SE-EE Tradeoff in Pinching-Antenna Systems: Waveguide Multiplexing or Waveguide Switching?

TL;DR

The paper investigates the spectral-energy efficiency tradeoff in pinching-antenna systems (PASS) under two practical protocols: waveguide multiplexing (WM) and waveguide switching (WS). It formulates a multi-objective optimization to jointly design baseband and pinching beamforming and solves it via the ε-constraint method, revealing distinct SE-EE tradeoffs for WM and WS. WM employs alternating optimization with successive convex approximation and particle swarm optimization to handle coupling between beamformers and PA positions, while WS uses time-division transmission to maximize per-user channel gains followed by power allocation. Results show that WS can achieve higher energy efficiency, WM can reach higher spectral efficiency, and the benefits scale with the number of users and the operating regime (WS benefits notably in low-SNR). The findings provide design guidance for PASS deployments aiming to balance SE and EE in practical wireless networks.

Abstract

The spectral and energy efficiency (SE-EE) trade-off in pinching-antenna systems (PASS) is investigated in this paper. In particular, two practical operating protocols, namely waveguide multiplexing (WM) and waveguide switching (WS), are considered. A multi-objective optimization problem (MOOP) is formulated to jointly optimize the baseband and pinching beamforming for maximizing the achievable SE and EE, which is then converted into a single-objective problem via the ε-constraint method. For WM, the problem is decomposed within the alternating-optimization framework, where the baseband beamforming is optimized using the successive convex approximation, and the pinching beamforming is updated through the particle swarm optimization. For WS, due to the time-division transmission and interference-free nature, the pinching beamforming in each time slot is first adjusted to maximize the served user channel gain, followed by the baseband power allocation. Simulation results demonstrate that 1) PASS outperforms conventional antennas by mitigating large-scale path losses; 2) WS leads to a higher maximum achievable EE by activating a single RF chain, whereas WM yields a higher SE upper bound by serving all users concurrently; and 3) increasing the number of users substantially enhances SE under WM, whereas WS shows more pronounced benefits in low-signal-to-noise ratio regimes.

Figures (4)

• Figure 1: Illustration of a PASS-based wireless communication system.
• Figure 2: Illustration of two practical operating protocols.
• Figure 3: Achievable SE-EE tradeoff versus different $N$.
• Figure 4: Achievable SE-EE tradeoff versus different users.