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Ubiquitous Integrated Sensing and Communications for Massive MIMO LEO Satellite Systems

Li You, Yongxiang Zhu, Xiaoyu Qiang, Christos G. Tsinos, Wenjin Wang, Xiqi Gao, Björn Ottersten

TL;DR

This paper surveys the integration of sensing and communications (ISAC) within massive MIMO LEO satellite systems, arguing that 6G can achieve ubiquitous high-rate connectivity and sensing by leveraging LEO coverage and onboard large antenna arrays. It reviews LEO system characteristics, ISAC concepts, and how massive MIMO ISAC can be realized in space, then highlights two notable advances: multi-satellite-enabled ISAC with beam hopping and RIS-assisted IoT architectures. The authors identify key challenges—payload limitations, non-uniform traffic, Doppler and mobility effects, and beam squint—and propose enabling technologies such as software defined payloads/networks, hybrid beamforming, and edge intelligence. Open issues include novel antenna architectures (e.g., holographic metasurfaces, lens arrays), SAGSIN security, and advanced dual-functional waveforms (with OTFS as a candidate) to support robust space-based ISAC, offering a roadmap for practical 6G space–air–ground–sea integration.

Abstract

The next sixth generation (6G) networks are envisioned to integrate sensing and communications in a single system, thus greatly improving spectrum utilization and reducing hardware costs. Low earth orbit (LEO) satellite communications combined with massive multiple-input multiple-output (MIMO) technology holds significant promise in offering ubiquitous and seamless connectivity with high data rates. Existing integrated sensing and communications (ISAC) studies mainly focus on terrestrial systems, while operating ISAC in massive MIMO LEO satellite systems is promising to provide high-capacity communication and flexible sensing ubiquitously. In this paper, we first give an overview of LEO satellite systems and ISAC and consider adopting ISAC in the massive MIMO LEO satellite systems. Then, the recent research advances are presented. A discussion on related challenges and key enabling technologies follows. Finally, we point out some open issues and promising research directions.

Ubiquitous Integrated Sensing and Communications for Massive MIMO LEO Satellite Systems

TL;DR

This paper surveys the integration of sensing and communications (ISAC) within massive MIMO LEO satellite systems, arguing that 6G can achieve ubiquitous high-rate connectivity and sensing by leveraging LEO coverage and onboard large antenna arrays. It reviews LEO system characteristics, ISAC concepts, and how massive MIMO ISAC can be realized in space, then highlights two notable advances: multi-satellite-enabled ISAC with beam hopping and RIS-assisted IoT architectures. The authors identify key challenges—payload limitations, non-uniform traffic, Doppler and mobility effects, and beam squint—and propose enabling technologies such as software defined payloads/networks, hybrid beamforming, and edge intelligence. Open issues include novel antenna architectures (e.g., holographic metasurfaces, lens arrays), SAGSIN security, and advanced dual-functional waveforms (with OTFS as a candidate) to support robust space-based ISAC, offering a roadmap for practical 6G space–air–ground–sea integration.

Abstract

The next sixth generation (6G) networks are envisioned to integrate sensing and communications in a single system, thus greatly improving spectrum utilization and reducing hardware costs. Low earth orbit (LEO) satellite communications combined with massive multiple-input multiple-output (MIMO) technology holds significant promise in offering ubiquitous and seamless connectivity with high data rates. Existing integrated sensing and communications (ISAC) studies mainly focus on terrestrial systems, while operating ISAC in massive MIMO LEO satellite systems is promising to provide high-capacity communication and flexible sensing ubiquitously. In this paper, we first give an overview of LEO satellite systems and ISAC and consider adopting ISAC in the massive MIMO LEO satellite systems. Then, the recent research advances are presented. A discussion on related challenges and key enabling technologies follows. Finally, we point out some open issues and promising research directions.
Paper Structure (16 sections, 4 figures)

This paper contains 16 sections, 4 figures.

Table of Contents

  1. Introduction
  2. Overview of LEO Satellite Communication Systems, ISAC, and Massive MIMO LEO Satellite ISAC Systems
  3. LEO Satellite Communication Systems
  4. Overview of ISAC
  5. Massive MIMO LEO Satellite ISAC Systems
  6. Recent Research Advances
  7. Multi-Satellite-Enabled ISAC
  8. RIS-Assisted Satellites for IoT Networks
  9. Challenges and Key Technologies
  10. Challenges
  11. Key Technologies
  12. Open Issues and Research Opportunities
  13. Novel Antenna Architecture Design
  14. Space-Air-Ground-Sea Integrated Network (SAGSIN) Security With ISAC
  15. Novel Waveform Design
  16. ...and 1 more sections

Figures (4)

  • Figure 1: Illustration of a massive MIMO LEO satellite ISAC system setup.
  • Figure 2: (a) Communication beam coverage. (b) Localization beam coverage for Sat-1. (c) Localization beam coverage for Sat-2.
  • Figure 3: (a) RIS units scatter the incident wave. (b) RIS units beamform the incident wave. (c) RIS units provide LoS links.
  • Figure 4: (a) Energy efficiency performance versus power budget $P$ with 256 antennas under different weighting coefficient $\xi$. (b) Beampattern versus space angles with $\xi$ = 0.6. The red pentagrams locate the position of the targets.