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Passive Six-Dimensional Movable Antenna (6DMA)-Assisted Multiuser Communication

Haozhe Wang, Xiaodan Shao, Beixiong Zheng, Xiaoming Shi, Rui Zhang

TL;DR

This work tackles uplink multiuser capacity enhancement by deploying passive 6DMA surfaces (6D-IRS) whose 3D positions and rotations can be adjusted. It formulates a nonconvex joint optimization problem over surface placement, orientation, reflection coefficients, and BS beamforming to maximize the sum rate, and solves it via an alternating optimization framework combining MMSE beamforming, feasible-gradient-descent for geometry, and fractional programming for passive reflection. Key contributions include a comprehensive system model for cascaded 6D-IRS channels, a tractable AO algorithm, and numerical evidence that distributed passive surfaces outperform a single centralized surface and fixed IRS, particularly under directive radiation patterns. The findings suggest practical benefits of 6D-IRS in mitigating blockages and boosting uplink capacity in realistic wireless environments.

Abstract

Six-dimensional movable antenna (6DMA) is a promising solution for enhancing wireless network capacity through the adjustment of both three-dimensional (3D) positions and 3D rotations of distributed antenna surfaces. Previous works mainly consider 6DMA surfaces composed of active antenna elements, thus termed as active 6DMA. In this letter, we propose a new passive 6DMA system consisting of distributed passive intelligent reflecting surfaces (IRSs) that can be adjusted in terms of 3D position and 3D rotation. Specifically, we study a passive 6DMA-aided multiuser uplink system and aim to maximize the users' achievable sum rate by jointly optimizing the 3D positions, 3D rotations, and reflection coefficients of all passive 6DMA surfaces, as well as the receive beamforming matrix at the base station (BS). To solve this challenging non-convex optimization problem, we propose an alternating optimization (AO) algorithm that decomposes it into three subproblems and solves them alternately in an iterative manner. Numerical results are presented to investigate the performance of the proposed passive 6DMA system under different configurations and demonstrate its superior performance over the traditional fixed-IRS counterpart for both directive and isotropic radiation patterns of passive reflecting elements.

Passive Six-Dimensional Movable Antenna (6DMA)-Assisted Multiuser Communication

TL;DR

This work tackles uplink multiuser capacity enhancement by deploying passive 6DMA surfaces (6D-IRS) whose 3D positions and rotations can be adjusted. It formulates a nonconvex joint optimization problem over surface placement, orientation, reflection coefficients, and BS beamforming to maximize the sum rate, and solves it via an alternating optimization framework combining MMSE beamforming, feasible-gradient-descent for geometry, and fractional programming for passive reflection. Key contributions include a comprehensive system model for cascaded 6D-IRS channels, a tractable AO algorithm, and numerical evidence that distributed passive surfaces outperform a single centralized surface and fixed IRS, particularly under directive radiation patterns. The findings suggest practical benefits of 6D-IRS in mitigating blockages and boosting uplink capacity in realistic wireless environments.

Abstract

Six-dimensional movable antenna (6DMA) is a promising solution for enhancing wireless network capacity through the adjustment of both three-dimensional (3D) positions and 3D rotations of distributed antenna surfaces. Previous works mainly consider 6DMA surfaces composed of active antenna elements, thus termed as active 6DMA. In this letter, we propose a new passive 6DMA system consisting of distributed passive intelligent reflecting surfaces (IRSs) that can be adjusted in terms of 3D position and 3D rotation. Specifically, we study a passive 6DMA-aided multiuser uplink system and aim to maximize the users' achievable sum rate by jointly optimizing the 3D positions, 3D rotations, and reflection coefficients of all passive 6DMA surfaces, as well as the receive beamforming matrix at the base station (BS). To solve this challenging non-convex optimization problem, we propose an alternating optimization (AO) algorithm that decomposes it into three subproblems and solves them alternately in an iterative manner. Numerical results are presented to investigate the performance of the proposed passive 6DMA system under different configurations and demonstrate its superior performance over the traditional fixed-IRS counterpart for both directive and isotropic radiation patterns of passive reflecting elements.

Paper Structure

This paper contains 11 sections, 20 equations, 3 figures, 1 algorithm.

Table of Contents

  1. Introduction
  2. System Model and Problem Formulation
  3. Channel Model
  4. Signal Model
  5. Problem Formulation
  6. Proposed Solution
  7. Receive Beamforming Design
  8. Position and Rotation Optimization
  9. Passive Reflection Optimization
  10. Numerical Results
  11. Conclusion

Figures (3)

  • Figure 1: Passive 6DMA-assisted multiuser uplink communication.
  • Figure 2: Sum rate versus transmit power in the case of directive radiation pattern of REs.
  • Figure 3: Sum rate versus transmit power in the case of half-space isotropic radiation pattern of REs.