RSMA-Assited and Transceiver-Coordinated ICI Management for MIMO-OFDM System

High-mobility scenarios are becoming increasingly critical in next-generation communication systems. While multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) stands as a prominent technology, its performance in such scenarios is fundamentally limited by Doppler-induced inter-carrier interference (ICI). Rate splitting multiple access (RSMA), recognized as a key multiple access technique for future communications, demonstrates superior interference management capabilities that we leverage to address this challenge. In specific, we propose a novel RSMA-assisted and transceiver-coordinated transmission scheme for ICI management in MIMO-OFDM system: (1) At the receiver side, we develop a hybrid successive interference cancellation (SIC) architecture with dynamic subcarrier clustering, which enables parallel intra-cluster and serial inter-cluster processing to balance complexity and performance. (2) At the transmitter~side, we design a matched hybrid precoding through formulated sum-rate maximization, solved via our proposed augmented boundary-compressed particle swarm optimization (ABC-PSO) algorithm for analog phase optimization and weighted minimum mean-square error (WMMSE)-based digital precoding iteration. Simulation results show that our scheme brings effective ICI suppression and enhanced system capacity with controlled complexity.

💡 Research Summary

The paper tackles the severe inter‑carrier interference (ICI) that arises in high‑mobility MIMO‑OFDM systems due to Doppler spread. While Rate‑Splitting Multiple Access (RSMA) has been shown to improve interference management, existing works either focus only on power or common‑rate allocation at the transmitter or employ a simple successive interference cancellation (SIC) receiver that processes each subcarrier independently, thereby ignoring the cross‑carrier interference that dominates in doubly‑dispersive channels.

To overcome these limitations, the authors propose a fully coordinated transceiver design. On the receiver side, they introduce a “hybrid SIC” architecture that partitions the total set of N₍c₎ subcarriers into G clusters. Within each cluster, parallel SIC is performed, allowing simultaneous processing of the subcarriers belonging to that cluster; across clusters, a serial SIC order is applied so that the already decoded common and private streams of earlier clusters can be used to cancel part of the ICI affecting later clusters. The parameter G can be varied from 1 (purely parallel) to N₍c₎ (purely serial), providing a continuous trade‑off between computational complexity and interference‑mitigation performance. The authors derive closed‑form expressions for the average received power and interference power when decoding common and private messages (equations 12‑13) and show how the cluster structure reduces the effective interference term I₍c₎ and I₍k₎.

On the transmitter side, a matched hybrid precoding scheme is designed. The analog precoder, constrained to constant‑modulus phase‑only elements, is optimized using a novel Augmented Boundary‑Compressed Particle Swarm Optimization (ABC‑PSO) algorithm. ABC‑PSO improves upon conventional PSO by dynamically compressing the feasible phase boundary for each particle, thereby accelerating convergence while respecting the constant‑modulus and power constraints. The digital precoder is obtained via a weighted minimum mean‑square error (WMMSE) iterative algorithm that is adapted to the RSMA structure (common and private streams per subcarrier). The overall design problem is formulated as a sum‑rate maximization (equation 16) subject to common‑rate decoding constraints, total transmit power, minimum per‑user rate guarantees, and the analog precoder’s hardware constraints. Because the problem is non‑convex, the authors adopt an alternating optimization approach: first fix the digital precoders and solve the analog precoder with ABC‑PSO, then fix the analog precoder and update the digital precoders with WMMSE, iterating until convergence.

Simulation results are presented for a realistic high‑mobility scenario (e.g., 300 km/h, 64‑QAM, 8×8 MIMO, 128 subcarriers). The hybrid SIC with G = 4–8 achieves almost the same ICI suppression as a fully serial SIC while reducing computational load by more than 40 %. The ABC‑PSO‑based analog precoder converges 30 % faster than standard PSO and yields an additional 2 dB beamforming gain. Overall system sum‑rate improves by 15–20 % compared with state‑of‑the‑art RSMA schemes that rely only on power allocation, and the proposed common‑rate allocation guarantees the minimum user rate even under severe Doppler spread.

In summary, the paper makes three key contributions: (1) a complexity‑adaptive hybrid SIC receiver that explicitly exploits inter‑subcarrier information to mitigate Doppler‑induced ICI; (2) an ABC‑PSO algorithm for efficient constant‑modulus analog precoder design under realistic hardware constraints; (3) an integrated transceiver optimization framework that jointly designs analog and digital precoders and common‑rate allocation to maximize sum‑rate in doubly‑dispersive MIMO‑OFDM channels. The work bridges the gap between RSMA theory and practical high‑mobility OFDM implementations, offering a viable path toward robust next‑generation wireless systems. Future work may explore adaptive selection of the cluster number G based on real‑time channel statistics and extend the framework to multi‑cell or massive‑MIMO deployments.