Reduced-rank space-time adaptive processing for navigation receivers based on QR decomposition and approximations of basis functions

This paper presents a novel reduced-rank space-time adaptive processing (STAP) algorithm for GPS receivers with low computational complexity for protection against the multipath and jamming interferences. The proposed STAP algorithm is based on the least-squares (LS) criterion. The main novelties are the design of the projection matrix based on a set of basis-functions and the derivation of a QR decomposition based reduced-rank recursive LS (QRD-RLS) algorithm for practical implementations. The proposed scheme works on an instantaneous basis, i.e. at each time instant, we select the most suitable set of basis functions to minimize the squared error. Simulation results in a GPS system show that, compared to existing reduced-rank and full-rank algorithms, the proposed algorithm has a much lower computational complexity, and a remarkably better performance for interference suppression and for combating the numerical instability encountered in finite wordlength implementations.