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Max-Min Fairness for Uplink Rate-Splitting Multiple Access with Finite Blocklength

Jiawei Xu, Yijie Mao

TL;DR

The paper addresses max-min fairness for uplink RSMA in a $K$-user SISO MAC under finite blocklength constraints. It proposes a general RSMA model with selective message splitting, a low-complexity decoding order, and a successive convex approximation based power-allocation algorithm to maximize the minimum user rate under FBL. Key contributions include a convexified optimization framework with convergence guarantees and complexity analysis, plus a comprehensive numerical study showing RSMA yields higher MMF than NOMA and can even surpass IFBL NOMA as the number of splitting users grows. The results highlight RSMA's potential to improve fairness and latency performance in URLLC uplink scenarios, albeit with increased hardware and computational demands as splitting complexity rises.

Abstract

In this letter, we investigate the performance of Max Minimum Fairness (MMF) for uplink Rate-Splitting Multiple Access (RSMA) in short-packet communications. Specifically, considering a Single-Input Single-Output (SISO) Multiple Access Channel (MAC), we optimize the transmit power allocation between the splitting user messages to maximize the minimum rate among users with Finite Blocklength (FBL) constraints. To tackle this problem, we propose a Successive Convex Approximation (SCA)-based approach. Additionally, we introduce a low-complexity scheme to design the decoding order at the receiver. Numerical results show that RSMA outperforms conventional transmission schemes such as Non-orthogonal Multiple Access (NOMA) in terms of MMF.

Max-Min Fairness for Uplink Rate-Splitting Multiple Access with Finite Blocklength

TL;DR

The paper addresses max-min fairness for uplink RSMA in a -user SISO MAC under finite blocklength constraints. It proposes a general RSMA model with selective message splitting, a low-complexity decoding order, and a successive convex approximation based power-allocation algorithm to maximize the minimum user rate under FBL. Key contributions include a convexified optimization framework with convergence guarantees and complexity analysis, plus a comprehensive numerical study showing RSMA yields higher MMF than NOMA and can even surpass IFBL NOMA as the number of splitting users grows. The results highlight RSMA's potential to improve fairness and latency performance in URLLC uplink scenarios, albeit with increased hardware and computational demands as splitting complexity rises.

Abstract

In this letter, we investigate the performance of Max Minimum Fairness (MMF) for uplink Rate-Splitting Multiple Access (RSMA) in short-packet communications. Specifically, considering a Single-Input Single-Output (SISO) Multiple Access Channel (MAC), we optimize the transmit power allocation between the splitting user messages to maximize the minimum rate among users with Finite Blocklength (FBL) constraints. To tackle this problem, we propose a Successive Convex Approximation (SCA)-based approach. Additionally, we introduce a low-complexity scheme to design the decoding order at the receiver. Numerical results show that RSMA outperforms conventional transmission schemes such as Non-orthogonal Multiple Access (NOMA) in terms of MMF.
Paper Structure (5 sections, 10 equations, 5 figures, 1 algorithm)

This paper contains 5 sections, 10 equations, 5 figures, 1 algorithm.

Table of Contents

  1. Introduction
  2. System Model
  3. Problem Formulation and Optimization
  4. Numerical Results
  5. Conclusion

Figures (5)

  • Figure 1: The MMF performance of RSMA, NOMA and TIN versus transmit SNR with four different blocklengths. K=2.
  • Figure 2: The MMF performance of RSMA and NOMA versus blocklengths with three different transmit SNR. K=2.
  • Figure 3: The MMF performance versus transmit SNR of RSMA and NOMA with different numbers of splitting users. K=4. Blocklength=250 bits.
  • Figure 4: Relative MMF rate gain of RSMA compared to NOMA. K=4. Transmit SNR=20dB.
  • Figure 5: The MMF versus the number of users K of RSNMA and NOMA. Transmit SNR=20 dB.