performance. Extensive computer simulation results are presented to verify theaccuracy and limitations of the analysis.