New technique for estimating and suppressing narrowband interference in DSSS systems

A generalized approach for narrowband interference (NBI) suppression in direct sequence spread spectrum (DSSS) communication systems using adaptive infinite impulse response (IIR) filter is presented. The excision filter coefficients depend on both the jammer power and its instantaneous frequency. The dependency of the filter construction on the jammer power is significant as it allows optimal tradeoff between interference removal and signal distortion by maximizing the receiver signal to noise ratio improvement (SNRI). Instead of traditional adaptive line enhancer (ALE) estimator, a preferable NBI estimator-Fourier interpolation estimator (FIE) is proposed. Closed-form expressions of the SNR improvement and theoretical bit error rate (BER) based on the assumption that the output of the correlator is Gaussian distributed are both derived. Performance results obtained by numerical simulation are also presented and compared with theoretical results.