Description
Real-Time Kinematic (RTK) is an advanced positioning method standardized within 3GPP, particularly in specifications like TS 36.305 (LTE), TS 37.355 (LTE/NR), TS 38.305 (NR), and TS 38.859. It operates by comparing the phase of the carrier wave from Global Navigation Satellite System (GNSS) signals received at a rover (e.g., a UE) with those received at a fixed, known-location reference station. This differential approach cancels out common errors such as satellite clock drift, atmospheric delays, and orbital inaccuracies, enabling positioning accuracy at the centimeter level in real-time.
The architecture for RTK in 3GPP systems involves several key components: the UE (rover) equipped with a GNSS receiver capable of carrier-phase tracking, one or more reference stations with precisely known coordinates, and a communication link—typically provided by the mobile network (LTE or 5G NR)—to deliver correction data. The reference station calculates error corrections by comparing its known position with the measured GNSS data. These corrections, often formatted using standards like RTCM (Radio Technical Commission for Maritime Services) or 3GPP-defined protocols, are then transmitted to the UE via point-to-point or broadcast methods. The UE applies these corrections to its own GNSS measurements to compute a highly accurate position.
How RTK works involves the UE performing carrier-phase ambiguity resolution, a process of determining the integer number of wavelengths between the satellite and receiver. Once resolved, the carrier-phase measurements provide extremely precise range information. The 3GPP standards define protocols for delivering correction data, such as the LTE Positioning Protocol (LPP) and NR Positioning Protocol (NRPP), which support RTK as a high-accuracy method. The network can assist the UE by providing auxiliary data like approximate location, satellite ephemerides, and atmospheric models to speed up ambiguity resolution and improve reliability. RTK's role is integral to 5G's support for ultra-reliable low-latency communication (URLLC) and massive machine-type communication (mMTC), enabling precise positioning for critical applications.
Purpose & Motivation
RTK was integrated into 3GPP standards to meet the escalating demand for high-precision positioning in commercial and industrial applications. Traditional GNSS methods, such as standard GPS or Assisted-GPS (A-GPS), offer meter-level accuracy, which is insufficient for emerging use cases like autonomous driving, precision agriculture, drone navigation, and augmented reality. These applications require centimeter-level accuracy to ensure safety, efficiency, and functionality. The limitations of previous approaches included susceptibility to atmospheric errors, multipath interference, and the need for prolonged observation times to achieve high accuracy.
The motivation for its creation stems from the convergence of telecommunications and positioning technologies, leveraging mobile networks' ubiquitous coverage and low-latency connectivity to deliver RTK correction data reliably. Before 3GPP standardization, RTK systems often relied on dedicated radio links or internet connections, which were not optimized for mobility, scalability, or integration with cellular devices. By standardizing RTK support within LTE and 5G, 3GPP enables seamless, network-assisted high-accuracy positioning as a native service, reducing deployment costs and complexity.
Historically, RTK has been used in surveying and geodesy for decades, but its adoption in mass-market devices was hindered by the cost and complexity of receivers and correction data delivery. 3GPP's work, starting in Release 15 with 5G, addresses these barriers by defining efficient protocols and network architectures that support low-latency correction data transmission over cellular links. This solves the problem of providing real-time, high-accuracy positioning to a vast number of devices, unlocking new vertical markets and enhancing existing location-based services with unprecedented precision.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (31 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the Real-Time Kinematic (RTK) function was introduced, including the specification of RTK assistance data for network-assisted GNSS positioning. This new capability supports State Space Representation (SSR) corrections, which provide individual GNSS error source parameters to the UE, enabling high-precision positioning by correcting its own GNSS observations.
In Release 16, the key enhancement for the RTK function was the introduction of support for GNSS Integer Ambiguity Level Indications, which are critical for high-precision positioning. This release also updated assistance data for the BeiDou Navigation Satellite System (BDS), including the introduction of the B1C signal and updates to the B1I signal ICD file to version 3.0. These changes improved the support for State Space Representation (SSR) corrections, enabling more precise RTK positioning.
- 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 enhancements for RTK included the introduction of the BeiDou (BDS) B2a and B3I signals into the GNSS system support and the provision of GNSS Positioning Integrity. Furthermore, the release clarified and corrected several State Space Representation (SSR) fields and models, such as orbit and clock integrity bounds and tropospheric delay corrections, to improve the accuracy and alignment of high-accuracy GNSS location estimates.
- 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, enhancements for RTK primarily focused on refining assistance data for GNSS positioning, specifically by introducing support for GNSS Line-of-Sight (LOS) and Non-Line-of-Sight (NLOS) assistance information. This builds upon the existing framework for State Space Representation (SSR) corrections, which allow a UE to perform RTK positioning by correcting individual GNSS error sources. The release also included corrections to existing assistance data elements, such as those for almanac support and specific navigation system models like NavIC.
- 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 key enhancement for the RTK function was the introduction of a new UE request for `equalIntegerAmbiguityLevel` assistance data, which is a specific type of data facilitating high-accuracy positioning. Furthermore, the release expanded A-GNSS support by introducing assistance for the NavIC L1 SPS and BDS B2b signals across LTE, NR, and the LPP specification. These updates provided new GNSS system options and refined assistance data for network-assisted, carrier-phase-based positioning methods like RTK.
- 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 RTK plays a role.
Defining Specifications
3GPP specifications that define or reference RTK, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 36.305 vj00 | UE Positioning in E-UTRAN Stage 2 | Rel-19 |
| TS 37.355 vj20 | LTE Positioning Protocol (LPP) | Rel-19 |
| TS 38.305 vj00 | NG-RAN UE Positioning Stage 2 | Rel-19 |
| TR 38.859 vi10 | Technical Report | Rel-18 |