Description
The Location Services User Plane Protocol (LCS-UPP) is the specific protocol that realizes the LCS User Plane (LCS-UP) framework. It is an application-layer protocol that rides on top of the standard 5G user plane transport stack (IP, UDP, GTP-U). LCS-UPP defines the structure of Protocol Data Units (PDUs) that carry all positioning-related information exchanged directly over the data channel, enabling efficient, high-volume transfers that would be prohibitive over control plane signaling.
Technically, LCS-UPP PDUs encapsulate payloads from higher-layer positioning protocols. The most significant of these is the LTE Positioning Protocol (LPP), which is repurposed for 5G. In the LCS-UP context, LPP messages (which contain measurement requests, measurement reports, assistance data delivery, and location information) are not sent over NAS but are instead packaged as the payload within an LCS-UPP PDU. The LCS-UPP layer adds its own header, which includes control information such as a PDU Type (e.g., Data, Acknowledge), a Sequence Number for reliable delivery if needed, and identifiers to associate the PDU with a specific positioning session or transaction. This encapsulated LPP-in-LCS-UPP PDU is then sent over the established PDU Session's user plane bearer.
The protocol operates between two primary endpoints: the LCS-UPP layer in the UE and the LCS-UPP layer in the Location Management Function (LMF). The gNB and UPF are transparent to the LCS-UPP content; they merely forward the IP packets containing the GTP-U-encapsulated LCS-UPP PDUs. LCS-UPP supports both connection-oriented and connectionless modes. For a sustained positioning session with frequent data exchange (e.g., continuous tracking), a connection-oriented context can be established, managing sequence numbers and acknowledgments. For one-off assistance data delivery, a simple connectionless datagram can be used. The protocol is designed to be lightweight, minimizing overhead to preserve the low-latency advantage of the user plane. It works in concert with control plane protocols (like LPP over NAS) which are still used for session establishment, capability negotiation, and activation/deactivation of the user plane positioning data transfer.
Purpose & Motivation
LCS-UPP was developed to provide a standardized, efficient encapsulation and delivery mechanism for positioning protocol data over the 5G user plane. Before its introduction, positioning protocols like LPP were solely carried over the control plane (NAS), which was not designed for the data intensity of advanced positioning. The need for a user plane protocol became apparent with 5G-Advanced use cases requiring the transfer of large assistance data files (e.g., real-time kinematic (RTK) corrections, precise point positioning (PPP) data) and high-frequency streams of raw sensor measurements from the UE.
The protocol solves the problem of how to reliably and efficiently transport structured positioning messages within the unstructured flow of user plane IP packets. It provides the necessary session management, message framing, and optional reliability mechanisms at the application layer without relying on TCP, which may introduce unacceptable latency and jitter. By defining LCS-UPP, 3GPP created a purpose-built conduit that allows the rich feature set of LPP (and future positioning protocols) to be leveraged in a high-performance data plane context. This enables network operators and service providers to offer differentiated, high-accuracy positioning-as-a-service with guaranteed QoS, a key enabler for monetizing 5G network capabilities in vertical markets.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (250 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the LCS-UPP (Location Services User Plane Protocol) was newly introduced as a dedicated user-plane solution for location services, as defined in TS 24.572. This protocol provides the specific procedures and formats for transporting location-related data directly over the user plane, separate from the control plane signaling used in earlier releases. Its introduction enables more efficient and scalable positioning for 5G devices.
- NW slicing and delayed re-registration due to emergency services TS 24.501CR0124
- NW slicing and delayed registration due to emergency services, reject PDU session request TS 24.501CR0290
- Correction for establishment of user-plane resources TS 24.501CR0013
- Exchange of extended protocol configuration options TS 24.501CR0023
- UAC information and establishment cause when uplink user data packet is to be sent for a PDU session with suspended user-plane resources TS 24.501CR0027
- Authentication for normal services not accepted by network TS 24.501CR0035
+ 12 more changes
In Release 16, the LCS-UPP (Location Services User Plane Protocol) was enhanced to support a deferred Mobile-Terminated Location Request (5GC-MT-LR) via NAS transport, allowing supplementary services messages to carry the location service request. Furthermore, the protocol introduced the capability to transfer Ciphering Key Information for Broadcast Location Assistance Data to the UE. These additions provided new mechanisms for delivering location services and security material through both control plane and user plane pathways.
- User plane CIoT 5GS optimization TS 24.501CR1130
- Idle mode optimizations for 5G Control plane CIoT small data transfer t TS 24.501CR1311
- Header compression for control plane user datat TS 24.501CR1318
- Addition of location service message condition to Additional informaton IE TS 24.501CR1336
- NAS transport of supplementary services messages for a deferred 5GC-MT-LR TS 24.501CR1365
- Port management information container: Delivery via the NAS protocol and coding TS 24.501CR1470
+ 41 more changes
In Release 17, the LCS-UPP (User Plane Location Services) protocol was introduced as a new Stage 3 specification, TS 24.572, to define the user plane procedures for location services. This addition complements the existing stage 2 architectural work on LCS and provides the detailed protocol handling for location-based applications. The specification works alongside other Release 17 enhancements for positioning, such as those for sidelink and ranging-based services.
- Network shall not release the RRC connection for ProSe services TS 24.501CR3126
- UE's handling of the indication of country of UE location TS 24.501CR3219
- Deregister for disaster inbound roaming services TS 24.501CR3512
- Using Service Request procedure for removing paging restrictions in 5GS for MUSIM UE that uses the control plane CIoT 5GS optimization TS 24.501CR3439
- 5GMM procedures for satellite access for reject cause on UE location - alternative handling TS 24.501CR3217
- PDU session establishment request for UAS services TS 24.501CR3418
+ 47 more changes
In Release 18, the LCS-UPP (Location Services User Plane Protocol) introduced new support indications and capability signaling for user plane positioning. Specifically, enhancements included a user plane positioning capability indication and updates to UL/DL NAS transport procedures to facilitate this functionality. These additions expanded the protocol's ability to signal and manage positioning resources over the user plane.
- User plane positioning capability indication TS 24.501CR5015
- Support for UE accessing SNPN services using non-3GPP access TS 24.501CR4944
- Protocol error handling enhancements for Type 6 IE container IEs TS 24.501CR5031
- The enhancement on onboarding services in SNPN supporting localized services TS 24.501CR5087
- CH controlled prioritized list of preferred SNPNs and GINs for access for localized services in SNPN TS 24.501CR5036
- User plane positioning capability TS 24.501CR5285
+ 92 more changes
In Release 19, key enhancements for the LCS-UPP function included the introduction of network capability and UE indication support for multiple LCS secured user plane connections per UE. It also specified the use of routing information to map the user plane connection in the UE and to support LMF relocation on a new user plane connection. Furthermore, corrections and updates were made to procedures and messages, including the DL LCS-UP TRANSPORT message and the establishment of a specific TCP port number for LCS-UPP.
- Information for ensuring appropriate cell reselection for localized services in SNPN TS 24.501CR6486
- Handling of regulatory prioritized services in non-allowed area TS 24.501CR6332
- NW capability for multiple LCS-UPP connections per UE TS 24.501CR6953
- Use routing information to map the user plane connection in the UE TS 24.572CR0115
- Include routing information for LMF relocation on new user plane connection TS 24.572CR0116
- Support of Location Service Involving WAB-Nodes TS 38.305CR0196
+ 28 more changes
Explore further
Broader topics and technologies where LCS-UPP plays a role.
Defining Specifications
3GPP specifications that define or reference LCS-UPP, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 24.501 vj50 | 5G NAS Protocols Specification | Rel-19 |
| TS 24.572 vj50 | 5G LCS User Plane Protocol Specification | Rel-19 |
| TS 38.305 vj00 | NG-RAN UE Positioning Stage 2 | Rel-19 |