Enhancing LEO Mega-Constellations with Inter-Satellite Links: Vision and Challenges

TL;DR

This paper addresses the bottleneck of ground-station connectivity in LEO mega-constellations by examining inter-satellite links (ISLs) as a path to autonomous, high-capacity space networks. It surveys ISL visions, classifies ISL-empowered and ISL-inspired applications, and analyzes core design challenges in performance, routing, and resource allocation, supported by a case study on in-flight connectivity. Key contributions include theoretical insights into ISL path selection, gateway placement, and constellation design, plus considerations for dynamic routing, load balancing, and joint optimization of ISL scheduling and data offloading. The work highlights open issues such as SAGIN integration, RIS-enabled ISLs, LISL-specific challenges, and the role of AI in network control, underscoring the practical impact of ISLs for 6G-era global connectivity and resilience.

Abstract

Low Earth orbit (LEO) satellites have been envisioned as a significant component of the sixth generation (6G) network architecture for achieving ubiquitous coverage and seamless access. However, the implementation of LEO satellites is largely restricted by the deployment of ground stations. Inter-satellite links (ISLs) have been regarded as a promising technique to fully exploit the potentials of LEO mega constellations by concatenating multiple satellites to constitute an autonomous space network. In this article, we present the merits of implementing ISLs in LEO mega constellations and the representative applications empowered/inspired by ISLs. Moreover, we outline several key technical challenges as well as potential solutions related to LEO satellite networks with ISLs, including performance analysis for system design, routing and load balancing, and resource allocation. Particularly, the potential of using ISLs in enhancing in-flight connectivity is showcased with a preliminary performance evaluation. Finally, some open issues are discussed to inspire future research.

Figures (4)

• Figure 1: Typical application scenarios for ISLs.
• Figure 2: Illustration of a routing scenario in LEO mega constellations
• Figure 3: Proposed framework to realize IFC by exploiting ISLs.
• Figure 4: Average delay versus the maximum number of realizable ISLs.