Robust Secure Communications in Near-Field ISCAP Systems with Extremely Large-Scale Antenna Array

TL;DR

This paper proposes a robust beamforming strategy for secure near-field ISCAP systems with extremely large-scale antenna arrays, ensuring confidentiality, sensing accuracy, and energy transfer despite imperfect channel information.

Contribution

It introduces a joint beamforming design that maximizes secrecy rate while supporting sensing and energy transfer under CSI uncertainties in ELAA-based ISCAP systems.

Findings

Achieves robust secrecy rate maximization under imperfect CSI.

Develops a low-complexity algorithm for joint beamforming.

Ensures secure communication, sensing, and energy transfer simultaneously.

Abstract

This paper investigates robust secure communications in a near-field integrated sensing, communication, and powering (ISCAP) system, in which the base station (BS) is equipped with an extremely large-scale antenna array (ELAA). In this system, the BS transmits confidential messages to a single legitimate communication user (CU), simultaneously providing wireless power transfer to multiple energy receivers (ERs) and performing point target sensing. We consider a scenario in which both the ERs and the sensing target may act as potential eavesdroppers attempting to intercept the confidential messages. To safeguard secure communication, the BS employs a joint beamforming design by transmitting information beams combined with dedicated triple-purpose beams serving as energy and sensing signals, as well as artificial noise (AN) for effectively jamming potential eavesdroppers. It is assumed that only coarse location information of the ERs and sensing targets or eavesdroppers is available at the BS, leading to imperfect channel state information (CSI). Under this setup, we formulate a robust beamforming optimization problem with the objective of maximizing the secrecy rate for the CU, while ensuring worst-case performance requirements on both target sensing and wireless energy harvesting at the ERs. To address the non-convex robust joint beamforming problem and facilitate the deployment of a low-complexity algorithm, we employ the S-procedure alongside an eavesdropping CSI error-bound determination method to acquire a high-quality solution.