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Pinching Antennas for Multiple Access in Multigroup Multicast Communications

Shan Shan, Chongjun Ouyang, Yong Li, Yuanwei Liu

TL;DR

Numerical results demonstrate that the pinching-antenna system (PASS) architecture significantly outperforms traditional fixed-antenna systems and NOMA consistently outperforms TDMA-PM and, in high transmit power regimes with heterogeneous multicast group distributions, can even surpass the performance achieved by TDMA-PS.

Abstract

This paper aims to design multiple access (MA) schemes to improve the max-min fairness (MMF) for pinching antennas (PAs)-based multigroup multicast communications, where PA placement and resource allocation are jointly optimized. Specifically, three MA schemes are considered to facilitate the multicast transmission: i) treating interference as noise (TIN), ii) non-orthogonal multiple access (NOMA), and iii) time-division multiple access (TDMA) with two PA reconfiguration protocols, namely pinching switching (PS) and pinching multiplexing (PM). i) For TIN, a closed-form solution is derived for optimal power allocation, while a sequential element-wise optimization (SEO) is developed for the PA placement. ii) For NOMA, a recursive power allocation framework incorporating a bisection search is developed, and a hierarchical objective evaluation (HOE) mechanism is incorporated to simplify the SEO process for PA location update. iii) For TDMA, the PS protocol allows the PA locations to be optimized separately using the SEO method, after which the time-power allocation is solved as a convex problem with a global optimum. Under the PM protocol, the PA locations are jointly optimized with the time-power resources through a Karush-Kuhn-Tucker (KKT)-based analytical solution. Numerical results demonstrate that: i) the pinching-antenna system (PASS) architecture significantly outperforms traditional fixed-antenna systems. ii) TDMA-PS achieves superior performance by fully leveraging the flexible PA reconfiguration and benefiting from interference-free transmission, whereas TIN serves as a practical lower-bound solution due to its simplicity despite its limited performance. iii) NOMA consistently outperforms TDMA-PM and, in high transmit power regimes with heterogeneous multicast group distributions, can even surpass the performance achieved by TDMA-PS.

Pinching Antennas for Multiple Access in Multigroup Multicast Communications

TL;DR

Numerical results demonstrate that the pinching-antenna system (PASS) architecture significantly outperforms traditional fixed-antenna systems and NOMA consistently outperforms TDMA-PM and, in high transmit power regimes with heterogeneous multicast group distributions, can even surpass the performance achieved by TDMA-PS.

Abstract

This paper aims to design multiple access (MA) schemes to improve the max-min fairness (MMF) for pinching antennas (PAs)-based multigroup multicast communications, where PA placement and resource allocation are jointly optimized. Specifically, three MA schemes are considered to facilitate the multicast transmission: i) treating interference as noise (TIN), ii) non-orthogonal multiple access (NOMA), and iii) time-division multiple access (TDMA) with two PA reconfiguration protocols, namely pinching switching (PS) and pinching multiplexing (PM). i) For TIN, a closed-form solution is derived for optimal power allocation, while a sequential element-wise optimization (SEO) is developed for the PA placement. ii) For NOMA, a recursive power allocation framework incorporating a bisection search is developed, and a hierarchical objective evaluation (HOE) mechanism is incorporated to simplify the SEO process for PA location update. iii) For TDMA, the PS protocol allows the PA locations to be optimized separately using the SEO method, after which the time-power allocation is solved as a convex problem with a global optimum. Under the PM protocol, the PA locations are jointly optimized with the time-power resources through a Karush-Kuhn-Tucker (KKT)-based analytical solution. Numerical results demonstrate that: i) the pinching-antenna system (PASS) architecture significantly outperforms traditional fixed-antenna systems. ii) TDMA-PS achieves superior performance by fully leveraging the flexible PA reconfiguration and benefiting from interference-free transmission, whereas TIN serves as a practical lower-bound solution due to its simplicity despite its limited performance. iii) NOMA consistently outperforms TDMA-PM and, in high transmit power regimes with heterogeneous multicast group distributions, can even surpass the performance achieved by TDMA-PS.
Paper Structure (45 sections, 4 theorems, 75 equations, 7 figures, 3 algorithms)

This paper contains 45 sections, 4 theorems, 75 equations, 7 figures, 3 algorithms.

Table of Contents

  1. Introduction
  2. Related Works
  3. Motivations and Contributions
  4. Organization and Notations
  5. System Model
  6. Signal Transmission Model
  7. TIN Scheme
  8. NOMA Scheme
  9. TDMA Scheme
  10. Max-Min Fairness Problem Formulation
  11. TIN-Based Transmission
  12. Optimal Power Allocation Strategy
  13. Sequential Element-Wise PA Location Optimization
  14. NOMA-Based Transmission
  15. Two-Group Multicast Scenario
  16. ...and 30 more sections

Key Result

Lemma 1

For a fixed PA placement vector $\mathbf{x}$, the optimal MMF power allocation policy $\mathbf{p}^{\star}$ under the TIN scheme is given in a closed form. Specifically, the optimal equalized TIN SINR for each group can be written as follows: and the optimal transmit power allocated to the $g$th group is

Figures (7)

  • Figure 1: Illustration of the PASS-enabled multigroup multicast system and the associated multiple access strategies.
  • Figure 2: Convergence behavior of the proposed optimization algorithms in terms of the multicast rate with $N=10$, $G=4$, $K=12$, $D_{\rm x}=20$ m, and $P_{\rm t}=-10$ dBm.
  • Figure 3: Multicast rate versus the transmit power under the random group distribution with $N=10$, $G=4$, $K=12$, $D_{\rm x}=20$ m.
  • Figure 4: Multicast rate versus the transmit power under the heterogeneous group distribution with $N=10$, $G=4$, $K=12$, $D_{\rm x}=20$ m.
  • Figure 5: Multicast rate versus the side length $D_{\rm x}$ with $N=10$, $G=3$, $K=12$, and $P_{\rm t}=-10$ dBm.
  • ...and 2 more figures

Theorems & Definitions (4)

  • Lemma 1
  • Lemma 2
  • Lemma 3
  • Lemma 4