Direct Sequence Spread Spectrum Interference Rejection Using Vector Space Projection Techniques

Abstract

A new method of rejecting narrowband interference in direct-sequence spread spectrum communications is presented. A typical approach is to reject the interference using a filter with large attenuation at the interference frequencies prior to despreading. The interference rejection method presented in this paper incorporates vector space projection techniques to suppress the correlated interference. Several signal characteristics are formulated which lead to constraint surfaces in the vector space of possible solutions. These constraint surfaces describe interference rejection solutions which introduce minimal distortion to the chip sequence and simultaneously remove the interference. The constraint surfaces essentially correspond to chip sequence estimates which, after interference rejection, conform to known characteristics of the transmitted chip sequence. The formulation of the surfaces relies on prior knowledge about the chip sequence correlation and spectral properties.

This work was supported by a Harpole-Pentair Faculty Fellowship.