Rotatable Antenna-Enhanced Cell-Free Communication

TL;DR

This paper explores the use of rotatable antennas in cell-free systems to enhance downlink communication, jointly optimizing access point associations and antenna directions to improve overall data rates.

Contribution

It introduces a novel RA-enhanced cell-free system and a two-stage optimization strategy for AP-user association and antenna direction control.

Findings

Significant increase in sum rate compared to benchmarks

Effective joint optimization of AP associations and antenna directions

Demonstrated advantages of RA technology in cell-free networks

Abstract

Rotatable antenna (RA) is a promising technology that can exploit new spatial degrees-of-freedom (DoFs) by flexibly adjusting the three-dimensional (3D) boresight direction of antennas. In this letter, we investigate an RA-enhanced cell-free system for downlink transmission, where multiple RA-equipped access points (APs) cooperatively serve multiple single-antenna users over the same time-frequency resource. Specifically, we aim to maximize the sum rate of all users by jointly optimizing the AP-user associations and the RA boresight directions. Accordingly, we propose a two-stage strategy to solve the AP-user association problem, and then employ fractional programming (FP) and successive convex approximation (SCA) techniques to optimize the RA boresight directions. Numerical results demonstrate that the proposed RA-enhanced cell-free system significantly outperforms various benchmark schemes.