Performance Analysis for Rate Splitting Multiple Access Enhanced Pinching-Antenna Assisted Integrated Sensing and Communication Systems

The novel flexible-antenna technology, known as pinching antennas, has recently attracted significant research interest. By embedding discrete dielectric materials, a pinching antenna can be dynamically activated at arbitrary points along a dielectric waveguide, enabling flexible control of large-scale path loss and on-demand coverage extension. This paper investigates the performance analysis of a downlink rate-splitting multiple access (RSMA) enhanced pinching-antenna assisted integrated sensing and communication (ISAC) system. Specifically, we consider a sensing-centric scenario in which a single pinching antenna simultaneously serves two communication users and performs target sensing, where the sensing target and one user are co-located in the same room and are served via a line-of-sight (LoS) link, while the other user resides in a separate room and is connected through a non-LoS (NLoS) link. We derive novel closed-form expressions for the outage probabilities (OPs) of both communication and sensing tasks. The communication OP is obtained through an information-theoretic approach, whereas the sensing OP is evaluated using a mean square error (MSE) based approach. In addition, the system throughput for the communication task and average sensing MSE for the sensing task are also evaluated. To gain further insights, asymptotic OP expressions are also derived for both communication and sensing tasks in the high signal-to-noise ratio (SNR) regime. Monte Carlo simulations are performed to validate the analytical results. Numerical results demonstrate that the proposed pinching-antenna-assisted RSMA–ISAC system outperforms pinching-antenna-assisted non-orthogonal multiple access (NOMA)–ISAC and space-division multiple access (SDMA)–ISAC in terms of communication reliability and sensing accuracy. Furthermore, compared with a conventional antenna-assisted RSMA–ISAC benchmark, the proposed framework achieves significant sensing performance gains due to reduced effective sensing distance and near-field spatial focusing enabled by pinching antennas, while exhibiting a controllable sensing–communication trade-off governed by power allocation and antenna positioning. Finally, we analyze the impact of pinching-antenna height, room size, and other key system parameters on the performance of both communication and sensing tasks.