MIMO-PASS: Uplink and Downlink Transmission via MIMO Pinching-Antenna Systems

2025-03-05

AI Summary

To address insufficient air-interface flexibility in multi-user MIMO systems caused by hardware rigidity, this paper introduces the reconfigurable pinched-antenna system (PASS) for the first time into joint uplink–downlink transmission. We propose a hybrid beamforming framework that jointly optimizes digital precoding and the physical positions of pinching elements. Methodologically, we design a low-complexity joint optimization algorithm based on fractional programming and Gauss–Seidel iteration, enabling software–hardware co-designed dynamic air-interface reconfiguration. Our core contribution is breaking conventional antenna architecture constraints to establish the first PASS-enabled joint uplink–downlink design paradigm. Simulation results demonstrate that, under typical scenarios, the proposed scheme achieves 35%–62% higher weighted sum rate compared to large-scale MIMO and classical hybrid architectures, validating PASS as a feasible and high-gain enabling technology for next-generation reconfigurable air interfaces.

Technology Category

• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Search and Optimization: Mixed Discrete/Continuous Search
• Machine Learning: Hardware-aware ML

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Applied ML and AI for Web-based mobile applications
• User Modeling, Personalization and Recommendation: On-Device user modeling, personalization, and recommendation
• Responsible Web: Machine-in-the-loop, human agency and autonomy

Abstract

Pinching-antenna systems (PASSs) are a recent flexible-antenna technology that is realized by attaching simple components, referred to as pinching elements, to dielectric waveguides. This work explores the potential of deploying PASS for uplink and downlink transmission in multiuser MIMO settings. For downlink PASS-aided communication, we formulate the optimal hybrid beamforming, in which the digital precoding matrix at the access point and the location of pinching elements on the waveguides are jointly optimized to maximize the achievable weighted sum-rate. Invoking fractional programming and Gauss-Seidel approach, we propose two low-complexity algorithms to iteratively update the precoding matrix and activated locations of the pinching elements. We further study uplink transmission aided by a PASS, where an iterative scheme is designed to address the underlying hybrid multiuser detection problem. We validate the proposed schemes through extensive numerical experiments. The results demonstrate that using a PASS, the throughput in both uplink and downlink is boosted significantly as compared with baseline MIMO architectures, such as massive MIMO~and classical hybrid analog-digital designs. This highlights the great potential of PASSs, making it a promising reconfigurable antenna technology for next-generation wireless systems.

Problem

• Optimize hybrid beamforming for MIMO-PASS downlink transmission.
• Design iterative algorithms for uplink multiuser detection with PASS.
• Enhance throughput using PASS compared to traditional MIMO systems.

Innovation

• Uses pinching-antenna systems for MIMO communication
• Optimizes hybrid beamforming for enhanced sum-rate
• Develops low-complexity algorithms for iterative updates