Impact of discrete phase shifts on RIS-enabled covert communications

Author Identifier (ORCID)

Shihao Yan: https://orcid.org/0000-0002-4586-1926

Abstract

This work examines covert communication performance gain achieved by deploying a reconfigurable intelligent surface (RIS) with discrete phase shifts under the scenarios with and without direct transmission links. To this end, we first derive the average receive signal power at the receiver Bob and the warden Willie as functions of the RIS number of elements N and the number of bits d for its discrete phase shift quantization level. Our analytical results reveal that Bob's average power is proportional to N24d, while Willie's average power is proportional to N and does not depend on d. These findings provide clear design guidelines for optimizing RIS configurations to improve covert performance via increasing N or d. To explicitly quantify the performance gain, we analyze the transmission outage probability from the transmitter Alice to Bob and Willie's minimum total detection error probability, which allows us to optimally design Alice's transmit power via minimizing the transmission outage probability subject to the covertness constraint established based on Willie's detection performance, offering practical insights for covert system implementation. Our results also demonstrate that a low-resolution RIS (e.g., d=3) can achieve covert communication performance that is very close to that of an ideal RIS with infinite phase resolution, highlighting the practical value of deploying low-resolution RIS in covert communication systems.

Document Type

Journal Article

Date of Publication

1-1-2025

Publication Title

IEEE Transactions on Vehicular Technology

Publisher

IEEE

School

School of Science

Comments

Zhang, J., Ren, P., Yan, S., Xu, W., Sun, J., & Al-Dhahir, N. (2025). Impact of discrete phase shifts on RIS-enabled covert communications. IEEE Transactions on Vehicular Technology. Advance online publication. https://doi.org/10.1109/TVT.2025.3603211

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Link to publisher version (DOI)

10.1109/TVT.2025.3603211