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 phase
shift keying (BPSK) synchronous direct-sequence code-division multiple access (DS CDMA) communication system
operating in a frequency nonselective Rayleigh fading channel is analyzed. Second-order adaptive infinite impulse
response (IIR) notch filters with plain gradient algorithm (GA) for suppression of NBI in the DS CDMA system are
proposed. A general closed-form BER expression for the DS CDMA system with NBI suppression second order adaptive
IIR notch filters is derived based on the standard Gaussian approximation (SGA) method. BER expressions are then
derived for the allpass filter-based adaptive IIR notch filter and adaptive IIR notch filter with constrained poles and
zeros, the two structures that are commonly found in literature. It is observed that both adaptive IIR notch filter
structures exhibit comparable BER performance. Extensive computer simulation results are presented to verify the
accuracy and limitations of the analysis.