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LEO Satellite Constellations for 5G and Beyond: How Will They Reshape Vertical Domains?
Shicong Liu, Zhen Gao, Yongpeng Wu, Derrick Wing Kwan Ng, Xiqi Gao, Kai-Kit Wong, Symeon Chatzinotas, Bjorn Ottersten
TL;DR
Terrestrial cellular networks leave high-bandwidth coverage concentrated in urban areas, motivating LEO satellite integration to connect underserved regions. The paper surveys LEO constellation development, evaluates integration opportunities through KPIs and enabling technologies, and discusses vertical domains that may be reshaped by the resulting capabilities.
Problem
Terrestrial cellular networks concentrate high-bandwidth coverage in urban areas, leaving a geographical digital divide that motivates connecting underserved regions.
Method
The paper presents a development roadmap for LEO SatCons and examines their integration with future cellular networks through space-based wireless KPIs and enabling technologies.
Results
LEO SatCons offer integration-relevant advantages including around 3 ms round-trip air-interface latency, improved reliability through spatial diversity, and higher availability as constellation size increases.
Takeaways & Limitations
The paper concludes that superior LEO SatCon KPIs can support diverse service requirements and help reshape vertical applications and domains.
Abstract
from arXiv · showhide
The rapid development of communication technologies in the past decades has provided immense vertical opportunities for individuals and enterprises. However, conventional terrestrial cellular networks have unfortunately neglected the huge geographical digital divide, since high bandwidth wireless coverage is concentrated to urban areas. To meet the goal of ``connecting the unconnected'', integrating low Earth orbit (LEO) satellites with the terrestrial cellular networks has been widely considered as a promising solution. In this article, we first introduce the development roadmap of LEO satellite constellations (SatCons), including early attempts in LEO satellites with the emerging LEO constellations. Further, we discuss the unique opportunities of employing LEO SatCons for the delivery of integrating 5G networks. Specifically, we present their key performance indicators, which offer important guidelines for the design of associated enabling techniques, and then discuss the potential impact of integrating LEO SatCons with typical 5G use cases, where we engrave our vision of various vertical domains reshaped by LEO SatCons. Technical challenges are finally provided to specify future research directions.
I. INTRODUCTION
5G and beyond-5G networks seek ubiquitous connectivity for diverse vertical industries, but terrestrial coverage remains concentrated in urban areas. LEO satellite constellations are presented as a way to extend connectivity, reduce latency, and support flexible global deployment.
- 5G targets ubiquitous connections and supports eMBB, mMTC, and URLLC vertical scenarios.
- Nearly half of the population remains unconnected, while terrestrial expansion burdens operators and leaves aero and maritime coverage unresolved.
- LEO, MEO, and GEO satellites can collaborate as SatCons, changing terrestrial networks’ static topology and enabling flexible deployment.
- LEO’s lower altitude reduces latency for delay-sensitive tasks, while dense constellations provide global service capacity.
- The article reviews LEO SatCon development, integration opportunities, technical challenges, and research directions.
A. Overview of Early LEO Satellites
Early LEO constellation efforts established important technical precedents but largely failed commercially, while emerging megaconstellations target global broadband connectivity and renewed integration with terrestrial networks.
- Early LEO constellation attempts generally ended in bankruptcy, although their experiences provided lessons for later ventures.
- Globalstar used a Walker Delta pattern with 48 satellites at 1414 km, offering mid-latitude diversity but no polar coverage.
- Teledesic initially proposed 840 satellites at 700 km for broadband access before scaling down to no more than 288.
- Early trials lost business against terrestrial networks because vertical markets were insufficiently developed to support mature LEO commercial operations.
- Starlink plans around 42000 satellites, while OneWeb, Telesat, and Project Kuiper pursue global coverage or broadband access for uncovered users.
III. OPPORTUNITIES OF LEO SATCONS FOR 5G AND BEYOND
The paper examines how LEO SatCons can complement terrestrial 5G and beyond-5G systems by evaluating space-network KPIs. Lower altitude reduces latency, while constellation scale improves reliability and availability.
- The paper evaluates LEO SatCons’ KPIs to identify advantages over terrestrial 5G and motivate integration with B5G systems.
- 1) Latency: Around 3 ms round-trip air-interface latency at 320 km meets control-plane requirements for most eMBB and mMTC usage.
- 2) Reliability: Larger constellations improve reliability by allowing users to be served by more satellites simultaneously, yielding spatial-diversity gains.
3) Data rate:
Data rate, cost, mobility, and connection density shape the practical deployment of LEO SatCons for vertical applications. The paper identifies terrestrial limitations and satellite-specific operational challenges that must be addressed.
- 3) Data rate: Customized streaming rates remain limited relative to approximately 30 Mbps digital video broadcasting, motivating renewed attention to data rate in SatCon design.
- 5) Cost: Cost constrains profitability and long-term viability because manufacturing, launching, and operating satellites impose substantial financial burdens.
- 6) Mobility: Satellite mobility management must handle moving user terminals and high-speed satellites, including paging, handover, and changing Doppler shifts.
- Low-cost satellite receivers can support massive machine-type connectivity where terrestrial base stations are insufficient, especially in rural and pathless areas.
8) Survivability:
LEO SatCons are presented as a way to address terrestrial connectivity and deployment constraints across several vertical domains. Their flexible wireless topology supports disaster recovery, while their connectivity and positioning capabilities are linked to industrial and agricultural applications.
- LEO SatCons can withstand natural disasters better than fragile terrestrial optical cables because their flexible topology and wireless access support disaster recovery.
- Industrial IoT: Industrial IoT requires fine-grained connectivity and high-accuracy positioning, traditionally requiring massive terrestrial base-station deployment.
- Industrial IoT: LEO SatCons are presented as a viable approach for addressing Industrial IoT connectivity and positioning challenges and enabling business-to-business promotion.
- Agriculture: Agriculture faces costly optical-cable deployment because cultivated land is typically vast and sparsely populated.
- Agriculture: Deploying LEO satellites for crop and livestock monitoring and unmanned operations is described as an inevitable trend that could significantly contribute to agricultural productivity.
3) eHealth:
LEO SatCons are associated with broad opportunities for eHealth, energy, transportation, remote interaction, and finance. The supplied passages emphasize global or remote coverage, low latency, and real-time monitoring or control as recurring enablers.
- eHealth: LEO SatCons could support ubiquitous eHealth access, decentralized medical services, and real-time monitoring and analysis of health data from wearable devices.
- Energy: LEO SatCons are presented as suitable for intelligent and remote energy operations in fossil-energy sites located far from terrestrial 5G coverage.
- Intelligent Vehicular Networks: LEO SatCons can provide wide coverage and improved reliability, capacity, and latency for airplanes, vessels, and high-speed trains as dynamic network nodes.
- Remote Interactions: Global LEO coverage with low latency and wide bandwidth could enable remote education, work, entertainment, and shopping for rural and isolated populations.
- Finance: LEO satellites could improve asset-tracking reliability and GPS positioning accuracy, while their lower-latency space transmissions may benefit high-frequency trading.
8) Smart City:
Smart-city systems can connect massive IoT sensing to a City Brain, while LEO satellites support real-time coordination and dynamic resource allocation for urban services.
- Smart cities connect massive IoT sensors distributed across cities directly to the City Brain for real-time cross-system data processing.
- LEO satellites support synchronous information exchange and dynamic resource allocation with fast response and high concurrency.
- These capabilities are envisioned for traffic management, large-scale activity-flow monitoring, smart tourism, and cloud-edge infrastructure management.
- Integrating spaceborne, airborne, and terrestrial networks can enhance SatCons’ service coverage and QoS for diverse vertical scenarios.
B. Mobility Management
LEO mobility management must maintain service as rapidly moving spotbeams change coverage, requiring adapted paging and handover procedures across link-layer connectivity changes.
- LEO spotbeams move rapidly along fixed trajectories, so cells are covered by different satellite beams over time.
- Paging and handover procedures must account for the relative motion between the cell pattern and the tracking area.
- Link-layer handover occurs when high-mobility connectivity changes alter one or more links between communication nodes.
- Spotbeam handover transfers service when terrestrial nodes cross adjacent spotbeam boundaries on one satellite.
- Satellite handover transfers a node from a previous satellite when that satellite no longer provides service.
- ISL handover follows an interrupted inter-satellite link caused by changing distance or field-of-view angle and introduces rerouting issues.
2) Network layer:
Network-layer integration must address changing satellite IP bindings and unresolved incompatibilities between current 5G technology and non-terrestrial networks.
- Network-layer handover occurs when a satellite or terrestrial node changes its IP address.
- A satellite’s IP address must be updated when it leaves one terrestrial station’s coverage and bonds with another.
- Accurate user-terminal locations and LEO ephemeris can help select beams and estimate coverage duration for handover and paging.
- Commercial mobile-satellite solutions currently include terrestrial gateways, tailored antennas, and specified user terminals.
- Current 5G and non-terrestrial-network integration still contains incompatibilities requiring resolution.
- Spectrum scarcity is expected to intensify as 5G bands become crowded and tens of thousands of satellites increase demand, motivating higher-frequency Ka-band use.
2) Advanced array and multi-beam technique:
Advanced arrays, multibeam links, and inter-satellite technologies are proposed to support flexible beamforming and high traffic, while satellite channels create demanding synchronization and access challenges.
- Massive MIMO with phased arrays is expected to support flexible beamforming on SatCons as availability, data-rate, and reliability demands increase.
- Active phased arrays and multibeam antennas on user terminals require further research for satellite-network integration.
- THz and FSO are promising ISL techniques because of high directivity, ultra-wide bandwidth, and security characteristics.
- Satellite wireless channels are generally Rician line-of-sight channels, while high-speed motion makes Doppler mitigation and synchronization challenging.
- Propagation latency makes low-latency processing especially challenging for massive IoT access networks.
- Grant-free random access reduces latency by allowing pilots and data transmission without permission, but increases spectrum consumption with more users and requires accurate channel state information.
- The article positions key techniques as pillars for achieving superior KPIs and supporting diverse service requirements across vertical applications.
Inter-satellite link
The section references visual material on LEO SatCon architecture, access modes, vertical-domain impacts, handover schemes, and relationships among domains, requirements, and techniques.
- Fig. 6 presents an ambitious vision of vertical domains reshaped by LEO SatCons.
- Fig. 7 illustrates typical link layer handover schemes.
- Fig. 8 relates vertical domains to service requirements and key techniques.