Galileo and Additional Navigation Satellite Systems

Description

Galileo and Additional Navigation Satellite Systems (GANSS) is a standardized capability in 3GPP that defines how mobile devices and networks can leverage multiple Global Navigation Satellite Systems (GNSS) for enhanced positioning. While early cellular location services primarily relied on Assisted GPS (A-GPS), GANSS expands support to include the European Galileo system, Russia's GLONASS, China's BeiDou, Japan's QZSS, and Satellite-Based Augmentation Systems (SBAS) like WAAS and EGNOS. The technology works through assistance data provided by the network to the UE via control plane (e.g., LTE Positioning Protocol - LPP) or user plane protocols. This assistance data includes precise ephemeris, almanac, time synchronization, and ionospheric correction information for the supported GNSS constellations, which drastically reduces the Time To First Fix (TTFF) and improves sensitivity. The UE's GNSS receiver can then acquire signals from satellites across multiple systems simultaneously. By combining measurements (pseudoranges, carrier phase) from more satellites across different constellations, the positioning engine can achieve higher accuracy, better availability in urban canyons where view to a single constellation is obstructed, and increased robustness against interference. GANSS support is integrated into various network-based and UE-based positioning methods, including Assisted GNSS (A-GNSS), Standalone GNSS, and Real-Time Kinematic (RTK) positioning. Network elements like the Enhanced Serving Mobile Location Centre (E-SMLC) and Location Management Function (LMF) in 5G are responsible for generating and delivering the GANSS assistance data.

Purpose & Motivation

GANSS was developed to overcome the limitations of relying solely on the American GPS system for satellite-based positioning in mobile networks. Dependence on a single constellation posed risks related to service availability, geopolitical factors, and performance limitations in dense urban or indoor environments where satellite visibility is poor. The proliferation of other global and regional GNSS constellations (Galileo, GLONASS, BeiDou) presented an opportunity to significantly improve positioning performance. GANSS was created to standardize how these multiple systems are supported, ensuring interoperability between chipsets, handsets, and network infrastructure from different vendors. It solves critical problems for emergency services (e.g., E112 in EU), where reliable and accurate location is a matter of life and death, especially for calls made indoors. For commercial applications, it enables more accurate turn-by-turn navigation, location-based advertising, asset tracking, and supports emerging high-accuracy services for IoT, autonomous vehicles, and augmented reality. The historical motivation aligns with global efforts to create multi-GNSS environments for resilience and performance, which 3GPP standardized to ensure the mobile ecosystem could fully exploit these advancements.