Research On Adaptive Narrowband Suppression Techniques In Spread Spectrum Communication Systems

As is well known, this inherent coding gain and processing gain determine the interference rejection capability. In fact, any level of interference protection can be obtained by designing the signal with sufficient processing gain. It is difficult for the DSSS system to ensure a high quality of communication only by its processing gain when the interference-to-signal overruns the interference tolerance. Therefore, the research of suppressing interferences in spread spectrum system has great theoretical and practical significance.On the basis of the theories of spread spectrum communication systems and narrowband interference suppression, this paper improves the narrow-band interference suppression in transform domain based on adaptive multi-threshold algorithm, applies the adaptive filtering algorithms in the narrow-band interference suppression. These algorithms are simulated in the data transmission systems.(1) This paper solves its bad performance by introducing coefficient of variation when noise-to-signal is high,based on the analysis of narrow-band interference suppression in transform domain based on adaptive multi-threshold algorithm. The algorithm has better practicability by introducing coefficient of variation.(2) A fraction clip process is derived based on the frequency domain adaptive filtering algorithm. The frequency-domain algorithms of narrow-band interference based on is designed and simulated by uniting coefficient of variation and fraction clip.(3) The variable step-size LMS algorithm used arc tangent function improves convergence speed and suppression performance by introducing coefficient of variation which can be carried out in project. The method for suppressing low-bandwidth interference in DSSS was proposed with simulation results.(4) These algorithms are simulated in the data transmission systems. Simulation showed that these algorithm have good performance in suppressing narrowband interference in the data transmission system. The interference tolerance of the data transmission system is not under 20dB when the bit of rate is 10-5.