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RIS-Empowered LEO Satellite Networks for 6G: Promising Usage Scenarios and Future Directions

Mesut Toka, Byungju Lee, Jaehyup Seong, Aryan Kaushik, Juhwan Lee, Jungwoo Lee, Namyoon Lee, Wonjae Shin, H. Vincent Poor

TL;DR

This work surveys RIS-empowered LEO satellite networks as a pathway to 6G, arguing that RISs can address LEO-specific challenges such as Doppler shifts, limited power, and blockage by enabling low-cost, energy-efficient, full-duplex propagation control. It surveys RIS basics, RIS-assisted use cases (including seamless access, Doppler compensation, link-quality enhancement, interference management, ISTN, and ISAC), and presents a practical discussion of AI-enabled RIS, THz HMIMO, and the remaining challenges in channel estimation, phase uncertainty, EMI, mobility, and multi-layer architecture. The authors discuss concrete system designs, including distributed RIS optimization and STAR-RIS configurations, and provide qualitative performance insights supported by example scenarios and figures. The paper concludes with a roadmap of future directions and challenges necessary to realize robust, scalable RIS-empowered NTN deployments for the 6G era, emphasizing integrated sensing, communication, and AI-driven control.”

Abstract

Low-Earth orbit (LEO) satellite systems have been deemed a promising key enabler for current 5G and the forthcoming 6G wireless networks. Such LEO satellite constellations can provide worldwide three-dimensional coverage, high data rate, and scalability, thus enabling truly ubiquitous connectivity. On the other hand, another promising technology, reconfigurable intelligent surfaces (RISs), has emerged with favorable features, such as flexible deployment, cost & power efficiency, less transmission delay, noise-free nature, and in-band full-duplex structure. LEO satellite networks have many practical imperfections and limitations; however, exploiting RISs has been shown to be a potential solution to overcome these challenges. Particularly, RISs can enhance link quality, reduce the Doppler shift effect, and mitigate inter-/intra beam interference. In this article, we delve into exploiting RISs in LEO satellite networks. First, we present a holistic overview of LEO satellite communication and RIS technology, highlighting potential benefits and challenges. Second, we describe promising usage scenarios and applications in detail. Finally, we discuss potential future directions and challenges on RIS-empowered LEO networks, offering futuristic visions of the upcoming 6G era.

RIS-Empowered LEO Satellite Networks for 6G: Promising Usage Scenarios and Future Directions

TL;DR

This work surveys RIS-empowered LEO satellite networks as a pathway to 6G, arguing that RISs can address LEO-specific challenges such as Doppler shifts, limited power, and blockage by enabling low-cost, energy-efficient, full-duplex propagation control. It surveys RIS basics, RIS-assisted use cases (including seamless access, Doppler compensation, link-quality enhancement, interference management, ISTN, and ISAC), and presents a practical discussion of AI-enabled RIS, THz HMIMO, and the remaining challenges in channel estimation, phase uncertainty, EMI, mobility, and multi-layer architecture. The authors discuss concrete system designs, including distributed RIS optimization and STAR-RIS configurations, and provide qualitative performance insights supported by example scenarios and figures. The paper concludes with a roadmap of future directions and challenges necessary to realize robust, scalable RIS-empowered NTN deployments for the 6G era, emphasizing integrated sensing, communication, and AI-driven control.”

Abstract

Low-Earth orbit (LEO) satellite systems have been deemed a promising key enabler for current 5G and the forthcoming 6G wireless networks. Such LEO satellite constellations can provide worldwide three-dimensional coverage, high data rate, and scalability, thus enabling truly ubiquitous connectivity. On the other hand, another promising technology, reconfigurable intelligent surfaces (RISs), has emerged with favorable features, such as flexible deployment, cost & power efficiency, less transmission delay, noise-free nature, and in-band full-duplex structure. LEO satellite networks have many practical imperfections and limitations; however, exploiting RISs has been shown to be a potential solution to overcome these challenges. Particularly, RISs can enhance link quality, reduce the Doppler shift effect, and mitigate inter-/intra beam interference. In this article, we delve into exploiting RISs in LEO satellite networks. First, we present a holistic overview of LEO satellite communication and RIS technology, highlighting potential benefits and challenges. Second, we describe promising usage scenarios and applications in detail. Finally, we discuss potential future directions and challenges on RIS-empowered LEO networks, offering futuristic visions of the upcoming 6G era.
Paper Structure (35 sections, 5 figures)

This paper contains 35 sections, 5 figures.

Table of Contents

  1. Introduction
  2. LEO Satellite Communication for 6G
  3. Main Advantages of LEO Systems
  4. Low-Latency and Link Quality Compared to GEO
  5. Global Coverage using LEO Constellations
  6. Frequency Reuse
  7. Key Challenges Facing 6G LEO Satellite Networks
  8. Doppler Effect
  9. Weak Line-of-Sight (LOS) Signal
  10. Power Limit
  11. Interference
  12. Motivations for Integrating RIS with LEO Satellite Networks
  13. Basic Concepts of RIS
  14. Potential Benefits
  15. Cost Effective and Power Efficient
  16. ...and 20 more sections

Figures (5)

  • Figure 1: Comparison of passive RIS, active RIS, and STAR-RIS.
  • Figure 2: RIS-empowered scenarios in LEO satellite networks. SU: satellite user, and CU: cellular user.
  • Figure 3: RIS-assisted channel reconfiguration: (a) System model and elevation angle versus LOS probability and (b) Received SNR (dB) versus the number of RIS elements.
  • Figure 4: OP performance of RIS-aided LEO network under frequent heavy shadowing environment.
  • Figure 5: AI-enabled RIS-aided LEO satellites with ISAC functionalities for public safety operations.