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

TL;DR

This work tackles fairness in multi-target sensing for ISAC under obstructed LoS by proposing an active RIS (ARIS) aided RSMA framework. It jointly designs BS transmit/receive beamformers, ARIS reflection, and RSMA rate splitting using a block coordinate descent approach with MM and SROCR to handle non-convexity, achieving a max-min echo SINR across targets while meeting per-user QoS and power constraints. The proposed method outperforms PRIS, NOMA, and SDMA baselines and approaches sensing-only upper bounds, highlighting the value of combining ARIS amplification with RSMA in challenging propagation environments. The approach is practically impactful for robust, fair sensing performance in complex ISAC deployments with blocked LoS.</nobracket>

Abstract

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.

Figures (5)

• Figure 1: Illustration of the ARIS-RSMA ISAC system.
• Figure 2: Max-min SINR vs. $R_{\rm{th}}$.
• Figure 3: Rate allocation vs. $R_{\rm{th}}$.
• Figure 4: Max-min SINR vs. $a_{\rm{max}}$.
• Figure 5: Max-min SINR vs. ARIS location.