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Joint Beamforming and Position Optimization for Movable-Antenna and Movable-Element RIS-Aided Full-Duplex 6G MISO Systems

Ayda Nodel Hokmabadi, Chadi Assi

TL;DR

This work addresses the challenge of enabling high-performance full-duplex operation in 6G MISO networks by introducing a joint movable-antenna base station (MA-BS) and movable-element RIS (ME-RIS) architecture. An alternating-optimization framework is developed to maximize the sum-rate, coupling BS downlink beamforming, uplink reception, RIS phase shifts, and 3D positions of all movable components through SDR-SROCR and SCA-based position updates. The approach yields substantial gains over conventional fixed-geometry designs, with performance improving as the number of RIS elements grows and under effective self-interference suppression. The results highlight movable antennas and movable RIS elements as a powerful combination for shaping channels and mitigating interference, enabling practical high-throughput FD operation in future 6G networks.

Abstract

Full-duplex communication substantially enhances spectral efficiency by enabling simultaneous transmission and reception on the same time-frequency resources. However, its practical deployment remains hindered by strong residual self-interference and inter-user interference, which severely degrade system performance. This work investigates a full-duplex MISO network that leverages movable-antenna base stations (MA-BS) and movable-element reconfigurable intelligent surfaces (ME-RIS) to overcome these limitations in next-generation 6G systems. Unlike conventional fixed-geometry architectures, the proposed framework jointly optimizes antenna and RIS element positions, together with RIS phase shifts, to strengthen desired links while suppressing interference. Our design objective is to maximize the system sum rate through the joint optimization of transmit and receive beamforming vectors, uplink transmit powers, RIS phase shifts, and the spatial locations of both the BS antennas and RIS elements. To solve this challenging nonconvex problem, an alternating optimization algorithm is developed, employing semidefinite relaxation for beamforming design and successive convex approximation for position optimization. Simulation results demonstrate that the proposed ME-RIS-assisted architecture with movable BS antennas offers substantial gains over conventional fixed-position full-duplex networks. These findings highlight the potential of integrating movable antennas with movable RIS elements as a key enabler for high-performance full-duplex operation in future 6G wireless systems.

Joint Beamforming and Position Optimization for Movable-Antenna and Movable-Element RIS-Aided Full-Duplex 6G MISO Systems

TL;DR

This work addresses the challenge of enabling high-performance full-duplex operation in 6G MISO networks by introducing a joint movable-antenna base station (MA-BS) and movable-element RIS (ME-RIS) architecture. An alternating-optimization framework is developed to maximize the sum-rate, coupling BS downlink beamforming, uplink reception, RIS phase shifts, and 3D positions of all movable components through SDR-SROCR and SCA-based position updates. The approach yields substantial gains over conventional fixed-geometry designs, with performance improving as the number of RIS elements grows and under effective self-interference suppression. The results highlight movable antennas and movable RIS elements as a powerful combination for shaping channels and mitigating interference, enabling practical high-throughput FD operation in future 6G networks.

Abstract

Full-duplex communication substantially enhances spectral efficiency by enabling simultaneous transmission and reception on the same time-frequency resources. However, its practical deployment remains hindered by strong residual self-interference and inter-user interference, which severely degrade system performance. This work investigates a full-duplex MISO network that leverages movable-antenna base stations (MA-BS) and movable-element reconfigurable intelligent surfaces (ME-RIS) to overcome these limitations in next-generation 6G systems. Unlike conventional fixed-geometry architectures, the proposed framework jointly optimizes antenna and RIS element positions, together with RIS phase shifts, to strengthen desired links while suppressing interference. Our design objective is to maximize the system sum rate through the joint optimization of transmit and receive beamforming vectors, uplink transmit powers, RIS phase shifts, and the spatial locations of both the BS antennas and RIS elements. To solve this challenging nonconvex problem, an alternating optimization algorithm is developed, employing semidefinite relaxation for beamforming design and successive convex approximation for position optimization. Simulation results demonstrate that the proposed ME-RIS-assisted architecture with movable BS antennas offers substantial gains over conventional fixed-position full-duplex networks. These findings highlight the potential of integrating movable antennas with movable RIS elements as a key enabler for high-performance full-duplex operation in future 6G wireless systems.
Paper Structure (30 sections, 53 equations, 7 figures, 1 table, 2 algorithms)

This paper contains 30 sections, 53 equations, 7 figures, 1 table, 2 algorithms.

Table of Contents

  1. Introduction
  2. Contributions
  3. Organization
  4. System Model
  5. Network Model
  6. Signal Model
  7. Downlink Transmission
  8. Uplink Transmission
  9. Sum-rate
  10. Field-Response Based Channel Model
  11. Downlink channels
  12. Uplink channels
  13. Problem Formulation
  14. Proposed AO-based Algorithms
  15. Downlink beamforming vector at BS ($\boldsymbol{\omega}$)
  16. ...and 15 more sections

Figures (7)

  • Figure 1: Full-duplex system model
  • Figure 2: Sum rate versus the number of RIS elements $N$.
  • Figure 3: Sum rate versus residual self-interference level $\eta$.
  • Figure 4: Sum rate versus the maximum transmit power at the BS, $P^{\text{BS}}_{\max}$.
  • Figure 5: Sum rate for the full--duplex and the half--duplex networks.
  • ...and 2 more figures