Robust collaborative-relay beamforming

  • Authors:

  • Gan Zheng;Kai-Kit Wong;Arogyaswami Paulraj;Björn Ottersten

  • Affiliations:

  • Department of Electronic and Electrical Engineering, University College London, London, WC, U.K.;Department of Electronic and Electrical Engineering, University College London, London, WC, U.K.;Information Systems Laboratory, Stanford University, Stanford, CA;School of Electrical Engineering, Royal Institute of Technology, Stockholm, Sweden and University of Luxembourg, Luxembourg

  • Venue:
  • IEEE Transactions on Signal Processing
  • Year:
  • 2009

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Abstract

Relay communications is a promising technique to extend the range of wireless communications by forwarding the message from the sender to the intended destination. While fixed or variable-power relays have been previously investigated, this paper addresses the collaborative use of variable-phase variable-power amplify-and-forward (AF) relays for robust beamforming, with the aid of imperfect channel state information (CSI) at the sender. In particular, the maximization of the worst-case signal-to-noise ratio (SNR) at the destination terminal is studied under a bounded spherical region for the norm of the CSI error vector from the relays to the destination. Our main contribution is that we prove, under a condition on the quality of the estimated CSI, the robust-optimal collaborative-relay beamforming (CRBF) can be obtained by S-Procedure and rank relaxation techniques. In addition, a distributed algorithm is developed by examining the structure of the optimal CRBF solution. Results demonstrate a significant gain of CRBF over non-robust approaches.