Description
The Wide Area Augmentation System (WAAS) is a regional satellite-based augmentation system (SBAS) primarily operated by the Federal Aviation Administration (FAA) to improve the performance of Global Navigation Satellite Systems (GNSS), like GPS, over North America. Within 3GPP specifications, WAAS is referenced as a supported positioning method for User Equipment (UE), enabling more accurate and reliable location determination. The system works by deploying a network of ground reference stations that monitor GPS satellite signals. These stations collect data on errors caused by ionospheric disturbances, satellite clock drift, and ephemeris inaccuracies. The data is processed at master stations to generate correction messages, which are then uplinked to geostationary satellites (GEO satellites) for broadcast to user equipment over the same frequency band as GPS. The UE receives both the standard GPS signals and the WAAS correction messages, applying the corrections in real-time to compute a more precise position. Architecturally, WAAS integration in 3GPP involves the UE's positioning capabilities, where the UE may report its ability to use WAAS (or other SBAS) in positioning protocols like LTE Positioning Protocol (LPP) or NR Positioning Protocol (NRPP). The network can request or assist in WAAS-aided positioning for services such as emergency call location (E911) or commercial location-based services. Key components include the WAAS GEO satellites, ground uplink stations, and the UE's GNSS receiver with SBAS support. Its role is to provide enhanced positioning performance meeting requirements for safety-of-life applications, which demand high integrity, accuracy, and availability beyond what standalone GPS offers.
Purpose & Motivation
WAAS was created to address the limitations of standalone GPS, which lacks sufficient accuracy, integrity, and availability for critical applications, especially in aviation. GPS alone can have errors of several meters, and it does not provide timely warnings when the system is unreliable. WAAS solves these problems by providing differential corrections and integrity monitoring, reducing position errors to less than one meter horizontally and vertically. This enables precision approaches in aviation without requiring ground-based navigation aids. In the 3GPP context, supporting WAAS allows mobile networks to leverage this enhanced positioning capability for emergency services, where accurate location can be life-saving, and for advanced location-based services that require higher precision. The integration into 3GPP standards, beginning in Release 8, was motivated by regulatory requirements for enhanced emergency caller location and the growing demand for precise positioning in various commercial and safety applications, bridging the gap between telecommunications and satellite navigation systems.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (29 CRs across 4 releases). Complements the general historical overview above with the evidence-based evolution of this function.
Studied in Rel-8, normative work from Rel-16.
In Release 16, the WAAS function was enhanced primarily through updates to the A-GNSS specifications for the BeiDou Satellite System (BDS). Specifically, support was introduced for the new B1C signal and the B1I signal ICD file was updated to version 3.0. Furthermore, the release added support for GNSS Integer Ambiguity Level Indications and included clarifications to the meaning of GNSS terms within the positioning protocols.
- Introduction of B1C signal in BDS system in A-GNSS TS 36.305CR0083
- Introduction of B1C signal in BDS system in A-GNSS TS 37.355CR0248
- Introducing support for GNSS Integer Ambiguity Level Indications TS 37.355CR0252
- Introduction of B1C signal in BDS system in A-GNSS TS 38.305CR0013
- Update B1I signal ICD file to v3.0 in BDS system in A-GNSS TS 36.305CR0088
- Update B1I signal ICD file to v3.0 in BDS system in A-GNSS TS 37.355CR0259
+ 3 more changes
In Release 17, the WAAS function was enhanced with new capabilities for the BDS (BeiDou) system, specifically introducing support for the B2a and B3I signals and GNSS positioning integrity. The release also included clarifications and corrections to high-accuracy GNSS data, such as the provision of NMEA GGA sentence information in location estimates and updates to the definitions for SSR orbit, clock, and URA fields to align with RTCM standards.
- Introduction of B2a and B3I signal in BDS system and GNSS Positioning Integrity TS 36.305CR0107
- NMEA GGA sentence info in high accuracy GNSS location estimates [HA-GNSS-NMEA] TS 37.355CR0349
- Correction on the GNSS Orbit and Clock Integrity Bounds in TS 37.355 TS 37.355CR0377
- GNSS SSR BDS orbit emphemeris reference clarification to align with RTCM TS 37.355CR0461
- Field description correction for HA-GNSS metrics TS 37.355CR0474
- Correcting field description and definition of GNSS-SSR-URA TS 37.355CR0400
+ 2 more changes
In Release 18, the WAAS function was enhanced with new assistance information for identifying GNSS Line-of-Sight (LOS) and Non-Line-of-Sight (NLOS) conditions. The release also included corrections and clarifications for A-GNSS positioning, specifically regarding the support of GNSS-Almanac and GNSS UTC-Model, and made corrections to information elements for the NavIC almanac and related field descriptions.
- GNSS LOS/NLOS assistance information [GNSS LOS/NLOS] TS 37.355CR0446
- Miscellaneous RIL corrections for GNSS LOS/NLOS [GNSS LOS/NLOS] TS 37.355CR0495
- Correction on GNSS-AlmanacSupport and GNSS-UTC-ModelSupport in A-GNSS positioning TS 37.355CR0518
- Correction on NavIC almanac set IE, and field descriptions under KlobucharModelParamater and GNSS-SystemTime. TS 37.355CR0534
In Release 19, the WAAS function was enhanced through the introduction of support for new global navigation satellite system signals within the A-GNSS framework. Specifically, this included the integration of the NavIC L1 SPS and the BDS B2b signals into the relevant LTE, NR, and LPP stage 2 specifications. The release also introduced a new UE capability to request equalIntegerAmbiguityLevel assistance data and included miscellaneous corrections for LPP.
- Introduction of NavIC L1 SPS A-GNSS in LTE Stage 2 specification TS 36.305CR0120
- Introduction of BDS B2b in A-GNSS TS 36.305CR0121
- Introduction of NavIC L1 SPS A-GNSS in LPP TS 37.355CR0532
- Introduction of B2b signal in BDS system in A-GNSS TS 37.355CR0545
- UE request for equalIntegerAmbiguityLevel assistance data [GNSS-EqualIntegerAmbiguity] TS 37.355CR0557
- Introduction of NavIC L1 SPS A-GNSS in NR Stage 2 specification TS 38.305CR0179
+ 2 more changes
Explore further
Broader topics and technologies where WAAS plays a role.
Defining Specifications
3GPP specifications that define or reference WAAS, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TR 21.905 vj00 | 3GPP Technical Terms and Definitions | Rel-19 |
| TS 22.071 vj00 | 3GPP TS 22.071: Location Services (LCS) Stage 1 | Rel-19 |
| TS 25.305 vj00 | UTRAN UE Positioning Stage 2 | Rel-19 |
| TS 25.331 vj00 | UTRAN RRC Protocol Specification | Rel-19 |
| TS 25.423 vj00 | UTRAN RNSAP Specification | Rel-19 |
| TS 25.433 vj00 | Node B Application Part (NBAP) Protocol | Rel-19 |
| TS 25.453 vj00 | PCAP Protocol Specification | Rel-19 |
| TS 36.305 vj00 | UE Positioning in E-UTRAN Stage 2 | Rel-19 |
| TS 36.355 vj00 | LTE Positioning Protocol (LPP) | Rel-19 |
| TS 37.355 vj20 | LTE Positioning Protocol (LPP) | Rel-19 |
| TS 37.571 vj00 | UE Conformance for Positioning | Rel-19 |
| TS 38.305 vj00 | NG-RAN UE Positioning Stage 2 | Rel-19 |
| TS 38.455 vj10 | NR Positioning Protocol A (NRPPa) | Rel-19 |
| TS 44.031 vj00 | Radio Resource LCS Protocol (RRLP) | Rel-19 |