5G

Non-Terrestrial Networks in 3GPP Release 18 for Global IoT Expansion

03 Feb

Introduction to IoT over NTN in 3GPP Release 18

3GPP Release 18 marks significant enhancements in the domain of IoT connectivity, particularly through Non-Terrestrial Networks (NTN). This release marks the first instance where LTE and NR standards explicitly incorporate support for NTN, expanding the reach of IoT and eMTC devices beyond terrestrial constraints. With Release 18, there is a focused effort to leverage a constellation of satellites—ranging from LEO to GEO orbits—and High-Altitude Platform Stations (HAPS) to establish a resilient and ubiquitous link access for IoT devices.

This integration is pivotal for ensuring consistent and reliable connectivity across diverse geographical landscapes, including remote and rural areas previously underserved by traditional network infrastructures. The technical discourse will navigate through the intricacies of adapting current cellular technologies to the unique challenges posed by NTN—such as latency, frequency offsets, and the dynamic nature of satellite movement—laying the groundwork for a new era of global IoT communication.

Definition of NTN

Non-Terrestrial Networks (NTN) harness satellites in Low Earth Orbit (LEO), Medium Earth Orbit (MEO), and Geostationary Orbit (GEO) to extend connectivity beyond terrestrial bounds. LEO satellites, closest to Earth, provide low latency and are ideal for time-sensitive communications. MEO satellites, stationed further out, offer a balance between coverage area and latency, suitable for navigation and broader communications. GEO satellites, positioned over the equator at 35,786 kilometers, ensure continuous coverage over specific areas, making them perfect for broadcast and weather monitoring.

3GPP’s Non-Terrestrial Network (NTN) initiative is set to revolutionize satellite communications, especially through LEO satellites positioned over 600 km high and the stationary GEO satellites.

An innovative structural design has been proposed for the implementation of satellite communication systems adhering to the 3GPP NTN framework. Typically, communication from the satellite to the core network on the ground happens through a feeder link connected to a satellite ground station. This setup then extends communication capabilities to individual user devices via a dedicated service link.

 

Figure 1: Communication Framework for IoT over NTN

 

The diagram illustrates the communication framework of Non-Terrestrial Networks (NTN) utilizing satellites in Low Earth Orbit (LEO) and Geostationary Orbit (GEO). IoT devices connect via 5G NB-IoT user links to LEO satellites, which are capable of directly relaying data through intersatellite links. These satellites also link to GEO satellites, which provide a broader coverage area. The flow of data is directed through feeder links to ground stations, which then facilitate the connection to the internet or direct network connections.

This infrastructure benefits from 3GPP Release 18 enhancements that bolster power efficiency, enable better mobility support, and optimize signaling for a more reliable and efficient IoT communication experience.

Main Enhancements from 3GPP Release 18

In 3GPP Release 18, enhancements are geared towards optimizing IoT operations over Non-Terrestrial Networks (NTN) with a focus on efficiency, coverage, and performance:

  • Support for Half-Duplex in FDD Bands: IoT devices over NTN in Release 18 are expected to support half-duplex operations, conserving power, and simplifying device design.
  • Regulatory Compliance for UE Location: Release 18 emphasizes the importance of network verification of UE locations to meet regulatory standards, ensuring accurate and reliable location reporting.
  • Enhanced Mobility for IoT Devices: Measurement protocols will be enhanced to prevent radio link failures and support mobility, particularly for eMTC devices, building on the mobility enhancements from Release 17.
  • Throughput Improvements: Addressing HARQ stalling issues by potentially disabling HARQ feedback for downlink to enhance IoT NTN performance, especially in terms of throughput.
  • Optimized GNSS Operation: GNSS use will be optimized for power efficiency, allowing for longer connections without requiring constant GNSS fixes, thus conserving battery life in IoT devices.
  • Specification of Core and Performance Requirements: RF, RRM, and demodulation requirements, unspecified in Release 17, will be detailed in Release 18 to support NB-IoT and eMTC operations over NTN.

 

Expanding NR NTN to Higher Frequency Bands

The strategic expansion of NR NTN into frequencies above 10 GHz, notably the Ka band, in 3GPP Release 18, introduces a revolutionary development for IoT and mobile broadband services via non-terrestrial channels.

This move is primarily aimed at enhancing the capabilities of Very Small Aperture Terminal (VSAT) devices, enabling them to support broadband data services across various platforms, including maritime, airborne, and terrestrial vehicles.

The shift to the Ka band brings several technical challenges and opportunities. One of the main challenges is the increased signal attenuation due to atmospheric conditions, which is more pronounced at these higher frequencies. This necessitates the development of advanced antenna technologies and adaptive modulation schemes to ensure reliable signal transmission and reception. The higher frequency also allows for narrower beam widths, leading to more focused and efficient use of the spectrum but requiring more precise beam steering and management.

For VSAT terminals, the Ka band offers the potential for higher data rates and enhanced network capacity. This is crucial for applications requiring significant bandwidth, such as high-definition video streaming, large-scale data transfers, and real-time communication services. However, the implementation of these systems in the Ka band requires careful consideration of power requirements, antenna design, and thermal management to maintain optimal performance.

Key broadband satellite providers deliver services to fixed, yet relocatable, user devices. GEO satellites provide broad coverage with fewer units needed, remaining stationary relative to Earth, unlike LEO satellites that move swiftly, necessitating constant tracking. LEO satellites, however, offer lower latency, higher throughputs due to their proximity to Earth, and greater capacity scalability with smaller beam sizes, although this requires more satellites to maintain coverage and service quality.

 

Current satellite spectrum allocations range from 1.5 GHz up to 51.4 GHz across what are known as the L, S, C, Ku, Ka, and Ku bands.

Figure 2: Satellite spectrum allocations range

 

The table below provides an overview of various satellite providers, their satellite systems and the spectrum used.

Table 1: Overview of some satellite providers

Operator Satellite system (deployed) Spectrum
Space X (Starlink) 12000+ (3580) Ku-band
OneWeb 648 (542) Ku-band
Kuiper 3236 (0) Ka band
Telesat 188 (2) C, Ku, Ka bands
Echostar 10 GEO (10) Ku, Ka, S bands
HughesNet 3 GEO (2) Ka band

Moreover, the use of higher frequency bands opens up new possibilities for network design and deployment in NTN scenarios. It allows for the accommodation of more users within a given spectral space, improving overall network efficiency and user experience. The integration of these high-frequency bands into the 5G NTN framework is a testament to the ongoing evolution of 5G capabilities, striving to provide ubiquitous, high-speed connectivity regardless of geographical and environmental constraints.

Advancements in UE Mobility and Service Continuity

In 3GPP Release 18, significant strides are made in enhancing User Equipment (UE) mobility and service continuity, particularly within Non-Terrestrial Networks (NTN). These advancements are crucial for maintaining seamless connectivity in the dynamic environment of NTN, where factors such as satellite movement and variable signal delays pose unique challenges.

Key improvements in this release include the development of sophisticated algorithms for handover and cell re-selection. These algorithms are designed to be highly responsive to the rapid changes in satellite positions, ensuring that UEs can swiftly switch between cells without service disruption. This is particularly important for maintaining consistent communication links in LEO, MEO, and GEO satellite systems, where the relative position of satellites to the earth’s surface changes frequently.

Another focus area is the enhancement of tracking area updates. As satellites move, the coverage areas of the cells they support also shift. The updated tracking area management ensures that UEs are always connected to the appropriate cell, improving the overall reliability of the network. This is complemented by refined protocols for signal measurement and assessment, allowing UEs to make more accurate decisions about when to initiate handovers.

Furthermore, the enhancements address the continuity of service between terrestrial and NTN cells. This involves optimizing the transition process, ensuring that UEs can switch between different types of networks seamlessly. This is critical for applications that require uninterrupted connectivity, such as emergency services, critical infrastructure monitoring, and certain industrial IoT applications.

Release 18’s focus on improving UE mobility and service continuity in NTN environments demonstrates 3GPP’s commitment to addressing the unique challenges of non-terrestrial communication, paving the way for more robust and reliable mobile networks.

Regulatory Compliance through Network Verification of UE Location

In 3GPP Release 18, a significant focus is placed on meeting regulatory compliance through precise network verification of User Equipment (UE) locations.

This involves the network’s ability to verify and report the location of UEs, which is crucial for emergency calls, lawful intercepts, public warnings, and billing processes accurately and reliably.

Table 2: Overview on Requirements for UE location verification

Service Accuracy Reliability Latency
Emergency Calls 50m Horizontal, 3m Vertical Provision of reliable UE location Quick location determination, not delaying call setup
Lawful Intercept (LI) Mapping to physical location with cell ID granularity UE-generated location info must be verifiable Should not impair LI service
Public Warning Service (PWS) Macro cell size granularity for targeted alerts Implied but not explicitly stated in regulations Should not significantly affect PWS delivery
Charging and Tariff Notifications Context knowledge of the UE for accurate charging Mobile operators must confirm UE location Should not affect charging services
All Regulated Services Protection of user location data Processing allowed for safety, crime prevention, or consent N/A

For emergency calls, the most stringent accuracy is required: 50m horizontally and 3m vertically, aligning with major regulatory bodies. Reliable location information is also critical for timely assistance and must not delay call setup.

Lawful intercepts require unambiguous mapping of logical to physical location, typically based on cell ID to detect border crossings.

Public warning services, which may utilize CellBroadcast for area-specific alerts, depend on reliable location information corresponding to cell size granularity.

Lastly, accurate UE context is essential for proper charging and tariff notifications.

Across all services, privacy and automated decision-making regulations necessitate safeguarding user location data, allowing its use for safety, crime prevention, and regulatory compliance.

The system now must contend with the additional complexities introduced by Non-Terrestrial Networks (NTN), such as longer signal delays and changing satellite positions. Enhanced algorithms are implemented to calculate accurate UE positions, factoring in the high latency and dynamic nature of NTN. This ensures compliance with stringent regulatory requirements for location accuracy and reliability, particularly in critical communication scenarios.

Improvements for IoT NTN Performance

The enhancements in IoT performance over Non-Terrestrial Networks (NTN) in 3GPP Release 18 focus on addressing key challenges such as High Automatic Repeat reQuest (HARQ) stalling. This issue is particularly pronounced in NB-IoT and eMTC due to the long round-trip times inherent in NTN. To mitigate this, strategies like disabling HARQ feedback for downlink data transmission are being explored. This approach is expected to significantly improve throughput.

Additionally, optimizations in the operation of Global Navigation Satellite Systems (GNSS) are being implemented. These improvements aim to facilitate sparse GNSS usage while maintaining efficient power consumption, ensuring longer-term connectivity for IoT devices in NTN environments.

Core and Performance Requirements for IoT over NTN

3GPP Release 18 sets out to define and complete the core and performance requirements for IoT operations over Non-Terrestrial Networks (NTN), an aspect not fully specified in the previous release. This includes detailing the Radio Frequency (RF), Radio Resource Management (RRM), and demodulation requirements for NB-IoT and eMTC operations in an NTN context. These specifications are crucial for ensuring consistent and reliable IoT device performance in the unique conditions of NTN, encompassing aspects like signal propagation characteristics, power efficiency parameters, and handling of variable latency and connectivity scenarios specific to NTN environments.

Conclusion

3GPP Release 18 is a pivotal development in IoT connectivity, embracing Non-Terrestrial Networks (NTN) to extend the reach of devices beyond terrestrial limits.

The main enhancements include half-duplex support in FDD bands for power conservation, improved mobility protocols to ensure service continuity amid the NTN dynamics, and throughput optimization to address HARQ stalling in NB-IoT and eMTC. Crucially, Release 18 also emphasizes regulatory compliance, with accurate UE location verification for emergency services, public warnings, and billing.

This compliance is coupled with advanced algorithms to overcome NTN challenges such as longer signal delays and satellite mobility. Additionally, Release 18 will finalize core RF, RRM, and demodulation requirements for IoT over NTN, ensuring reliable device performance across variable NTN conditions. These enhancements demonstrate a commitment to robust, reliable, and regulatory-compliant mobile networks, leveraging NTN for a new era of global IoT communication.

 

 

References

  • 3GPP TR 38.821, Solutions for NR to support Non-Terrestrial Networks (NTN)
  • 3GPP TR 38.882, Study on requirements and use cases for network verified UE location for Non-Terrestrial-Networks (NTN) in NR (Release 18)
  • 5G Americas, “Update on 5G Non-Terrestrial Networks”, July 2023.