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Spider RIS: Mobilizing Intelligent Surfaces for Enhanced Wireless Communications

Ibrahim Yildirim, Mobeen Mahmood, Ertugrul Basar, Tho Le-Ngoc

TL;DR

This work introduces Spider RIS, a movable reconfigurable intelligent surface mounted on a ceiling platform that shifts its position to optimize wireless channels, addressing fixed-RIS and UAV energy limitations. It advances an angular-based hybrid beamforming design for mmWave mMIMO and a PSO-based method to jointly optimize RIS position and phase shifts, leveraging Saleh–Valenzuela channel modeling for TI and IR links. By deriving RF/BB beamformers and a dynamic RIS control scheme, the approach achieves notable rate gains over fixed RIS and relay systems while offering energy and cost advantages due to RIS passivity. The results underscore Spider RIS's potential to enhance indoor and outdoor wireless performance in dynamic environments, while highlighting the need for improved movement algorithms to overcome practical motion-related drawbacks.

Abstract

In this study, we introduce Spider RIS technology, which offers an innovative solution to the challenges encountered in movable antennas (MAs) and unmanned aerial vehicle (UAV)-enabled communication systems. By combining the dynamic adaptation capability of MAs and the flexible location advantages of UAVs, this technology offers a dynamic and movable RIS, which can flexibly optimize physical locations within the two-dimensional movement platform. Spider RIS aims to enhance the communication efficiency and reliability of wireless networks, particularly in obstructive environments, by elevating the signal quality and achievable rate. The motivation of Spider RIS is based on the ability to fully exploit the spatial variability of wireless channels and maximize channel capacity even with a limited number of reflecting elements by overcoming the limitations of traditional fixed RIS and energy-intensive UAV systems. Considering the geometry-based millimeter wave channel model, we present the design of a three-stage angular-based hybrid beamforming system empowered by Spider RIS: First, analog beamformers are designed using angular information, followed by the generation of digital precoder/combiner based on the effective channel observed from baseband stage. Subsequently, the joint dynamic positioning with phase shift design of the Spider RIS is optimized using particle swarm optimization, maximizing the achievable rate of the systems.

Spider RIS: Mobilizing Intelligent Surfaces for Enhanced Wireless Communications

TL;DR

This work introduces Spider RIS, a movable reconfigurable intelligent surface mounted on a ceiling platform that shifts its position to optimize wireless channels, addressing fixed-RIS and UAV energy limitations. It advances an angular-based hybrid beamforming design for mmWave mMIMO and a PSO-based method to jointly optimize RIS position and phase shifts, leveraging Saleh–Valenzuela channel modeling for TI and IR links. By deriving RF/BB beamformers and a dynamic RIS control scheme, the approach achieves notable rate gains over fixed RIS and relay systems while offering energy and cost advantages due to RIS passivity. The results underscore Spider RIS's potential to enhance indoor and outdoor wireless performance in dynamic environments, while highlighting the need for improved movement algorithms to overcome practical motion-related drawbacks.

Abstract

In this study, we introduce Spider RIS technology, which offers an innovative solution to the challenges encountered in movable antennas (MAs) and unmanned aerial vehicle (UAV)-enabled communication systems. By combining the dynamic adaptation capability of MAs and the flexible location advantages of UAVs, this technology offers a dynamic and movable RIS, which can flexibly optimize physical locations within the two-dimensional movement platform. Spider RIS aims to enhance the communication efficiency and reliability of wireless networks, particularly in obstructive environments, by elevating the signal quality and achievable rate. The motivation of Spider RIS is based on the ability to fully exploit the spatial variability of wireless channels and maximize channel capacity even with a limited number of reflecting elements by overcoming the limitations of traditional fixed RIS and energy-intensive UAV systems. Considering the geometry-based millimeter wave channel model, we present the design of a three-stage angular-based hybrid beamforming system empowered by Spider RIS: First, analog beamformers are designed using angular information, followed by the generation of digital precoder/combiner based on the effective channel observed from baseband stage. Subsequently, the joint dynamic positioning with phase shift design of the Spider RIS is optimized using particle swarm optimization, maximizing the achievable rate of the systems.
Paper Structure (10 sections, 17 equations, 5 figures, 1 table, 1 algorithm)

This paper contains 10 sections, 17 equations, 5 figures, 1 table, 1 algorithm.

Table of Contents

  1. Introduction
  2. System and Channel Model of Spider RIS
  3. System Model
  4. Channel Model
  5. Joint Hybrid Beamforming, RIS Dynamic Positioning and Phase Shift Design
  6. RF Beamforming/Combining Stage Design
  7. BB Precoder/Combiner Design
  8. Joint Dynamic RIS Positioning & Phase Shift Design
  9. Numerical Results
  10. Conclusions

Figures (5)

  • Figure 1: Illustration of a moving Spider RIS hanging on the ceiling platform in an indoor office environment according to changing positions.
  • Figure 2: Movable RIS-assisted mMIMO HBF system model.
  • Figure 3: Achievable rate comparison of movable RIS and relay-aided AB-HPC systems under increasing $P_T$.
  • Figure 4: Achievable rate comparison of different phase adjustment methods in RIS-aided AB-HPC systems for varying $M_I$.
  • Figure 5: Achievable rate comparison of different phase adjustment methods in RIS-aided AB-HPC systems for varying $M_I$.