Interference Suppression Technique For Direct Sequence Spread Spectrum Communication System

First, some interference mitigation techniques involved adaptive filtering in thetime domain and transform domain processing are discussed in this paper.Additionally, an adaptive time-frequeney exciser used in DSSS system is alsodescribed. Among the transform processing, the real-time discrete Fourier transformalgorithm is not sensitive to the frequency, power and number of interference. Also itcan be easily implemented using the fast Fourier transform in frequency domain. Dueto the advantage of handling fixed and variable multiple interference and adaptingrapidly, the frequency domain technique for narrowband interference suppressionbecomes the focus study of the paper. A new improved narrowband interferencesuppression technique is provided and simulations are performed using MATLAB totest the performance.In succession, we concentrate on performance analysis of DSSS systems'immunity to LFM interference and corresponding suppressing measures. First theinterference suppressing measures in time-frequency (t-f) domain in DSSScommunication systems are summarized. Then, an algorithm for the suppressing ofLFM interference using fractional Fourier transform (FRFT) is proposed. And also anew improved FRFT technique is provided. The performance analyses have shownthat the proposed algorithm distinctly can obtain the better BER performance.Because FRFT can be implemented by FFT, comparing with other filtering algorithmsbased two-dimensional t-f tool, it is easier in computation.