QoS-Based Transmit Beamforming in the Presence of Eavesdroppers: An Optimized Artificial-Noise-Aided Approach

• Main Authors: Liao, Wei-Cheng, 廖唯誠
• Other Authors: Chi, Chong-Yung
• Format: Others
• Language: en_US
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/02128414811402630231

碩士 === 國立清華大學 === 通訊工程研究所 === 98 === Secure signal transmission techniques have been receiving growing attention in recent years, as a powerful lternative to blocking eavesdropping attempts in an open wireless medium. This thesis proposes a secure transmit beamforming approach whose goal is to simultaneously enhance an ntended receiver's quality-of-service (QoS) and degrade eavesdroppers' QoSs. Specically, we establish design formulations that i) constrain the maximum allowable signal-to-interference-and-noise ratios (SINRs) of the eavesdroppers; and that ii) provide the intended receiver with a satisfactory SINR through either a guaranteed SINR constraint or SINR maximization. The proposed designs incorporate articial noise (AN), where a suitable amount of AN is added in the transmitted signal to degrade the eavesdroppers' interception. Unlike existing AN-aided designs where the use of AN is usually not optimized, our designs advocate joint optimization of the transmit beamforming weights and AN spatial distribution in accordance with the channel state information (CSI) of the intended receiver and eavesdroppers. Our formulated design problems are nonconvex, and they are shown to be NP-hard in general. We handle the design problems by semidenite relaxation (SDR). We prove that SDR can exactly solve the design problems for a practically representative class of problem instances. Extensions to the per-antenna power constraint case and a challenging multiple intended receivers case are also examined. Simulation results illustrate that the proposed AN-aided designs can yield signicant power savings or SINR enhancement over their no-AN counterparts.