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Fluid Antenna-Aided Rate-Splitting Multiple Access

Farshad Rostami Ghadi, Kai-Kit Wong, F. Javier Lopez-Martinez, Lajos Hanzo, Chan-Byoung Chae

TL;DR

Numerical results show that combining FAS with RSMA significantly outperforms TAS and conventional multiple access schemes, such as non-orthogonal multiple access (NOMA), in terms of OP, and indicate that FAS can be the tool that greatly improves the practicality of RSMA.

Abstract

This letter considers a fluid antenna system (FAS)-aided rate-splitting multiple access (RSMA) approach for downlink transmission. In particular, a base station (BS) equipped with a single traditional antenna system (TAS) uses RSMA signaling to send information to several mobile users (MUs) each equipped with FAS. To understand the achievable performance, we first present the distribution of the equivalent channel gain based on the joint multivariate t-distribution and then derive a compact analytical expression for the outage probability (OP). Moreover, we obtain the asymptotic OP in the high signal-to-noise ratio (SNR) regime. Numerical results show that combining FAS with RSMA significantly outperforms TAS and conventional multiple access schemes, such as non-orthogonal multiple access (NOMA), in terms of OP. The results also indicate that FAS can be the tool that greatly improves the practicality of RSMA.

Fluid Antenna-Aided Rate-Splitting Multiple Access

TL;DR

Numerical results show that combining FAS with RSMA significantly outperforms TAS and conventional multiple access schemes, such as non-orthogonal multiple access (NOMA), in terms of OP, and indicate that FAS can be the tool that greatly improves the practicality of RSMA.

Abstract

This letter considers a fluid antenna system (FAS)-aided rate-splitting multiple access (RSMA) approach for downlink transmission. In particular, a base station (BS) equipped with a single traditional antenna system (TAS) uses RSMA signaling to send information to several mobile users (MUs) each equipped with FAS. To understand the achievable performance, we first present the distribution of the equivalent channel gain based on the joint multivariate t-distribution and then derive a compact analytical expression for the outage probability (OP). Moreover, we obtain the asymptotic OP in the high signal-to-noise ratio (SNR) regime. Numerical results show that combining FAS with RSMA significantly outperforms TAS and conventional multiple access schemes, such as non-orthogonal multiple access (NOMA), in terms of OP. The results also indicate that FAS can be the tool that greatly improves the practicality of RSMA.

Paper Structure

This paper contains 11 sections, 3 theorems, 24 equations, 1 figure.

Table of Contents

  1. Introduction
  2. System Model
  3. Channel Model
  4. Signal Model
  5. Signal-to-Interference Plus Noise Ratio (SINR)
  6. Performance Analysis
  7. SINR Distribution
  8. OP Analysis
  9. Numerical Results
  10. Conclusion
  11. Proof of Proposition \ref{['pro-dist']}

Key Result

Proposition 1

The CDF and PDF of the equivalent channel gain $g_{\mathrm{fas},k}$ at MU $\mathrm{u}_k$ for FAS-RSMA are given by and where $\overline{g}=\mathbb{E}\left[g\right]$ is the mean of the channel gain, $t_{\nu_k}^{-1}\left(\cdot\right)$ is the inverse CDF (quantile function) of the univariate $t$-distribution having $\nu_k$ degrees of freedom for the $k$-th MU, $T_{\nu_k,\mathbf{\Sigma}_k}\left(\cdo

Figures (1)

  • Figure 1: OP vs. the average transmit SNR $\overline{\gamma}$: (a) for different numbers of fluid antenna ports $N_k$ with a fixed $W_k=1\lambda^2$, and (b) for different values of fluid antenna size with a fixed $N_k=9$.

Theorems & Definitions (6)

  • Proposition 1
  • proof
  • Proposition 2
  • proof
  • Corollary 1
  • proof