Flexible Antenna Arrays for Wireless Communications: Modeling and Performance Evaluation

TL;DR

The paper investigates flexible antenna arrays (rotatable, bendable, foldable) with a single flexible DoF $\psi$ to dynamically adjust antenna positions and orientations, shaping omni-directional and directional channels. It develops mathematical mappings for each FAA model, integrates them into a unified channel model, and analyzes multi-path power and angle CRB under directional patterns. Three FAA-based precoding schemes are proposed—Separate Flexible Precoding (SFP), Joint Flexible Precoding (JFP), and Semi-Joint Flexible Precoding (SJFP)—with Bayesian optimization-based ZF (BO-ZF) to optimize $\psi$ for maximum multi-sector sum-rate. Simulation results show substantial gains over fixed UPAs, notably up to $156\%$ in bendable JFP with directional patterns and notable improvements for rotatable FAAs in omni-pattern scenarios, underscoring the potential of shape-adaptive FAAs for coverage and interference management in 360-degree deployments.

Abstract

Flexible antenna arrays (FAAs), distinguished by their rotatable, bendable, and foldable properties, are extensively employed in flexible radio systems to achieve customized radiation patterns. This paper aims to illustrate that FAAs, capable of dynamically adjusting surface shapes, can enhance communication performances with both omni-directional and directional antenna patterns, in terms of multi-path channel power and channel angle Cramér-Rao bounds. To this end, we develop a mathematical model that elucidates the impacts of the variations in antenna positions and orientations as the array transitions from a flat to a rotated, bent, and folded state, all contingent on the flexible degree-of-freedom. Moreover, since the array shape adjustment operates across the entire beamspace, especially with directional patterns, we discuss the sum-rate in the multi-sector base station that covers the $360^\circ$ communication area. Particularly, to thoroughly explore the multi-sector sum-rate, we propose separate flexible precoding (SFP), joint flexible precoding (JFP), and semi-joint flexible precoding (SJFP), respectively. In our numerical analysis comparing the optimized FAA to the fixed uniform planar array, we find that the bendable FAA achieves a remarkable $156\%$ sum-rate improvement compared to the fixed planar array in the case of JFP with the directional pattern. Furthermore, the rotatable FAA exhibits notably superior performance in SFP and SJFP cases with omni-directional patterns, with respective $35\%$ and $281\%$.

Figures (8)

• Figure 1: Multi-sector communication system and three FAA types.
• Figure 2: Antenna position mapping and orientation mapping of three FAA models.
• Figure 3: Channel power gain of the three FAAs over the fixed array.
• Figure 4: Angle CRB versus the number of paths $L$ for three FAA and fixed UPA models under omni-directional and directional cosine pattern with $\kappa=1$.
• Figure 5: The predictive trend of three BO iterations with four inital measurement points.