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

TL;DR

This paper investigates constellation-constrained optimization of SIC-free Rate-Splitting Multiple Access (RSMA) for large-scale wireless systems, demonstrating its near-equivalent performance to SIC-based RSMA with reduced complexity.

Contribution

It derives constellation-constrained rate expressions for RSMA, develops scalable optimization algorithms, and evaluates the performance of SIC-free RSMA in large-scale systems.

Findings

SIC-free RSMA achieves comparable sum-rate to SIC-based RSMA.

Proposed algorithms effectively optimize precoders for large systems.

SIC-free RSMA shows minor performance loss, suitable for practical deployment.

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 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 both weighted sum-rate and max-min fairness in comparison to RSMA with SIC receivers, making it a viable option for future implementations.