Beam Training for Pinching-Antenna Systems (PASS)

TL;DR

This paper introduces a scalable, multi-stage beam training scheme for pinching-antenna systems across various user scenarios, significantly reducing training overhead and enhancing flexibility and performance.

Contribution

It proposes a novel three-stage beam training scheme with scalable codebooks for different PASS scenarios, improving efficiency and supporting NOMA transmission.

Findings

Reduces training overhead compared to exhaustive search.

Supports NOMA transmission with improved beam training.

Dynamic pinching antennas outperform fixed and conventional arrays.

Abstract

This article investigates the beam training design problems for pinching-antenna systems (PASS), where single-waveguide-single-user (SWSU), single-waveguide-multi-user (SWMU) and multi-waveguide-multi-user (MWMU) scenarios are considered. For SWSU-PASS, we design a scalable codebook, based on which we propose a three-stage beam training (3SBT) scheme. Specifically, 1) firstly, the 3SBT scheme utilizes one activated pinching antenna to obtain a coarse one-dimensional location at the first stage; 2) secondly, it achieves further phase matching with an increased number of activated antennas at the second stage; 3) finally, it realizes precise beam alignment through an exhaustive search at the third stage. For SWMU-PASS, based on the scalable codebook design, we propose an improved 3SBT scheme to support non-orthogonal multiple access (NOMA) transmission. For MWMU-PASS, we first present a generalized expression of the received signal based on the partially-connected hybrid beamforming structure. Furthermore, we introduce an increased-dimensional scalable codebook design, based on which an increased-dimensional 3SBT scheme is proposed. Numerical results reveal that: i) the proposed beam training scheme can significantly reduce the training overhead compared to the two-dimensional exhaustive search, while maintaining reasonable rate performance; ii) compared to fixed-location pinching antennas and conventional array antennas, the proposed dynamic pinching antennas yield better flexibility and improved performance.