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   Robust Collaborative-Relay BeamformingZheng, Gan  ; ; et alin IEEE Transactions on Signal Processing (2009), 57(8), 3130-3143 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 ... [more ▼] 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. [less ▲] Detailed reference viewed: 173 (2 UL)Collaborative-Relay Beamforming with Perfect CSI: Optimum and Distributed ImplementationZheng, Gan ; ; et alin IEEE Signal Processing Letters (2009), 16(4), 257260 This letter studies the collaborative use of amplify-and-forward (AF) relays to form a virtual multiple-input single-output (MISO) beamforming system with the aid of perfect channel state information (CSI ... [more ▼] This letter studies the collaborative use of amplify-and-forward (AF) relays to form a virtual multiple-input single-output (MISO) beamforming system with the aid of perfect channel state information (CSI) in a flat-fading channel. In particular, we optimize the relay weights jointly to maximize the received signal-to-noise ratio (SNR) at the destination terminal with both individual and total power constraints at the relays. We show that the optimal collaborative-relay beamforming (CRB) solution achieves the full diversity of a MISO antenna system. Another main contribution of this letter is a distributed algorithm that allows each individual relay to learn its own weight, based on the Karush-Kuhn-Tucker (KKT) analysis. [less ▲] Detailed reference viewed: 173 (0 UL)On the Asymptotic Optimality of Opportunistic Norm-based User Selection with Hard SINR Constraint; ; Ottersten, Björn et alin EURASIP Journal on Advances in Signal Processing (2009) Detailed reference viewed: 166 (1 UL)Guaranteed Performance Region in Fading Orthogonal Space-Time Coded Broadcast Channels; Ottersten, Björn ; et alin EURASIP Journal on Wireless Communications and Networking (2008) Detailed reference viewed: 142 (1 UL)Feedback Reduction in Uplink MIMO OFDM Systems by Chunk Optimization; ; Ottersten, Björn et alin EURASIP Journal on Applied Signal Processing (2008) Detailed reference viewed: 136 (0 UL)Feedback Reduction in Uplink MIMO OFDM Systems by Chunk Optimization; ; Ottersten, Björn et alin IEEE International Conference on Communications (ICC) (2008) Detailed reference viewed: 130 (0 UL) |
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