Joint active and passive beamforming for multi-UE communication and extended target detection in IRS-assisted ISAC systems

Author Identifier (ORCID)

Wei Ni: https://orcid.org/0000-0002-4933-594X

Abstract

Intelligent reflecting surface (IRS)-assisted integrated sensing and communications (ISAC) systems have been extensively studied to meet higher sensing requirements. For detection-oriented IRS-assisted ISAC problems, most studies have overlooked the detection interference caused by clutters and modeled simplified point-like targets. This paper investigates extended target detection in IRS-assisted ISAC systems within clutters. We present an optimal generalized likelihood ratio test detector and derive the corresponding probability of detection (PD) and probability of false alarm in closed form. Then, we jointly optimize the active and passive beamforming of the base station and IRS to maximize the PD under multi-user equipment (UE) communication rate constraints and the total transmit power constraint. We first simplify the complex objective function by proving the invariant property of a subspace projection matrix. We then present a novel alternating optimization (AO)-based algorithm to decouple the original problem into two subproblems, consequently convexified and solved using the semidefinite relaxation method. Simulations demonstrate the convergence of the proposed algorithm. The PD performance and the communication and sensing trade-off are significantly improved, compared to benchmarks.

Keywords

Generalized likelihood ratio test (GLRT), integrated sensing and communications (ISAC), intelligent reflecting surface (IRS), probability of detection, probability of false alarm

Document Type

Journal Article

Date of Publication

1-1-2026

Volume

25

Publication Title

IEEE Transactions on Wireless Communications

Publisher

IEEE

School

School of Engineering

Funders

National Natural Science Foundation of China (42171404, 62271352) / Shanghai Engineering Research Center for Blockchain Applications and Services (19DZ2255100) / Fundamental Research Funds for the Central Universities (22120250094)

Comments

Zhang, H., Liu, E., Zhang, S., Xia, S., Ni, W., Wang, R., Xing, Z., Niyato, D., & Jamalipour, A. (2026). Joint active and passive beamforming for multi-UE communication and extended target detection in IRS-Assisted ISAC systems. IEEE Transactions on Wireless Communications, 25, 11577–11592. https://doi.org/10.1109/TWC.2026.3659648

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First Page

11577

Last Page

11592

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Link to publisher version (DOI)

10.1109/TWC.2026.3659648