Interference Suppression with L1-Norm Constraint for Satellite Navigation Systems

Abstract

Currently, there have been many studies of interference suppression for satellite navigation systems. Power minimization approach is an effective interference suppression algorithm. It forms automatically deep nulls in the DOAs (direction of arrival) of interferences without prior information about the DOAs of satellite signals and interferences. However, the power minimization approach can not provide flat gains in other directions. Thus there will be fluctuation in the beampattern, especially when the number of snapshots is not enough. It means that the desired satellite signal may be partly suppressed when they locate in the shallow nulls. In this paper, by combining eigenvalue thresholding method and l1-norm constraint, we propose a new interference suppression algorithm to suppress interferences and provide flat gains in all directions except that of interferences. The difference between the new algorithm and the conventional power minimization approach lies in the improvement of covariance matrix which is constituted based on the main eigenvalues and corresponding eigenvectors of covariance matrix. In addition, an explicit l1-norm constraint on the beam gains is exploited to provide flat gain in all directions except that of interferences. When there are interferences and spoofing, the spoofing is generally suppressed heavier than the authorized signal. It will decrease the power difference between the spoofing and authorized signals. Thus it will degrade the performance of subsequent spoofing detection. So the proposed algorithm also can be applied to the spoofing detection in satellite navigation systems. The simulations demonstrate the effectiveness of the proposed algorithm.