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BER Analysis and Optimization of Pinching-Antenna-Based NOMA Communications

Mahmoud AlaaEldin, Amy S. Inwood, Xidong Mu, Michail Matthaiou

Abstract

This paper presents the first bit error rate (BER) analysis of a pinching-antenna (PA)-based non-orthogonal multiple access (NOMA) communication system. The PA is assumed to be able to be placed anywhere along the waveguide and serves two NOMA user equipment (UEs) in both uplink (UL) and downlink (DL) scenarios. Exact closed-form expressions for the average BER of each user are derived under practical imperfect successive interference cancellation (SIC). These expressions are then used to optimize the PA location for minimizing the overall average BER of both UEs. In the UL case, the interference between the users' channels introduces phase-dependent fluctuations in the BER cost function, making it highly non-convex with many local extrema. To address this challenge, a smoothing technique is applied to extract the lower envelope of the BER function, effectively suppressing ripples and enabling a reliable identification of the global minimum. In the DL case, a joint optimization of the PA location and NOMA power allocation coefficients is proposed to minimize the average BER. Simulation results verify the accuracy of the analytical derivations and the effectiveness of the proposed optimization methods. Notably, the UL results demonstrate that an optimally positioned PA can create the required received power difference between two equally powered UEs for reliable power-domain NOMA decoding under imperfect SIC.

BER Analysis and Optimization of Pinching-Antenna-Based NOMA Communications

Abstract

This paper presents the first bit error rate (BER) analysis of a pinching-antenna (PA)-based non-orthogonal multiple access (NOMA) communication system. The PA is assumed to be able to be placed anywhere along the waveguide and serves two NOMA user equipment (UEs) in both uplink (UL) and downlink (DL) scenarios. Exact closed-form expressions for the average BER of each user are derived under practical imperfect successive interference cancellation (SIC). These expressions are then used to optimize the PA location for minimizing the overall average BER of both UEs. In the UL case, the interference between the users' channels introduces phase-dependent fluctuations in the BER cost function, making it highly non-convex with many local extrema. To address this challenge, a smoothing technique is applied to extract the lower envelope of the BER function, effectively suppressing ripples and enabling a reliable identification of the global minimum. In the DL case, a joint optimization of the PA location and NOMA power allocation coefficients is proposed to minimize the average BER. Simulation results verify the accuracy of the analytical derivations and the effectiveness of the proposed optimization methods. Notably, the UL results demonstrate that an optimally positioned PA can create the required received power difference between two equally powered UEs for reliable power-domain NOMA decoding under imperfect SIC.
Paper Structure (16 sections, 30 equations, 6 figures)

This paper contains 16 sections, 30 equations, 6 figures.

Table of Contents

  1. Introduction
  2. System Model
  3. Uplink scenario
  4. Downlink scenario
  5. Uplink and Downlink BER Analysis
  6. Uplink scenario
  7. BER Analysis of UE 1
  8. BER Analysis of UE 2
  9. Downlink scenario
  10. BER minimization-based optimization of the PA-based NOMA system
  11. Optimization of the UL scenario
  12. Optimization of the DL scenario
  13. Numerical Results
  14. UL PA-Based NOMA
  15. DL PA-based NOMA
  16. ...and 1 more sections

Figures (6)

  • Figure 1: A -based communication system with two users.
  • Figure 2: Residual interference vectors $r = s_1 - \hat{s}_1$, drawn from the transmitted symbol $s_1$ (origin) to the detected symbol $\hat{s}_1$ (endpoint).
  • Figure 3: of each and the average in the two user -assisted system for both optimized and non-optimized PA placement.
  • Figure 4: Average in dB as a function of position.
  • Figure 5: of each in a two-user -based system for both optimized and non-optimized PA placement and power control coefficients.
  • ...and 1 more figures