Performance of C-filter based adaptive spread spectrum receiver in non-Gaussian channels

Abstract

The performance of an adaptive spread spectrum receiver based on the combination filter (C-filter) in the presence of multiuser interference and impulsive channel noise is investigated. For many years, the problem of single user detection in multiuser impulsive channels has been addressed through the use of heuristics in an attempt to reduce the influence of outlying observations. This approach, however ad hoc it may be, is still adopted by many researchers, for reasons of simplicity. C-filters provide an alternative approach in which robust extraction of the desired user signal under both multiuser interference and impulsive noise can be constructed. The C-filters exploit both rank order and temporal order information of the observation sequence to produce the output. They essentially combine the affractive features of both linear FIR and nonlinear filters of the order statistics type. The retention of the temporal order of the observation sequence is essential for the structure of multiuser interference to be learnt adaptively, while the rank order information is useful for removing outliers. The authors evaluate the performance of the C-filter receiver via extensive computer simulations, and it is shown that substantial improvement in performance can be achieved with C-filters over linear filters when the noise exhibits long-tailed distributions.