Abstract

In dynamic propagation environments, beamforming algorithms may suffer from strong interference, steering vector mismatches, a low convergence speed and a high computational complexity. Reduced-rank signal processing techniques provide a way to address the problems mentioned above. This paper presents a low-complexity robust data-dependent dimensionality reduction based on an iterative optimization with steering vector perturbation (IOVP) algorithm for reduced-rank beamforming and steering vector estimation. The proposed robust optimization procedure jointly adjusts the parameters of a rank reduction matrix and an adaptive beamformer. The optimized rank reduction matrix projects the received signal vector onto a subspace with lower dimension. The beamformer/steering vector optimization is then performed in a reduced dimension subspace. We devise efficient stochastic gradient and recursive least-squares algorithms for implementing the proposed robust IOVP design. The proposed robust IOVP beamforming algorithms result in a faster convergence speed and an improved performance. Simulation results show that the proposed IOVP algorithms outperform some existing full-rank and reduced-rank algorithms with a comparable complexity.

Highlights

  • Adaptive beamforming algorithms often encounter problems when they operate in dynamic environments with large sensor arrays

  • Steering vector mismatches are often caused by calibration/pointing errors, and a high complexity is usually introduced by an expensive inverse operation of the covariance matrix of the received data

  • The candidate steering vectors are responsible for performing rank reduction, and the reduced-rank beamformer forms the beam in the direction of the signal of interest (SoI)

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Summary

Introduction

Adaptive beamforming algorithms often encounter problems when they operate in dynamic environments with large sensor arrays These problems include steering vector mismatches, high computational complexity and snapshot deficiency. The advantage of reduced-rank methods lies in their superior convergence and tracking performance achieved by exploiting the low-rank nature of the signals It offers a large reduction in the required number of training samples over full-rank methods [2], which may addresses the problem of snapshot deficiency at low complexity. In order to address this problem, in this paper, we introduce a low-complexity robust data-dependent dimensionality reduction algorithm for reduced-rank beamforming and steering vector estimation.

System Model
Minimum Variance Distortionless Response
Recursive Least-Squares
Reduced Rank Methods and the Projection Matrix
Problem Statement and the Proposed IOVP
Design Algorithm
Stochastic Gradient Adaptation
Recursive Least-Squares Adaptation
Proposed Robust Capon IOVP Beamforming
Rank Selection
Simulations
Conclusions
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