Robust Movable-Antenna Position Optimization with Imperfect CSI for MISO Systems

TL;DR

This paper develops a robust optimization framework for movable antenna positioning in MISO systems under imperfect CSI, deriving closed-form solutions and demonstrating improved performance over benchmarks.

Contribution

It introduces a novel robust position optimization method considering two types of CSI errors, with closed-form solutions and a graph-based algorithm for MISO systems.

Findings

Optimality of maximum-ratio transmission under imperfect CSI

Closed-form expressions for worst-case and non-outage received signal power

Proposed scheme outperforms benchmarks even with imperfect CSI

Abstract

Movable antenna (MA) technology has emerged as a promising solution for reconfiguring wireless channel conditions through local antenna movement within confined regions. Unlike previous works assuming perfect channel state information (CSI), this letter addresses the robust MA position optimization problem under imperfect CSI conditions for a multiple-input single-output (MISO) MA system. Specifically, we consider two types of CSI errors: norm-bounded and randomly distributed errors, aiming to maximize the worst-case and non-outage received signal power, respectively. For norm-bounded CSI errors, we derive the worst-case received signal power in closed-form. For randomly distributed CSI errors, due to the intractability of the probabilistic constraints, we apply the Bernstein-type inequality to obtain a closed-form lower bound for the non-outage received signal power. Based on these results, we show the optimality of the maximum-ratio transmission for imperfect CSI in both scenarios and employ a graph-based algorithm to obtain the optimal MA positions. Numerical results show that our proposed scheme can even outperform other benchmark schemes implemented under perfect CSI conditions.