ARIS-RSMA Enhanced ISAC System: Joint Rate Splitting and Beamforming Design

This letter proposes an active reconfigurable intelligent surface (ARIS) assisted rate-splitting multiple access (RSMA) integrated sensing and communication (ISAC) system to overcome the fairness bottleneck in multi-target sensing under obstructed line-of-sight environments. Beamforming at the transceiver and ARIS, along with rate splitting, are optimized to maximize the minimum multi-target echo signal-to-interference-plus-noise ratio under multi-user rate and power constraints. The intricate non-convex problem is decoupled into three subproblems and solved iteratively by majorization-minimization (MM) and sequential rank-one constraint relaxation (SROCR) algorithms. Simulations show our scheme outperforms nonorthogonal multiple access, space-division multiple access, and passive RIS baselines, approaching sensing-only upper bounds.

💡 Research Summary

This paper addresses the challenging problem of achieving fair multi‑target sensing in integrated sensing‑and‑communication (ISAC) systems when line‑of‑sight (LOS) paths are blocked. The authors propose a novel framework that jointly exploits an active reconfigurable intelligent surface (ARIS) and rate‑splitting multiple access (RSMA). The ARIS can amplify and phase‑shift incident signals, thereby restoring weak or blocked propagation paths, while RSMA introduces a common data stream that can be decoded by all users, allowing part of the interference to be treated as useful information rather than being completely nulled as in conventional space‑division multiple access (SDMA).

System model: a monostatic base station (BS) equipped with M transmit/receive antennas serves U single‑antenna downlink users and simultaneously illuminates Q sensing targets. An L‑element ARIS is placed to assist the BS‑target links that suffer from blockage. The BS transmits a vector of streams s =