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Performance Analysis of FAS-Aided NOMA-ISAC: A Backscattering Scenario

Farshad Rostami Ghadi, Kai-Kit Wong, F. Javier Lopez-Martinez, Hyundong Shin, Lajos Hanzo

TL;DR

This article investigates a two-user downlink system for integrated sensing and communication (ISAC) in which the two users deploy a fluid antenna system (FAS) and adopt the nonorthogonal multiple access (NOMA) strategy, and confirms the superiority of employing FAS over traditional fixed-position antenna systems in both ISAC and ISABC.

Abstract

This paper investigates a two-user downlink system for integrated sensing and communication (ISAC) in which the two users deploy a fluid antenna system (FAS) and adopt the nonorthogonal multiple access (NOMA) strategy. Specifically, the integrated sensing and backscatter communication (ISABC) model is considered, where a dual-functional base station (BS) serves to communicate the two users and sense a tag's surrounding. In contrast to conventional ISAC, the backscattering tag reflects the signals transmitted by the BS to the NOMA users and enhances their communication performance. Furthermore, the BS extracts environmental information from the same backscatter signal in the sensing stage. Firstly, we derive closed-form expressions for both the cumulative distribution function (CDF) and probability density function (PDF) of the equivalent channel at the users utilizing the moment matching method and the Gaussian copula. Then in the communication stage, we obtain closed-form expressions for both the outage probability and for the corresponding asymptotic expressions in the high signal-to-noise ratio (SNR) regime. Moreover, using numerical integration techniques such as the Gauss-Laguerre quadrature (GLQ), we have series-form expressions for the user ergodic communication rates (ECRs). In addition, we get a closed-form expression for the ergodic sensing rate (ESR) using the Cramer-Rao lower bound (CRLB). Finally, the accuracy of our analytical results is validated numerically, and we confirm the superiority of employing FAS over traditional fixed-position antenna systems in both ISAC and ISABC.

Performance Analysis of FAS-Aided NOMA-ISAC: A Backscattering Scenario

TL;DR

This article investigates a two-user downlink system for integrated sensing and communication (ISAC) in which the two users deploy a fluid antenna system (FAS) and adopt the nonorthogonal multiple access (NOMA) strategy, and confirms the superiority of employing FAS over traditional fixed-position antenna systems in both ISAC and ISABC.

Abstract

This paper investigates a two-user downlink system for integrated sensing and communication (ISAC) in which the two users deploy a fluid antenna system (FAS) and adopt the nonorthogonal multiple access (NOMA) strategy. Specifically, the integrated sensing and backscatter communication (ISABC) model is considered, where a dual-functional base station (BS) serves to communicate the two users and sense a tag's surrounding. In contrast to conventional ISAC, the backscattering tag reflects the signals transmitted by the BS to the NOMA users and enhances their communication performance. Furthermore, the BS extracts environmental information from the same backscatter signal in the sensing stage. Firstly, we derive closed-form expressions for both the cumulative distribution function (CDF) and probability density function (PDF) of the equivalent channel at the users utilizing the moment matching method and the Gaussian copula. Then in the communication stage, we obtain closed-form expressions for both the outage probability and for the corresponding asymptotic expressions in the high signal-to-noise ratio (SNR) regime. Moreover, using numerical integration techniques such as the Gauss-Laguerre quadrature (GLQ), we have series-form expressions for the user ergodic communication rates (ECRs). In addition, we get a closed-form expression for the ergodic sensing rate (ESR) using the Cramer-Rao lower bound (CRLB). Finally, the accuracy of our analytical results is validated numerically, and we confirm the superiority of employing FAS over traditional fixed-position antenna systems in both ISAC and ISABC.
Paper Structure (22 sections, 10 theorems, 57 equations, 7 figures, 1 table)

This paper contains 22 sections, 10 theorems, 57 equations, 7 figures, 1 table.

Table of Contents

  1. Introduction
  2. State-of-the-Art
  3. Motivation and Contributions
  4. Paper Organization
  5. Mathematical Notations
  6. System and Channel Models
  7. System Model
  8. Signal and Channel Models
  9. Communication stage
  10. Sensing stage
  11. SINR Characterization
  12. Performance Analysis
  13. Statistical Characteristics
  14. Communication Performance
  15. OP Analysis
  16. ...and 7 more sections

Key Result

Theorem 1

The CDF of the channel gain $g_{\mathrm{fas},i}$ at the FAS-equipped NOMA user $i$ under correlated Rayleigh fading is given by eq-cdf (see top of this page), in which $\Upsilon\left(x,y\right)$ denotes the lower incomplete gamma function, and where $\overline{a}=\mathbb{E}\left[g^{n_i}_{\mathrm{b},i}\right]$, $\overline{b}=\mathbb{E}\left[g_\mathrm{b,t}\right]$, and $\overline{c}=\mathbb{E}\lef

Figures (7)

  • Figure 1: The system model of ISABC with two FAS-aided users and one backscatter tag.
  • Figure 2: OP versus average SNR $\overline{\gamma}$ for the near user $\mathrm{u_n}$, based on \ref{['eq-out-n']}.
  • Figure 3: OP versus average SNR $\overline{\gamma}$ for the far user $\mathrm{u_f}$, based on \ref{['eq-op2']}.
  • Figure 4: ECR versus average SNR $\overline{\gamma}$ for the near user $\mathrm{u_n}$, based on \ref{['eq-ecr-un']}.
  • Figure 5: ECR versus average SNR $\overline{\gamma}$ for the far user $\mathrm{u_f}$, based on \ref{['eq-ecr-uf']}.
  • ...and 2 more figures

Theorems & Definitions (19)

  • Theorem 1
  • proof
  • Theorem 2
  • proof
  • Theorem 3
  • proof
  • Theorem 4
  • proof
  • Corollary 1
  • proof
  • ...and 9 more