Ergodic Secrecy Rate of RIS-Assisted Communication Systems in the Presence of Discrete Phase Shifts and Multiple Eavesdroppers

• Published in: IEEE wireless communications letters Vol. 10; no. 3; pp. 629 - 633
• Main Authors: Xu, Peng, Chen, Gaojie, Pan, Gaofeng, Renzo, Marco Di
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 01.03.2021; The Institute of Electrical and Electronics Engineers, Inc. (IEEE); IEEE comsoc
• Subjects: Closed-form solutions; Communication systems; Communications systems; discrete phase shifts; Eavesdropping; Electronics; Engineering Sciences; Ergodic processes; ergodic secrecy rate; Mathematical analysis; multiple eavesdroppers; Reconfigurable intelligent surface; Reconfigurable intelligent surfaces; Scaling laws; Security; Transmitters; discrete phase shifts; multiple eavesdroppers; Reconfigurable intelligent surface; ergodic secrecy rate
• ISSN: 2162-2337; 2162-2345
• DOI: 10.1109/LWC.2020.3044178

This letter investigates the ergodic secrecy rate (ESR) of a reconfigurable intelligent surface (RIS)-assisted communication system in the presence multiple eavesdroppers (Eves), and by assuming discrete phase shifts at the RIS. In particular, a closed-form approximation of the ESR is derived for both non-colluding and colluding Eves. The analytical results are shown to be accurate when the number of reflecting elements of the RIS <inline-formula> <tex-math notation="LaTeX">{N} </tex-math></inline-formula> is large. Asymptotic analysis is provided to investigate the impact of <inline-formula> <tex-math notation="LaTeX">{N} </tex-math></inline-formula> on the ESR, and it is proved that the ESR scales with <inline-formula> <tex-math notation="LaTeX">\log \,_{2} N </tex-math></inline-formula> for both non-colluding and colluding Eves. Numerical results are provided to verify the analytical results and the obtained scaling laws.