Abstract
The intelligent reflecting surface (IRS), which consists of a large number of reflecting units, can adjust the phase shifts of its reflecting units to strengthen the desired signal and/or suppress the undesired signal. In this paper, we consider an IRS-assisted wireless surveillance system where an IRS is deployed to assist the legal surveillance receiver E to monitor the information transmission of the suspicious link from AP to the suspicious receiver B. Two communication scenarios assuming whether the suspicious link is aware of the existence of the monitor are considered. The optimization problem under the constraint that the achievable rate at the monitor E is larger than that at the suspicious receiver B is proposed to jointly optimize the beamforming vector at the AP and the phase shift matrix at the IRS to maximize the achievable eavesdropping rate. To solve this non-convex problem, we introduce the semi-definite relaxation (SDR) approach and the alternating optimization (AO) method to convert the non-convex optimization problem to a series of semi-definite programs (SDPs) and solve the SDPs iteratively. Simulation results show that the assistance of IRS can greatly improve the performance of the surveillance, and achieves significant advantages over the traditional relay-assisted wireless surveillance system.
Highlights
The fifth-generation (5G) wireless communication networks have been applied in commercial deployment [1]
To solve the non-convex optimization problems, we introduce the semi-definite relaxation (SDR) method and alternating optimization (AO) approach to convert the original optimization problem to a series of semi-definite programs (SDPs) which are solved iteratively
Active beamforming and passive beamforming are optimized jointly to maximize the achievable rate of intelligent reflecting surface (IRS)-assisted surveillance systems by SDR and alternating optimization techniques
Summary
The fifth-generation (5G) wireless communication networks have been applied in commercial deployment [1]. It aims at realizing ultra-high spectrum and energy efficiency, ultra-dense user connectivity, and very low latency. Due to the open nature of the wireless medium, the security problem presents a great threat to the information transmission in the wireless communication systems. The legal surveillance of suspicious information transmission is a very urgent need. The achievable rate of the monitor in the surveillance system should be higher than that of the suspicious receiver such that the information from the suspicious transmitter could be decoded successfully at the monitor [2]
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