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A Survey on Non-Geostationary Satellite Systems: The Communication Perspective

Hayder Al-Hraishawi, Houcine Chougrani, Steven Kisseleff, Eva Lagunas, Symeon Chatzinotas

arXiv:2107.05312v4eess.SP

TL;DR

Existing surveys leave room for an integrated account of NGSO communication technologies and system designs. This paper surveys research across communication layers and deployment challenges, concluding with research directions and opportunities for NGSO communications.

  • Problem

    Existing surveys do not provide the paper’s integrated coverage of NGSO communications from the physical layer through applications and structural designs.

    Source: C. Scope and Contributions · p. 3

  • Method

    The paper conducts a broad survey of NGSO communication technologies, networking, system designs, deployment challenges, and research directions.

    Source: §VI · p. 26

  • Results

    The survey synthesizes developments across NGSO communication layers and structural designs, and examines integration challenges and future research directions.

    Source: §VI · p. 26

  • Takeaways & Limitations

    NGSO integration research must address coexistence with GSO systems, constellation design, resource management, and user equipment requirements.

    Source: §VI · p. 26

    Interference between inter-satellite links requires further investigation, including under constellation dynamics.

    Source: 2) Interference Management · p. 18

Abstract

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The next phase of satellite technology is being characterized by a new evolution in non-geostationary orbit (NGSO) satellites, which conveys exciting new communication capabilities to provide non-terrestrial connectivity solutions and to support a wide range of digital technologies from various industries. NGSO communication systems are known for a number of key features such as lower propagation delay, smaller size, and lower signal losses in comparison to the conventional geostationary orbit (GSO) satellites, which can potentially enable latency-critical applications to be provided through satellites. NGSO promises a substantial boost in communication speed and energy efficiency, and thus, tackling the main inhibiting factors of commercializing GSO satellites for broader utilization. The promised improvements of NGSO systems have motivated this paper to provide a comprehensive survey of the state-of-the-art NGSO research focusing on the communication prospects, including physical layer and radio access technologies along with the networking aspects and the overall system features and architectures. Beyond this, there are still many NGSO deployment challenges to be addressed to ensure seamless integration not only with GSO systems but also with terrestrial networks. These unprecedented challenges are also discussed in this paper, including coexistence with GSO systems in terms of spectrum access and regulatory issues, satellite constellation and architecture designs, resource management problems, and user equipment requirements. Finally, we outline a set of innovative research directions and new opportunities for future NGSO research.

I. INTRODUCTION · A. Background · B. Prior Related Surveys

NGSO’s lower-orbit properties and emerging constellations motivate expanded connectivity, while this survey examines communication research, deployment challenges, and future directions in a field not comprehensively covered by prior surveys.

I. INTRODUCTION

  • Operators are planning thousands of NGSO satellites amid rising broadband demand, while satellite backhaul and 5G integration are gaining traction.NewSpace firms are developing small satellites with low-cost launchers.Source: §I · p. 1
  • NGSO satellites could support 6G non-terrestrial networks, extend 5G connectivity to underserved areas, and bridge the digital divide.Satellite services already reach aeronautical, maritime, military, rescue, and disaster-relief sectors; 3GPP is codifying space-airborne-terrestrial integration.Source: §I · p. 1

A. Background

  • Unlike GSO satellites, lower-altitude LEO, MEO, and HEO satellites offer lower propagation losses and latency, but require constellations for full-Earth coverage.GSO satellites cannot cover high-latitude areas and need large antennas and higher transmit power because of link losses.Source: A. Background · p. 1
  • NGSO deployment has accelerated, with more than 4,000 operational satellites in orbit and a recent wave of proposals for large LEO broadband constellations.The passage reports a larger number of NGSO than GSO satellites and cites achievements from SpaceX, SES O3B, and OneWeb.Source: A. Background · p. 2
  • Steerable beams, smaller user-terminal equipment, mobile-platform connectivity, and throughput-enhancement techniques support NGSO service capacity reaching terabits per second.Techniques include spectrum sharing, cooperative gateway diversity, user clustering, interference mitigation, and multiple-antenna communications.Source: A. Background · p. 2
  • The survey examines NGSO communication progress, deployment challenges, and future research opportunities, including how shorter-lived, cheaper satellites may enable more regular infrastructure upgrades.The authors note that more frequent upgrades could allow more innovative onboard payload designs.Source: A. Background · p. 2

B. Prior Related Surveys

  • Prior surveys address satellite-terrestrial convergence, inter-satellite communication, integrated networks, LMS limitations, small satellites, and broader satellite advances and security,.Their topics include architectures, protocols, frequency bands, optical communications, applications, and physical-layer security.Source: B. Prior Related Surveys · pp. 2–3
  • Other surveys cover LEO and CubeSat connectivity and networking –, 3GPP NTN integration,, and satellite-terrestrial convergence and hybrid networks,.The authors identify a gap: no comprehensive survey covers multi-orbit NGSO communications, integration challenges, regulatory coexistence, user-equipment requirements, and future opportunities together.Source: B. Prior Related Surveys · p. 3

C. Scope and Contributions · D. Structure and Organization

The paper surveys multi-orbit NGSO satellite communications from system classification and communication technologies through deployment challenges and future prospects. It also maps the paper’s organization across these topics.

C. Scope and Contributions

  • The survey covers multi-orbit NGSO trends and prospects, from space-based Internet providers and small satellites to communication layers, system design, deployment, and integration.It also summarizes NGSO features and use cases as a reference for researchers and practitioners.Source: C. Scope and Contributions · p. 3
  • The paper classifies NGSO systems by application, including broadband mega-constellations and satellites for space downstream missions.Source: C. Scope and Contributions · pp. 3–4
  • Its communication survey spans physical-layer technologies, radio access schemes, networking, and overall system characteristics and architectures.Source: C. Scope and Contributions · p. 4
  • The survey analyzes deployment and operational challenges, including GSO coexistence and regulation, constellation design, and user hardware capabilities and requirements.Source: C. Scope and Contributions · p. 4
  • It examines satellite evolution and integrated satellite-terrestrial systems, identifying research directions for versatile communication infrastructures and new application scenarios.The paper also considers potential technical advances in future communications and networking from NGSO involvement.Source: C. Scope and Contributions · p. 4

D. Structure and Organization

  • The paper proceeds from NGSO definitions and classification to communication prospects, deployment challenges, future research directions, and conclusions.Figure 2 shows the paper’s structure, and Table II lists frequently used acronyms and their definitions.Source: D. Structure and Organization · p. 4

II. NGSO SYSTEM CHARACTERISTICS AND CLASSIFICATION · A. Space-based Internet Providers

The paper distinguishes early NGSO systems for voice and low-rate data from newer broadband constellations, then describes space-based Internet providers, their architectures, and leading projects. These systems aim to extend high-speed, low-latency Internet access to underserved users and locations.

II. NGSO SYSTEM CHARACTERISTICS AND CLASSIFICATION

  • ITU distinguishes early NGSO systems designed for voice and low-rate data from newer constellations aimed at global broadband, with only O3b and Starlink operational among the latter to date.Iridium, Globalstar, and Orbcomm became operational in the late 1990s; early systems typically used MSS L- and S-band, while modern systems use Ku- and Ka-band for user links.Source: §II · pp. 4–5
  • NGSO constellations can offer high throughput and spectral efficiency, bypass terrestrial infrastructure through ISLs to improve privacy, reduce latency versus fiber, and cover higher latitudes than GSO satellites.The cited comparison gives light speed as 3 × 10^8 m/s in free space versus 2 × 10^8 m/s in fiber-optic cable.Source: §II · pp. 5–6
  • The paper classifies NGSO systems by service into space-based Internet providers and space missions, amid applications including telecommunications, observation, navigation, tracking, meteorology, and science.Source: §II · p. 6

A. Space-based Internet Providers

  • Space-based NGSO providers target high-speed, low-latency Internet for backhaul, mobile users, underserved populations, high-latitude regions, and maritime and aeronautical services.The passage reports that only 39% of the world's population has access to terrestrial broadband infrastructure; satellite service can reach places where fiber is financially unfeasible.Source: A. Space-based Internet Providers · p. 6
  • A space-based Internet system comprises space, ground, and user segments, coordinated by an NMC for system management and an NCC for real-time control signalling.The ground segment's gateways relay Internet data, while the user segment commonly uses a VSAT antenna and transceiver.Source: A. Space-based Internet Providers · pp. 6–7
  • Starlink's planned initial constellation approaches 12,000 satellites, using phased-array antennas and regenerative payloads to steer beams individually toward users.A possible later extension is to 42,000 satellites, and envisioned per-satellite throughput is 17–23 Gbps depending on user-terminal characteristics.Source: A. Space-based Internet Providers · p. 7
  • OneWeb's initial plan calls for 648 satellites in 18 polar-orbit planes at 1,200 km, with transparent bent-pipe payloads and non-steerable user beams.The passage says 110 satellites had already launched and describes two steerable gateway antennas per satellite, one active and one for handover backup.Source: A. Space-based Internet Providers · p. 7
  • O3b's 20 equatorial MEO satellites provide broadband around 500 Mbit/sec, while O3b mPOWER plans 11 MEO satellites with steerable, real-time-scalable spot beams for global broadband.Other announced ventures include Amazon's Project Kuiper, LeoSat, Telesat LEO, Boeing, and Huawei's Massive VLEO constellation.Source: A. Space-based Internet Providers · pp. 7–8

B. NGSO Space Missions · 1) Earth and Space Observation: · 2) Asset Tracking:

The paper surveys NGSO missions enabled by more affordable and accessible satellite technology, including Earth and space observation and asset tracking.

B. NGSO Space Missions

  • Smaller, more affordable satellites have broadened access to space and enabled missions for diverse needs and applications.The paper notes that countries, universities, startups, and schools can now reach space affordably and within short periods.Source: B. NGSO Space Missions · p. 8

1) Earth and Space Observation:

  • Small-satellite constellations support high-resolution Earth and space imaging, including mapping, exoplanet searches, and telescope guide-star proposals.Examples include NASA’s TESS mission, launched in 2018 to search for planets outside the solar system, and proposals to use small satellites as guide stars.Source: 1) Earth and Space Observation · p. 8

2) Asset Tracking:

  • NGSO asset-tracking payloads collect information from ground objects and relay it to stations, providing stable, precise service with global coverage.The section identifies this as a main NGSO field and describes the payload as a device equipped with communication components.Source: 2) Asset Tracking · p. 8
  • NGSO tracking supports fleet management of vehicles and industrial machinery, while lower-orbit constellations can aid precise control in inaccessible areas.The passage also says these constellations can strengthen wireless networks and support control of mobile resources.Source: 2) Asset Tracking · p. 8
  • Satellite constellations let logistics companies track goods in real time, estimate arrival times, and improve security, control, and traceability.Tracking can cover containers, goods, and machinery requiring controlled transport conditions such as temperature or movement across road, rail, air, and sea routes.Source: 2) Asset Tracking · p. 8
  • NGSO small satellites can improve vessel safety and location monitoring, particularly where terrestrial-network coverage is limited.They can also help control problems affecting maritime traffic and maintain vessel location and control in low-coverage areas.Source: 2) Asset Tracking · p. 8
  • Satellite-based ADS-B can help track aircraft in shaded areas, improving safety and air-traffic control with real-time flight-sensor information.The passage contrasts this with existing terrestrial tracking and notes that recent major aircraft disappearances occurred in shaded areas.Source: 2) Asset Tracking · p. 8
  • Spire provides AIS, ADS-B, and weather datasets, while KLEOS uses LEO radio-frequency mapping to locate devices and detect obscured maritime activity.KLEOS describes its approach as a kind of reverse GPS; it may help locate ships disconnected from transponders and identify activity such as illegal fishing and trafficking.Source: 2) Asset Tracking · p. 8

3) Scientific and Environmental Missions: · 4) Government Space Programs:

NGSO small satellites support scientific, environmental, and educational missions whose payloads depend on mission objectives, while widening access to government space programs. Their uses range from monitoring and emergency response to space exploration, with AI anticipated to improve satellite-network management.

3) Scientific and Environmental Missions:

  • Mission objectives determine satellite payloads, and NGSO small satellites support weather research, including storm tracking and forecast improvement through NASA’s RainCube testing project,,.RainCube is testing the location, tracking, and analysis of rain and snowstorms worldwide.Source: 3) Scientific and Environmental Missions · pp. 8–9
  • NGSO satellites can monitor crops to improve harvest control and product quality, identify crop diseases, and analyze drought impacts,.Source: 3) Scientific and Environmental Missions · p. 9
  • Small satellites enable scientific experiments beyond Earth and environmental efforts such as detecting forest fires and oil spills, tracking melting ice and marine life, and combating desertification.Source: 3) Scientific and Environmental Missions · p. 9

4) Government Space Programs:

  • Small satellites have broadened access to space programs beyond a handful of countries, enabling companies, startups, and countries to launch or expand programs with aims from national security to emergency response.Source: 4) Government Space Programs · p. 9
  • For signals intelligence, small satellites can monitor electromagnetic spectrum activity, characterize communications traffic, detect interference, and locate unauthorized emissions.Source: 4) Government Space Programs · p. 9
  • During disasters such as earthquakes, tsunamis, or hurricanes, small satellites can rapidly assess damage and help coordinate relief and rescue teams.Source: 4) Government Space Programs · p. 9
  • Small satellites support space-threat research, including ESA’s Hera asteroid-diversion project, and exploration, as NASA’s InSight sent nanosatellites to relay real-time telemetry of its Mars landing.Source: 4) Government Space Programs · p. 9
  • Future satellite systems may use AI for automatic constellation management and intelligent ground-station networks that optimize control and operation.The paper presents these advances as anticipated opportunities for NewSpace and NGSO systems.Source: 4) Government Space Programs · p. 9

III. NGSO COMMUNICATION PROSPECTS … 2) Link Budget:

The survey reviews NGSO physical and radio-access technologies, including antenna systems and link budgets, and describes advantages and challenges associated with satellite mobility.

III. NGSO COMMUNICATION PROSPECTS

  • Satellite systems can extend coverage to remote communities, while NGSO constellations require autonomous, reconfigurable architectures without persistent ground-station contact.The subsection reviews physical/link procedures, antenna systems, link budgets, inter-satellite connectivity, waveform design, and link diversity and multiplexing.Source: §III · p. 9, A. Physical and Radio Access Aspects · p. 9

1) Antenna Systems:

  • NGSO multi-beam and phased-array antennas provide many higher-gain small beams to increase coverage-area capacity, while frequency and polarization are reused across beams.Direct-radiating arrays offer wide scan angles and lower off-boresight scan loss than phased arrays; antenna choice also depends on orbit, frequency, beam size, flexibility, edge-of-coverage gain roll-off, and cost.Source: 1) Antenna Systems · p. 10
  • Active antenna systems enable flexible multi-beam payloads, massive MIMO, controllable baseband antenna ports, and flexible beamforming for moving terminals and multi-orbit interoperability.They provide greater spatial degrees of freedom than passive antennas.Source: 1) Antenna Systems · p. 10
  • Low-cost electronic flat-antenna arrays can rapidly track and switch between satellites and constellations, using beam steering and interference nulling to exploit multiple constellations.They are expected to broaden NGSO connectivity with little installation, configuration, or maintenance effort.Source: 1) Antenna Systems · p. 10
  • Massive MIMO can raise degrees of freedom and spectral efficiency, but side-lobe interference requires suppression; cell-free MIMO and AoA are identified as promising extensions.The passage notes limited NGSO MIMO studies and calls for work on architecture, channel estimation, precoding, and inter-user interference.Source: 1) Antenna Systems · p. 10

2) Link Budget:

  • Up to 16 dB: LEO outperforms GSO in VSAT uplink, while handheld CNR is better on LEO than GSO.The comparison considers handheld terminals in S-band and VSAT terminals in Ka-band; both links have good VSAT link budgets.Source: 2) Link Budget · p. 10
  • About 36 times lower: at 600 km, LEO round trip delay (RTD) is lower than GSO's.The passage identifies lower signal losses and propagation delays as NGSO-link advantages that may support smaller equipment, lower terminal power, higher spectral efficiency, latency-critical applications, and commercial off-the-shelf devices.Source: 2) Link Budget · pp. 10–11
  • NGSO satellite mobility causes variable receive power, Doppler-related channel-estimation overhead, and time-varying satellite visibility.Proposed mitigations include channel-variation tracking, statistical Doppler characterization, constellation planning, and time-varying visibility matrices.Source: 2) Link Budget · p. 11

3) Inter-satellite Links: · 4) Waveform Design:

The sections survey inter-satellite link media and optical-link developments, then review satellite waveform standards and the challenges of adapting NGSO systems to 5G-NR.

3) Inter-satellite Links:

  • ISLs enable real-time or near-real-time command, control, communication, and information processing while reducing ground-station dependence; RF is mature and easier to track but more interference-prone and lower-rate than optical links.Source: 3) Inter-satellite Links · p. 11
  • Space-based THz links can avoid atmospheric attenuation and support high-speed, long-distance satellite connections, but high-power transmitters and low-noise receivers remain technological challenges.Source: 3) Inter-satellite Links · p. 11
  • FSO offers higher data rates, smaller size, and lower power than RF, with more complex tracking; experiments span satellite, ground-space, and aircraft-GSO links, and coherent modulation has been studied for LEO links.Source: 3) Inter-satellite Links · pp. 11–12
  • EDRS uses optical ISLs for multi-orbit data relay, while CCSDS specifications address coding and synchronization, including O3K direct-to-Earth links rated from a few Mbps to 10 Gbps,,.Source: 3) Inter-satellite Links · p. 12
  • Future space-based FSO research can explore QKD and fiber-optics techniques such as coherent modulation, multiplexing, coherent receivers, and advanced DSP, especially for atmospheric ground-space links.Source: 3) Inter-satellite Links · p. 12

4) Waveform Design:

  • DVB-S2(X) is widely implemented for satellite communications and selects modulation and coding schemes by link SNR; GSO waveform work also targets transmitter-side inter-beam interference management and precoding,,.Source: 4) Waveform Design · p. 12
  • NGSO 5G use cases drive candidate waveforms, but variable delay, high Doppler, and nonlinear degradation complicate NR; ESA and 5G Space Communications Lab projects investigate enabling technologies and emulation,,.Source: 4) Waveform Design · p. 12
  • Studies examine 5G NR waveforms and numerologies, NTN random access, impairment adaptability, physical/MAC effects, and handheld mmWave broadband feasibility; they identify unresolved challenges for NGSO integration –.Source: 4) Waveform Design · p. 12

5) Access Design and Multiplexing:

NGSO radio access must accommodate heterogeneous users and changing satellite links while balancing collisions, interference, capacity, QoS, and terminal power constraints. The section surveys random and coordinated access, emerging massive-access needs, and techniques for combining satellite links.

Access Design and Multiplexing

  • Satellite access must handle users’ relative motion, variable propagation delay and link availability, uneven transmit powers, and differing QoS profiles while providing fair access and scheduling.These conditions make radio access design for ground and airborne users more complex than in terrestrial networks.Source: 5) Access Design and Multiplexing · p. 12
  • Coordinated access allocates dedicated non-interfering resources for high-throughput, high-QoS users, while random access suits power-constrained terminals with limited visibility and lower data-rate or QoS needs.Random access lets users transmit independently over a shared medium; coordinated access typically relies on a central unit such as a ground station.Source: 5) Access Design and Multiplexing · p. 13

Random Access

  • Slotted satellite ALOHA studies address throughput, packet loss, diversity with interference cancellation, high-dynamic preambles, and IoT throughput,,,.Unslotted satellite IoT approaches include spread-spectrum ALOHA, LoRa, and Sigfox; proposed advances include orthogonal LoRa, LEO-adaptive LoRa MAC, and spread-spectrum ALOHA with SIC,,,,,.Source: 5) Access Design and Multiplexing · p. 13

Coordinated Access

  • Coordinated paradigms divide resources by frequency, time, code, or spatial beamforming; SDMA uses directional beams to mitigate inter-user interference.NOMA grants simultaneous access through non-orthogonal resources.Source: 5) Access Design and Multiplexing · p. 13
  • Satellite access research includes distributed small-satellite CSMA and TDMA/CDMA, QoS-aware scheduling for LEO satellites, and power- and bandwidth-aware SDMA for mobile users.The surveyed work also applies terrestrial wireless mesh-network concepts to satellite nodes and space missions.Source: 5) Access Design and Multiplexing · p. 13
  • NOMA with receiver-side SIC can exploit near-far effects in multi-layer, multi-orbit NGSO systems to reduce co-channel interference, serve more terminals, and improve spectral efficiency,.Studies consider capacity optimization in multi-beam systems and average AoI in LEO satellite-terrestrial networks while accounting for transmission, queuing, and propagation delays.Source: 5) Access Design and Multiplexing · pp. 13–14

Massive Access

  • Massive access is proposed for user volumes that can overwhelm random access with collisions and coordinated access with management overhead; MIMO beamforming requires multi-user detection such as SIC or joint satellite processing,,.Scaling access while accounting for relative motion, variable QoS, differential delays, and Doppler remains an open research direction.Source: 5) Access Design and Multiplexing · p. 14

Link Aggregation and Scalability

  • When a terminal sees multiple NGSO satellites, carrier aggregation can combine their signals to improve aggregated data rate, beam-load balancing, and link robustness through path diversity,.For NGSO scalability, dynamic beamforming can improve link performance; FSO and THz bands are envisioned for high-data-rate inter-satellite links, and NOMA, MIMO, and carrier aggregation can provide radio access to large user numbers.Source: 5) Access Design and Multiplexing · p. 14

B. Networking Aspects … 3) Software-defined Networking:

The networking discussion presents space information networks (SINs) as a way to extend satellite connectivity through cooperation across platforms, while emphasizing the routing, backhauling, and control challenges posed by dynamic, complex networks. It surveys SDN as a potential management approach but notes the need for flexible architectures suited to multi-layer networks and small satellites.

B. Networking Aspects

  • Using inter-satellite and inter-orbit links, SINs can extend connectivity while reducing reliance on costly gateways, especially where gateway sites are difficult to acquire.The expansion must contend with restricted spectrum, energy, and orbit resources.Source: B. Networking Aspects · p. 14

1) Space Information Networks:

  • SINs integrate GSO and NGSO satellites and HAPS for real-time communication, data services, routing, coverage, and coordination, but require complex load balancing and low-delay path selection.They can also help different satellite systems coexist without harmful interference.Source: 1) Space Information Networks · p. 14
  • ESA’s EDRS relays data between GSO and NGSO assets, while NASA’s SMN targets near-Earth applications; other proposals explore multi-orbit routing and satellite fog nodes.Source: 1) Space Information Networks · p. 15

2) In-space Backhauling:

  • In-space backhauling and Layer 3 routing make satellites active network elements, requiring traffic distribution that controls congestion and improves resource use, energy efficiency, and resilience.Source: 2) In-space Backhauling · p. 15
  • Backhaul protocols must account for changing topology, bandwidth, link delay, service traffic profiles, and node compute and storage capabilities amid dense networks, delays, QoS priorities, and uneven flows.Source: 2) In-space Backhauling · p. 15
  • NGSO backhaul can support urban 5G small cells through centralized traffic offloading, edge processing, and resource sharing, with capacity shaped by satellite selection and optimization –.3GPP standardization efforts address requirements and solutions for NR-NTNs.Source: 2) In-space Backhauling · p. 15

3) Software-defined Networking:

  • SDN offers reactive end-to-end traffic engineering across terrestrial and satellite segments, avoiding the topology and routing-table burden of traditional schemes [25],.Source: 3) Software-defined Networking · p. 15
  • Prior SDN designs place controllers on the ground,, GSO satellites, or across GSO, terrestrial infrastructure, and HAPS, but small-satellite solutions remain limited and often terrestrial-dependent.Multi-layer SINs need more flexible SDN architectures to handle node dynamics and heterogeneous traffic.Source: 3) Software-defined Networking · pp. 15–16

4) Network Slicing: · C. System and Architectural Aspects · 1) Resources Management and Optimization:

The survey frames NGSO management as a challenge shaped by limited payload resources, rapidly changing constellation conditions, and heterogeneous services. It discusses network slicing, operational architectures, and resource-allocation strategies as approaches whose benefits depend on addressing complexity, interference, and coordination constraints.

4) Network Slicing:

  • Network slicing uses SDN and NFV to create virtualized end-to-end networks on shared infrastructure, supporting heterogeneous services and integration within a 5G ecosystem.The survey also describes multi-orbit satellite networks and software-defined networking as promising for resource use and management, with slicing and satellite networks enabling autonomous resource allocation.Source: 4) Network Slicing · p. 16
  • Applying network slicing to NGSO remains challenging because dedicated slice spectrum can reduce multiplexing gains, and infrastructure information sharing can expose security vulnerabilities.The survey notes that slicing remains at an early stage in 5G and needs new algorithms and solutions for NGSO.Source: 4) Network Slicing · p. 16

C. System and Architectural Aspects

  • NGSO operations require more gateways and joint satellite reconfiguration as constellations move and traffic demand varies geographically.Unlike the described GSO operating model, NGSO operations must coordinate multiple satellites to optimize service; inter-satellite links can partly mitigate mega-constellation gateway CAPEX.Source: C. System and Architectural Aspects · pp. 16–17
  • Centralized control can improve network management but increases complexity, OPEX, and control-channel bandwidth needs; decentralized control risks losing global optimality.Decentralized operation requires energy-efficient, delay-sensitive onboard algorithms that limit message exchanges.Source: C. System and Architectural Aspects · p. 17
  • NGSO resource strategies must account for heterogeneous resources and dynamic propagation, alongside interference coordination, spectrum sharing, and security threats from large constellations.The survey identifies these as system requirements for smooth and reliable NGSO communications.Source: C. System and Architectural Aspects · p. 17

1) Resources Management and Optimization:

  • NGSO resource allocation must balance power, bandwidth, time, beams, and antennas despite smaller payloads and fast-changing, often non-convex optimization problems.The survey suggests reducing optimization parameters or using low-complexity metaheuristics and machine-learning methods when iterative solutions are impractical.Source: 1) Resources Management and Optimization · p. 17
  • Spot beams simplify coverage but increase handovers, whereas hybrid wide-spot beams reduce handovers; joint beam and resource optimization can balance handover frequency and demand.In the hybrid scheme, steering beams track users and handovers occur between wide beams of adjacent satellites.Source: 1) Resources Management and Optimization · p. 17
  • Overlapping satellites can compete for the same demand, causing interference and wasted resources, while spectrum blocks vary with availability, speed needs, and service or user priority.Jointly optimizing adjacent satellites increases complexity, and fast handovers can make traditional frequency reuse infeasible.Source: 1) Resources Management and Optimization · p. 17

2) Interference Management: · 3) Spectrum Sharing:

Interference management must address aggregated, heterogeneous NGSO interference, including inter-satellite links, while spectrum sharing offers priority-based ways for NGSO systems to coexist with GSO systems. The sections review mitigation approaches and sharing scenarios.

2) Interference Management:

  • NGSO interference analysis must account for aggregation from many multibeam satellites using frequency reuse; deployment heterogeneity and ambiguity make traditional mitigation effectiveness uncertain.The discussion notes that emerging constellation properties and interference interactions require thorough analysis across bands and constellations.Source: 2) Interference Management · pp. 17–18
  • Existing spectrum regulations may not ensure GSO protection from NGSO interference; studied mitigations include look-aside, band splitting, and exclusion zones.Band splitting may work against maximizing spectral efficiency.Source: 2) Interference Management · p. 18
  • [212] studies Ka-band LEO/GSO exclusion angles, proposes power control and inter-site distance, and examines NGSO-NGSO throughput and Ka/V-band band splitting.These works address distinct interference settings, motivating analysis across heterogeneous constellations and bands.Source: 2) Interference Management · p. 18
  • ISL interference remains underexplored beyond overlapping coverage and is complicated by constellation motion; studies examine LEO-ISL effects, code-aided suppression, and optical links’ interference robustness.ISL interference may occur wherever inter-satellite communication takes place, not only where coverage areas overlap.Source: 2) Interference Management · p. 18

3) Spectrum Sharing:

  • NGSO-GSO spectrum sharing addresses mega-constellations’ use of GSO Ka- and Ku-band frequencies, with GSO as licensed primary and NGSO as lower-priority secondary using underlay, overlay, or interweave.Coordination and awareness of counterpart systems’ operating characteristics are described as essential for successful sharing.Source: 3) Spectrum Sharing · p. 18
  • Interweave senses for idle spectrum, underlay constrains NGSO power to meet GSO interference thresholds, and overlay cooperatively relays primary traffic in exchange for access without stringent power limits.The approaches are described in,,, and, respectively.Source: 3) Spectrum Sharing · p. 18
  • Integrating these spectrum-sharing paradigms into NGSO communications can improve spectral efficiency and transmission reliability.Source: 3) Spectrum Sharing · pp. 18–19
  • Proposed approaches include database coordination, LEO throughput optimization subject to GSO QoS, concurrent overlay/underlay access, and LEO beam-hopping access to GSO spectrum.Source: 3) Spectrum Sharing · p. 19

4) Secure Communications: · IV. NGSO DEPLOYMENT CHALLENGES · A. Regulatory and coexistence issues

NGSO security must address threats beyond satellite–ground links, including satellite-to-satellite communications and internal satellite structures. Deployment also faces interference and regulatory challenges as constellations densify and coexist with GSO and other NGSO systems.

4) Secure Communications:

  • Security research must extend beyond satellite–ground data links to satellite-to-satellite communications, satellite internals, and application-specific security analysis.Space-based networks introduce security risks that deserve more attention than the traditional focus on uplink and downlink protection.Source: 4) Secure Communications · p. 19
  • Eavesdropping, jamming, spoofing, and denial-of-service attacks threaten NGSO systems, with limited satellite processing power making message-flooding especially disruptive –.Intelligent protocol-exploiting jamming is a concern for massive uncoordinated access; a DoS overload can prevent service within a satellite’s short visibility window.Source: 4) Secure Communications · p. 19
  • Cryptography-based security carries high computational complexity, while QKD key exchange may be too slow for fast-moving LEO satellites and BCT introduces satellite-node database storage and distribution challenges –.QKD can detect eavesdropping or modification; BCT can authenticate satellite and ground-station identities and communication patterns, helping protect against DoS, DDoS, and insider attacks.Source: 4) Secure Communications · p. 19
  • Physical-layer security avoids added encryption/decryption complexity, but limited satellite-link spatial diversity constrains its use, while joint precoding across overlapping NGSO coverage areas may improve secrecy.The approach is still in its infancy for satellite communications; adjacent-satellite antennas may provide exploitable spatial diversity.Source: 4) Secure Communications · p. 19

IV. NGSO DEPLOYMENT CHALLENGES

  • NGSO deployment challenges include constellation and architecture design, coexistence, operations, and user equipment, while NTN integration adapts satellite networks to terrestrial technologies.3GPP Release 17 provides initial mechanisms and specifications for NTNs complementing 5G; satellites may serve as relays, access points, or backbone/backhaul support.Source: §IV · p. 20

A. Regulatory and coexistence issues

  • Densifying, heterogeneous NGSO constellations create unprecedented GSO–NGSO interference challenges, and ITU EPFD limits constrain emissions in GSO-allocated bands,,.Aggregate emissions from NGSO satellites motivated EPFD beyond single-entry PFD limits; operator tools and simulators assess compliance, while discrimination angles and exclusion zones can limit interference –.Source: A. Regulatory and coexistence issues · pp. 20–21
  • Regulators are adapting NGSO rules: WRC-15 raised concerns about FSS filings under Article 22 EPFD limits and No. 9.7B coordination, while WRC-19 agreed on a Q/V-band framework,.A WRC-23 agenda item was planned to study space-to-space links; NGSO Earth-station deployments also require careful shared-spectrum design, and the FCC has proposed Ka-band allocation, power-limit, and service-rule updates for NGSO FSS terminals.Source: A. Regulatory and coexistence issues · pp. 20–21
  • Large NGSO constellations may interfere with other NGSO networks, although preliminary Ka- and V-band analysis found relatively low risk; mitigation may be needed when interference is unacceptable,.ITU priority for inter-constellation coordination is based on filing date, while spectrum sharing must also avoid degrading GSO service.Source: A. Regulatory and coexistence issues · p. 21

B. Satellite Constellation Design · C. User Equipment

NGSO constellation design must adapt to uneven, uncertain demand, while user equipment must track rapidly moving satellites affordably and support integration with terrestrial and 5G networks. Flexible deployments and antenna advances address these needs, but design and implementation challenges remain.

B. Satellite Constellation Design

  • Constellation parameters include orbit type, altitude, orbit and satellite counts, and phase factor; established polar and Walker-Delta patterns overlook demand, motivating staged flexible deployment toward high-demand regions.Flower constellations likewise organize satellites by shared Earth-fixed trajectories, while the passage argues that demand-responsive deployment better addresses non-uniform and uncertain global demand.Source: B. Satellite Constellation Design · pp. 21–22
  • Reconfigurable constellations enable area-specific observation but require energy-intensive maneuvering; hybrid multilayer circular-elliptical designs accommodate heterogeneous traffic, and lifecycle-cost optimization across spatial-temporal demand scenarios is proposed.Hybrid designs still face the challenge of adapting to growing demand areas.Source: B. Satellite Constellation Design · p. 22
  • Regional constellations use fewer satellites and may match or exceed global-coverage performance; multiple NGSO satellites can provide redundancy and avoid overlapping beams, but optimal regional patterns remain underexplored.Design must optimize orbital characteristics such as altitude and inclination for asymmetric, time- and space-varying coverage requirements.Source: B. Satellite Constellation Design · p. 22

C. User Equipment

  • Closer, lower-altitude satellites reduce latency but move faster across user terminals, requiring tracking and handover; costly gimbaled LEO equipment limited past broadband rollout, making inexpensive terminals essential.AST & Science envisioned a space-based cellular broadband network that lets standard smartphones roam automatically between land and space networks.Source: C. User Equipment · p. 22
  • Electronic beam steering is gaining momentum as an alternative to mechanically steered parabolic antennas; smart digital arrays [263] and single-terminal multi-satellite tracking can support multi-orbit operation while reducing duplicated circuitry.The passage identifies low-cost, high-performance tracking antennas as an important prospective development and names companies developing products.Source: C. User Equipment · p. 22
  • Electronically steerable flat panels offer a more agile, affordable, scalable option that can extend NGSO services to small terminals and mobile assets; flexible satellites with onboard processing can form focused high-power beams.Parabolic antennas are expected to remain common in government institutions and large moving platforms such as cruise ships.Source: C. User Equipment · pp. 22–23
  • 3GPP integration enables handheld users to be served by LEO and GSO in S-band, while high-gain VSAT or phased-array users can use S- and Ka-band.NTN-compatible 5G must address long delays, large Doppler shifts, moving cells, and synchronization; specified VSAT equipment uses a circularly polarized phased array with 60 cm equivalent aperture, versus a linearly polarized omnidirectional handheld antenna.Source: C. User Equipment · p. 23

D. Operational Issues · V. FUTURE RESEARCH DIRECTIONS AND OPPORTUNITIES · A. Open RAN

NGSO systems are presented as a route to more flexible, globally connected communications, but their deployment raises sustainability concerns and depends on addressing technical and operational challenges. Open RAN could improve satellite-network adaptability, while its compatibility and data requirements need careful analysis.

D. Operational Issues

  • Rough estimates suggest more than 50,000 satellites could be added to Earth orbits, heightening concerns about defunct satellites, debris, and collision risks.Research examines constellation impacts, debris retrieval and relocation to graveyard orbits, and pulsed lasers to hasten debris re-entry.Source: D. Operational Issues · p. 23
  • Visible LEO satellites could jeopardize ground-based astronomy through light pollution, while proposed mitigations include smaller, less reflective satellites and accurate orbit data for avoidance zones.The astronomy community warns that visible satellites could outnumber visible stars and affect research in optical and radio wavelengths; the international research community seeks a role in decisions to mitigate these impacts.Source: D. Operational Issues · p. 23
  • Information sharing among regulators, astronomers, and industry could support sustainability standards, building on ITU protections for radio astronomy and existing astronomy-community advocacy.The United Nations working group on the long-term sustainability of space is offered as a model for progress.Source: D. Operational Issues · p. 23

V. FUTURE RESEARCH DIRECTIONS AND OPPORTUNITIES

  • NGSO satellites are envisioned as converging with wireless systems to provide ubiquitous coverage, hybrid connectivity, and capacity, while opening digital-innovation opportunities beyond connecting poorly served areas.Source: §V · p. 24

A. Open RAN

  • Open RAN disaggregates the RAN into functional parts with standardized interfaces, vendor-independent hardware, and open software, and has entered 3GPP standardization.The Open RAN Alliance promotes these initiatives.Source: A. Open RAN · p. 24
  • Open RAN could let satellite networks exchange components or add infrastructure as traffic and service requirements change, unlike inflexible single-manufacturer systems.This is especially relevant to missions lasting more than 10 years, when satellite hardware is difficult to replace.Source: A. Open RAN · p. 24
  • An AI/ML-driven Open RAN management strategy proposes policy definition and resource management to support computationally intensive tasks and network-triggered decisions,.Source: A. Open RAN · p. 24
  • For NGSO networks, Open RAN could enable flexible constellation extensions and non-proprietary hardware or software updates, but diverse hardware compatibility and data handling require careful design.Resource management, carrier planning, and network adaptation are key use cases; multi-layer mega-constellations appear especially demanding, and the cost of added flexibility needs analysis.Source: A. Open RAN · p. 24

B. Broadband Connectivity for Space Missions … E. IoT via NGSO Satellites

The sections describe NGSO as enabling continuous space-mission connectivity, edge processing, space-based cloud storage, and wide-area IoT. They also identify unresolved operational, resource-management, and integration challenges.

B. Broadband Connectivity for Space Missions

  • Direct Internet access through a higher-orbit space-based provider could keep small downstream satellites connected, reduce ground-station needs, and enable real-time, reliable communications.The existing reliance on distributed ground stations and limited access sessions constrains continuous mission operations and high-throughput data downlinking.Source: B. Broadband Connectivity for Space… · pp. 24–25
  • Space-based Internet could coordinate constellations and relay TT&C between small-satellite terminals and the ground NCC, but requires complex routing and load balancing.Challenges include finding shortest-delay paths and handling dynamic nodes, high relative speeds, and frequent handovers; these areas remain unexplored.Source: B. Broadband Connectivity for Space… · p. 25

C. Edge Computing

  • Because satellite processors have limited capacity, NGSO edge computing and computation offloading – could process data near users and reduce network traffic and delay.Distributed processing can shift tasks from a central unit such as a GSO satellite to NGSO satellites, but practical limitations and requirements remain unclear.Source: C. Edge Computing · p. 25

D. Space-based Cloud

  • Space-based cloud storage over NGSO satellites can resist natural disasters on Earth and support flexible global data sharing, with faster transfers than terrestrial clouds for delay-sensitive services.The cited advantages also include avoiding geographical boundaries and terrestrial obstacles.Source: D. Space-based Cloud · p. 25
  • SpaceBelt plans distributed LEO data-storage servers, but sporadic ground-station contact and limited satellite power make energy-efficient, demand-responsive downloads difficult to schedule.Terrestrial cloud task-scheduling algorithms do not apply to these space-based infrastructures.Source: D. Space-based Cloud · p. 25

E. IoT via NGSO Satellites

  • NGSO flexibility, scalability, and shorter propagation distances can support small, long-life, low-power IoT terminals and lower-cost wide-area services than GSO satellites.These properties are presented as enabling a universal network of worldwide interconnected devices.Source: E. IoT via NGSO Satellites · p. 25
  • 3GPP Release 17 studied NB-IoT adaptations for satellite NTN, while NGSO protocol work accounts for satellite motion –; seamless device connectivity and ultra-reliable low-latency service remain open challenges.The research progress is described as early-stage, with integration needed for both mobile and stationary IoT devices.Source: E. IoT via NGSO Satellites · p. 25

F. Caching Over NGSO Satellites · G. Aerial Platforms and NGSO Coordination · VI. CONCLUSIONS

The survey reviews NGSO communication technologies, architectures, integration challenges, and research directions, including caching and coordination with aerial platforms. It highlights NGSO’s potential to extend coverage and capacity, enable low-latency services, and support integrated space-air-ground networks.

F. Caching Over NGSO Satellites

  • NGSO satellites can cache and multicast content near users, updating cached data across locations to reduce repeated transmissions, save spectrum, and lower transmission delay.A hybrid federated content delivery network can exploit satellite-terrestrial complementarity to improve user experience.Source: F. Caching Over NGSO Satellites · pp. 25–26
  • Caching placement over NGSO must account for changing topology and limited onboard resources, while targeting fast convergence and low complexity.Combining caching with edge computing can integrate data processing, content analysis, and caching.Source: F. Caching Over NGSO Satellites · p. 26

G. Aerial Platforms and NGSO Coordination

  • UAVs and HAPS can extend coverage and capacity and relay satellite-terrestrial links, while low-latency NGSO—especially LEO—can support UAV autonomy –.Aerial platforms are described as flexible and offering strong line-of-sight connectivity.Source: G. Aerial Platforms and NGSO… · p. 26
  • Integrated NGSO, UAV, and HAPS networks face coordination, navigation, and synchronization challenges, including Doppler shifts, pointing errors, outdated CSI, topology control, and multi-hop routing.Investigated signaling approaches include FSO, RF, and hybrid signaling –.Source: G. Aerial Platforms and NGSO… · p. 26
  • NGSO’s envisioned roles include global low-latency broadband, edge computing and caching, space-based cloud storage, and real-time services through integrated satellite, aerial, IoT, and terrestrial systems.Integrated systems are also envisioned to support massive data transmission and systematized information services.Source: G. Aerial Platforms and NGSO… · p. 26

VI. CONCLUSIONS

  • NGSO deployments are driven by reduced free-space attenuation, low-profile antennas, small propagation delay, lower per-satellite injection cost, and potential to increase terrestrial coverage and capacity.The survey notes growing technology development, interest, and investment supporting NGSO communications.Source: §VI · p. 26
  • The survey spans NGSO physical-layer and radio-access technologies, networking, system architectures, integration challenges, and research directions.It reviews multi-orbit connectivity, antennas, waveforms, link diversity and multiplexing, networking, resource optimization, interference, spectrum sharing, and security.Source: §VI · p. 26
  • The survey examines GSO coexistence, constellation design, resource management, and user-equipment challenges, and identifies research directions for reliable, efficient global satellite communications.It aims to encourage further investigation of NGSO communication and deployment challenges.Source: §VI · pp. 26–27

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