SIC-Free Rate-Splitting Multiple Access: Constellation-Constrained Optimization and Application to Large-Scale Systems

2025-06-15

AI Summary

In RSMA systems under finite-alphabet constellations, the successive interference cancellation (SIC) receiver incurs prohibitively high computational complexity. Method: This paper proposes a novel SIC-free RSMA paradigm tailored to finite-constellation constraints. We first derive the theoretical rate bounds for SIC-free RSMA under such constraints; then design a low-complexity projected subgradient algorithm to jointly optimize weighted sum rate and max-min fairness; finally, we introduce an information-theoretic modeling framework incorporating constellation constraints and a large-system approximation technique for computational acceleration. Results: Simulations demonstrate that the proposed scheme achieves performance close to conventional SIC-based RSMA—both in weighted sum rate and fairness—while drastically reducing receiver-side computational complexity. The approach thus offers a viable, efficient multiple-access solution for large-scale, low-overhead wireless communication systems.

Technology Category

• Constraint Satisfaction and Optimization: Constraint Satisfaction
• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Search and Optimization: Mixed Discrete/Continuous Search

Application Category

• Security and Privacy: Large-scale security measurements
• Search and Retrieval-Augmented AI: Efficiency and scalability of Web search engines
• Systems and Infrastructure for Web, Mobile and WoT: Experiences and lessons learnt from Web-based algorithms and system deployments

Abstract

Rate-Splitting Multiple Access (RSMA) has been recognized as a promising multiple access technique for future wireless communication systems. Recent research demonstrates that RSMA can maintain its superiority without relying on Successive Interference Cancellation (SIC) receivers. In practical systems, SIC-free receivers are more attractive than SIC receivers because of their low complexity and latency. This paper evaluates the theoretical limits of RSMA with and without SIC receivers under finite constellations. We first derive the constellation-constrained rate expressions for RSMA. We then design algorithms based on projected subgradient ascent to optimize the precoders and maximize the weighted sum-rate or max-min fairness (MMF) among users. To apply the proposed optimization algorithms to large-scale systems, one challenge lies in the exponentially increasing computational complexity brought about by the constellation-constrained rate expressions. In light of this, we propose methods to avoid such computational burden. Numerical results show that, under optimized precoders, SIC-free RSMA leads to minor losses in weighted sum-rate and MMF performance in comparison to RSMA with SIC receivers, making it a viable option for future implementations.

Problem

• Optimizing RSMA without SIC for low complexity systems
• Deriving constellation-constrained rate expressions for RSMA
• Reducing computational complexity in large-scale RSMA systems

Innovation

• SIC-free RSMA for low complexity systems
• Constellation-constrained precoder optimization algorithms
• Scalable solutions for large-scale wireless systems