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Distributed Uplink Rate Splitting Multiple Access (DU-RSMA): Principles and Performance Analysis

Apostolos A. Tegos, Yue Xiao, Sotiris A. Tegos, George K. Karagiannidis, Panagiotis D. Diamantoulakis

TL;DR

This work introduces distributed uplink rate-splitting multiple access (DU-RSMA) for a two-RRH, two-user uplink with an error-free feedback link that allows RRHs to share decoded messages. By assigning each user’s messages to the best RRH via a proposed SINR-based selection rule and leveraging the RSMA decoding order $(x_{1a}, x_b, x_{2a})$, the authors derive closed-form ergodic-rate expressions for both users and the system, as well as outage probabilities for fixed-rate operation. A novel fill-factor metric FF_q quantifies the capacity-region squareness, and results show that DU-RSMA with feedback expands the ergodic rate region and improves proportional fairness compared with DU-NOMA and RSMA without feedback, with no OP floor observed for fixed rates. Numerical results validate the analytical expressions and demonstrate the significant impact of distances, path loss, and SNR on performance, supporting the practical potential of DU-RSMA in dense uplink scenarios. Overall, the paper provides theoretical and practical insights into how RRH cooperation via feedback can enhance uplink capacity regions and reliability in 6G-like networks.

Abstract

One of the main goals of the upcoming sixth-generation (6G) wireless networks is the ability to support higher network density, while ensuring a high quality of service for each user. In this paper, we introduce distributed uplink rate-splitting multiple access (DU-RSMA), define its basic principles, and provide insights into its advantages. Specifically, a system with two remote radio heads (RRHs) and two users is investigated. To improve the performance of the system, we consider that the RRHs can communicate through a feedback link, and thus they are able to decode the received messages either independently or with the assistance of the other RRH, since the decoded information can be shared through the feedback link. It should be noted that this scheme increases the achievable capacity region compared to the known multiple access schemes, which is also evaluated by a novel metric termed ``fill factor''. Both the case of adaptive transmission rates and the case of fixed transmission rates are investigated. To this end, the ergodic rate is investigated to cover the former case, while the outage probability is studied for the latter. Closed-form expressions are derived for both metrics. Finally, the analytical expressions are validated by simulation results, which explicitly show the impact of each parameter on the performance of the system, and prove that the proposed scheme outperforms the corresponding benchmarks.

Distributed Uplink Rate Splitting Multiple Access (DU-RSMA): Principles and Performance Analysis

TL;DR

This work introduces distributed uplink rate-splitting multiple access (DU-RSMA) for a two-RRH, two-user uplink with an error-free feedback link that allows RRHs to share decoded messages. By assigning each user’s messages to the best RRH via a proposed SINR-based selection rule and leveraging the RSMA decoding order , the authors derive closed-form ergodic-rate expressions for both users and the system, as well as outage probabilities for fixed-rate operation. A novel fill-factor metric FF_q quantifies the capacity-region squareness, and results show that DU-RSMA with feedback expands the ergodic rate region and improves proportional fairness compared with DU-NOMA and RSMA without feedback, with no OP floor observed for fixed rates. Numerical results validate the analytical expressions and demonstrate the significant impact of distances, path loss, and SNR on performance, supporting the practical potential of DU-RSMA in dense uplink scenarios. Overall, the paper provides theoretical and practical insights into how RRH cooperation via feedback can enhance uplink capacity regions and reliability in 6G-like networks.

Abstract

One of the main goals of the upcoming sixth-generation (6G) wireless networks is the ability to support higher network density, while ensuring a high quality of service for each user. In this paper, we introduce distributed uplink rate-splitting multiple access (DU-RSMA), define its basic principles, and provide insights into its advantages. Specifically, a system with two remote radio heads (RRHs) and two users is investigated. To improve the performance of the system, we consider that the RRHs can communicate through a feedback link, and thus they are able to decode the received messages either independently or with the assistance of the other RRH, since the decoded information can be shared through the feedback link. It should be noted that this scheme increases the achievable capacity region compared to the known multiple access schemes, which is also evaluated by a novel metric termed ``fill factor''. Both the case of adaptive transmission rates and the case of fixed transmission rates are investigated. To this end, the ergodic rate is investigated to cover the former case, while the outage probability is studied for the latter. Closed-form expressions are derived for both metrics. Finally, the analytical expressions are validated by simulation results, which explicitly show the impact of each parameter on the performance of the system, and prove that the proposed scheme outperforms the corresponding benchmarks.

Paper Structure

This paper contains 16 sections, 4 theorems, 80 equations, 6 figures, 8 tables.

Table of Contents

  1. Introduction
  2. Literature Review
  3. Motivation and Contribution
  4. Structure
  5. Proposed Protocol and Achievable Rate Region
  6. Ergodic Rate Analysis
  7. ER of User $a$
  8. ER of User $b$
  9. Outage Analysis
  10. OP of User $a$
  11. OP of User $b$
  12. Numerical Results and Simulations
  13. Conclusions
  14. Proof of Theorem \ref{['th3']}
  15. Proof of Theorem \ref{['th1']}
  16. ...and 1 more sections

Key Result

Theorem 1

In the proposed scheme, the ER of user $a$ is given by where the expressions for $\Bar{C}_{1a}^i$ is provided at the beginning of the next page and The expressions for $\Bar{C}_{1a}^j$ and $\Bar{C}_{2a}^j$ are derived by changing $i$ to $j$ in Ergodic 1A and Ergodic 2A, respectively, where $\mathrm{Ei}(\cdot)$ denotes the exponential integral function gradshteyn2014table. $P_1$ denotes the proba

Figures (6)

  • Figure 1: System model.
  • Figure 2: Capacity region.
  • Figure 3: ER vs transmit SNR.
  • Figure 4: Achievable ergodic capacity region.
  • Figure 5: Outage vs $\alpha$.
  • ...and 1 more figures

Theorems & Definitions (4)

  • Theorem 1
  • Theorem 2
  • Theorem 3
  • Theorem 4