A hypothesis-test technique for narrowband interference suppression in spread spectrum systems

A method for improved narrowband interference suppression in direct sequence spread spectrum systems is proposed. The method is based on testing hypotheses for the transmitted data bits. Under each hypothesis, an adaptive interference estimate is made and subtracted from the received signal prior to despreading. The final bit decision is made in favor of the hypothesis which results in the least squared error of the estimated data bit. In this manner, the task of providing the interference estimator with the value of the transmitted signal and the task of bit detection are accomplished simultaneously. By using the hypothesized values of the transmitted signal instead of feeding back temporary chip decisions, the problem of unreliable decisions, as well as the problem of delay, inherent in conventional decision feedback interference suppression methods, is eliminated. The algorithm performance is evaluated in simulation and compared to a number of conventional techniques. Results demonstrate better performance than both linear and several decision feedback methods based on both hard and soft decisions.