STAR-RIS-Assisted Full-Space Angle Estimation via Finite Rate of Innovation

TL;DR

This paper introduces a novel full-space angle estimation framework using STAR-RIS and FRI models, enabling accurate, gridless angle detection in both uniform and nonuniform configurations with low overhead.

Contribution

It develops a comprehensive FRI-based angle estimation method for STAR-RIS that supports full-space detection and includes algorithms for practical signal recovery and angle estimation.

Findings

Achieves reliable full-space angle estimation with low overhead.

Develops a convergence-guaranteed proximal-gradient algorithm for FRI signal recovery.

Demonstrates improved estimation performance across different STAR-RIS configurations.

Abstract

Conventional sensor architectures typically restrict angle estimation to the half-space. By enabling simultaneous transmission and reflection, simultaneously transmitting and reflecting reconfigurable intelligent surfaces (STAR-RIS) can support full-space angle detection. This paper develops a fullspace angle estimation framework by leveraging a finite rate of innovation (FRI) model enabled by STAR-RIS. We distinguish two practical STAR-RIS configurations: (i) an element-wise uniform setting, where all metasurface elements share identical energy-splitting (ES) coefficients and phase differences, and (ii) a nonuniform ES setting, where the phase difference is common across elements while the ES coefficients vary element-wise to increase design flexibility. For each regime, we formulate the corresponding FRI-based signal model and derive the Ziv-Zakai bound (ZZB) for angle estimation. To recover the underlying FRI sampling structure, we develop a proximal-gradient algorithm implemented via alternating projections in matrix space and establish its convergence. Exploiting the recovered FRI structure, we construct an annihilating filter whose zeros encode user angles, enabling gridless estimation via polynomial root finding. Numerical results demonstrate that the proposed methods operate reliably across both configuration regimes and achieve improved angle estimation performance with low overhead.