Robust Distributed Beamforming Design in Amplify-and-forward Relay Systems with Multiple User Pairs

• Main Authors: Hsieh, Pei-Wen, 謝沛彣
• Other Authors: Chen, Sau-Gee
• Format: Others
• Language: en_US
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/16055964271541214984

碩士 === 國立交通大學 === 電子工程學系 電子研究所 === 101 === Distributed beamforming is an effective technique for spatial multiplexing in relay systems with multiple user pairs. The optimization of distributed beamforming requires the channel state information (CSI). However, perfect CSI is not available in practice. Therefore, a robust design is required to reduce the effects of CSI errors. Quality-of-service (QoS) is a popular design criterion for distributed beamforming which aims to minimize transmit power while satisfying the QoS criterion. In this thesis, we propose new approaches for signal-to-interference- plus-noise ratio (SINR)-based QoS robust distributed beamforming in amplify- and-forward (AF) one-way relay systems with multiple user pairs. We derive new bounds for the worst-case received signal power and interference power. The proposed new bounds are tighter than the bounds derived by the Cauchy-Swartz inequality in [18]. Besides, the proposed new bounds have a specific quadratic structure, which enables the originally non-convex robust optimization problem to be approximated as a convex semidefinite programming (SDP) problem or a convex second-order cone (SOCP) programming problem. The simulation results show that the proposed SDP-based method and the proposed SOCP method both outperform the existing SDP-based methods in terms of transmit power. Besides, the proposed SOCP-based method has lower computational complexity than the existing SDP-based methods. In addition, we investigate the robust max-min SINR design which optimizes the max-min SINR under the power constraint. The robust max-min SINR design problem is converted to a series of robust SINR-based QoS design problem using the bisection searching technique. The robust SINR-based QoS design problem in each bisection iteration is solved by the proposed SDP-based method or the proposed SOCP-based method. Finally, we generalize the distributed beamforming design to two-way AF relay systems. We apply the proposed methods to solve the design problems with and without physical layer network coding (PLNC). The simulation results show that our methods with PLNC improve the system throughput greatly.