Movable-Antenna Enhanced Multiuser Communication via Antenna Position Optimization

TL;DR

Simulation results demonstrate that the proposed solutions for MA-enhanced multiple access systems can significantly decrease the total transmit power of users as compared to conventional FPA systems employing antenna selection under both perfect and imperfect field-response information.

Abstract

Movable antenna (MA) is a promising technology to improve wireless communication performance by varying the antenna position in a given finite area at the transceivers to create more favorable channel conditions. In this paper, we investigate the MA-enhanced multiple-access channel (MAC) for the uplink transmission from multiple users each equipped with a single MA to a base station (BS) with a fixed-position antenna (FPA) array. A field-response based channel model is used to characterize the multi-path channel between the antenna array of the BS and each user's MA with a flexible position. To evaluate the MAC performance gain provided by MAs, we formulate an optimization problem for minimizing the total transmit power of users, subject to a minimum-achievable-rate requirement for each user, where the positions of MAs and the transmit powers of users, as well as the receive combining matrix of the BS are jointly optimized. To solve this non-convex optimization problem involving intricately coupled variables, we develop two algorithms based on zero-forcing (ZF) and minimum mean square error (MMSE) combining methods, respectively. Specifically, for each algorithm, the combining matrix of the BS and the total transmit power of users are expressed as a function of the MAs' position vectors, which are then optimized by using the proposed multi-directional descent (MDD) framework. It is shown that the proposed ZF-based and MMSE-based MDD algorithms can converge to high-quality suboptimal solutions with low computational complexities. Simulation results demonstrate that the proposed solutions for MA-enhanced multiple access systems can significantly decrease the total transmit power of users as compared to conventional FPA systems employing antenna selection under both perfect and imperfect field-response information.

Figures (13)

• Figure 1: Illustration of the uplink transmission between $K$ single-MA users and the BS equipped with a UPA of size $N=N_{1} \times N_{2}$.
• Figure 2: Illustration of the 3D local coordinate system and the corresponding spatial angles for user $k$, $1 \leq k \leq K$.
• Figure 3: Evaluation of the convergence of the proposed Algorithms \ref{['alg_ZF']} and \ref{['alg_MMSE']}.
• Figure 4: Average receive powers of the target signals and interference for multiple users normalized by noise power versus iteration index.
• Figure 5: Channel power gain (dB) between the antenna array of the BS and the MA of a single user.