Introduction:

A recent survey showed that Non-Terrestrial Networks (NTNs) are viewed by the telecom industry as reinforcing service reliability and adding an extra layer of network redundancy to 5G. This view increasingly makes the convergence of satellites and 5G (and fiber) a mainstream application in telecoms.  With LEO constellation service revenues forecast to reach $15 billion next year, the industry is expected to experience unprecedented growth.

However, that growth will depend on interoperability to realize economies of scale.  To achieve that goal NTN standards, regulatory and policy frameworks must evolve to keep pace and ensure equitable access to space for all. As such, we examine the status and future NTN work in 3GPP and ITU-R in this article.

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3GPP (3rd Generation Partnership Project) has established NTNs as a key part of 5G and future 6G by defining standards in Release 17, which introduced support for satellites and High-Altitude Platforms (HAPS) for direct-to-device (D2D) communication, enabling ubiquitous connectivity. Current work in Release 18 and beyond (including ongoing Release 19 studies) focuses on enhancing performance, expanding spectrum, improving security, and integrating NTNs seamlessly with terrestrial networks for better resource management, leading towards a unified, hybrid telecom ecosystem for global coverage.

• Release 15 & 16 (Foundational): Established NTN use cases, system architectures, and channel models for satellite-based systems.
• Release 17 (First Standardized Release): Introduced the first normative specifications for 5G NR and NB-IoT NTNs, covering GEO and LEO/MEO satellites, addressing technical hurdles like propagation delay and Doppler shift for mass-market devices.
• Release 18 (Enhancements): Studied security aspects, improved 5G NR NTN for higher frequencies (above 10 GHz), and focused on resource management for efficient integration.
• Release 19 & Beyond (Ongoing): Continues to evolve NTNs, introducing features like regenerative payloads, Ku-band support, and further integration for future 5G-Advanced and 6G networks, with studies on 6G architecture. 

• Hybrid Networks: Creating a unified framework for seamless terrestrial and non-terrestrial operation.
• Direct-to-Device (D2D) Evolution: Expanding services beyond basic IoT to support smartphones for voice and data in remote areas.
• Technical Refinements: Addressing RF performance, spectrum coordination, and operational complexity for LEO/MEO systems.
• 6G Foundation: Building architectural principles for ubiquitous connectivity that will underpin future 6G systems. 

The International Telecommunication Union Radiocommunication Sector (ITU-R) Working Party 4B is actively shaping NTN’s by developing reports and recommendations to integrate satellites (LEO, MEO, GEO) and High-Altitude Platforms (HAPs) with 5G and future 6G cellular networks. The aim is to enable ubiquitous coverage, Direct-to-Device (D2D) services, and seamless hybrid networks, with ongoing work focusing on radio interface specifications, spectrum harmonization, and performance enhancements for reliable connectivity.

• Standardization: ITU-R is finalizing Recommendation ITU-R M.IMT-2020-SAT.SPECS (based on 3GPP’s Release 17/18 specs) to standardize 5G satellite-to-ground communication, supporting IoT and advanced mobile services.
• Working Groups: WP 4B (Satellite services) and other groups are key to defining NTN requirements, spectrum usage, and interoperability.
• Focus Areas:
  • Hybrid Networks: Creating seamless service continuity between terrestrial and space/aerial segments.
  • Direct-to-Device (D2D): Enabling smartphones to connect directly to satellites.
  • Spectrum: Harmonizing spectrum for NTNs, including Ku-band, for expanded services.
  • Performance: Addressing challenges like Doppler shift, propagation delay, and handover management for LEO/MEO constellations. 

• 3GPP  is a crucial partner, introducing NTN frameworks in Release 17 (IoT) and Release 18 (enhanced 5G), with continuous updates for 6G and beyond, closely coordinating with ITU-R. 

• ITU-R’s reports discuss future trends, including AI-driven interfaces, diverse terminals (wearables, implants), and the role of NTNs in achieving global, resilient connectivity, supporting Sustainable Development Goals (SDGs). 

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