Wideband Millimeter-Wave Beam Training with True-Time-Delay Array Architecture

TL;DR

This paper introduces a one-shot beam training method for millimeter-wave systems using true-time-delay arrays, significantly reducing training overhead by exploiting frequency-dependent beam steering.

Contribution

It proposes a novel beam training technique leveraging TTD arrays for efficient, low-overhead angular scanning in millimeter-wave communications.

Findings

Requires an order-of-magnitude fewer training symbols than phased arrays.

Enables high-resolution propagation direction estimation.

Uses a single OFDM symbol for entire angular domain scanning.

Abstract

Millimeter-wave communications rely on beamforming gain from both transmitters and receivers to compensate for severe propagation loss. To achieve adequate gain, beam training is required to identify propagation directions. The main challenge in beam training arises from maintaining low overhead with increased array size. This paper presents a novel one-shot beam training technique that utilizes the emerging architecture of true-time-delay (TTD) arrays. We first show that TTD arrays facilitate frequency dependent beam steering. The proposed training procedure with TTD arrays then exploits this fact by using a single radio-frequency-chain to multiplex different subcarriers into different sounding directions. We derive conditions on the parameters of TTD array configuration and physical layer to achieve scanning of the entire angular domain with a single orthogonal frequency-division multiplexing (OFDM) training symbol. The estimation of propagation directions with high resolution is achieved via low-complexity digital signal processing of spatially coded subcarriers. Simulation results show that this TTD array based approach requires an order-of-magnitude fewer training symbols than those of phased arrays.