Narrowband interference rejection in direct-sequence spread-spectrum system using time-frequency decomposition

The paper presents a novel method of enhancing the interference rejection capability of a direct-sequence spread-spectrum system. The method is based on performing a frequency analysis of the received signal using a simple filter bank structure in such a way that the temporal information in the input signal is retained. A thresholding algorithm is used to suppress the interference by detecting its frequency and time localisation. This scheme is thus well suited for handling stationary as well as nonstationary interference, without resorting to traditional adaptive algorithms. The method does not affect the receiver performance when interference is not present and works particularly well for strong narrowband interference. Monte Carlo simulation results are given in terms of the bit error rate (BER) against (E_b/N₀) for both stationary and nonstationary interference, and a comparison is made with transform domain processing