User Plane Positioning Connection Management Information

Description

User Plane Positioning Connection Management Information (UPP-CMI) is a Rel-19 concept that defines the structured information used to manage user-plane positioning connections. While UPP-CM describes the overall management framework, UPP-CMI specifies the actual data elements, parameters, and state variables that are exchanged between the UE and the network to establish, maintain, and release a user-plane positioning session. It is specified in 24.501 (Non-Access Stratum protocols) and 24.572 (User Plane Positioning protocols).

UPP-CMI encompasses several categories of information. First, it includes connection identifiers that uniquely associate a positioning session with a user-plane bearer or PDU session. Second, it contains configuration parameters such as the positioning methods to be used, the requested accuracy and latency, and the reporting mode (periodic, event-triggered, or on-demand). Third, it includes state information that reflects the current status of the connection, such as active, suspended, or released. Fourth, it may include security-related parameters to ensure that positioning data is protected and that only authorized entities can access location information.

The information is exchanged during session establishment and modification procedures. For example, when the UE requests a user-plane positioning session, it sends a request that includes UPP-CMI elements specifying its capabilities and requirements. The network (typically the LMF or a dedicated positioning server) responds with UPP-CMI that confirms the session parameters and provides any necessary assistance data. During the session, UPP-CMI may be updated to reflect changes in requirements or network conditions. Upon termination, UPP-CMI is used to release resources and clean up state.

In the NAS layer (24.501), UPP-CMI may be carried in specific NAS messages or as part of a container that is transparent to the AMF. In the user-plane positioning protocol (24.572), UPP-CMI is encoded in protocol data units that are transported over the user plane. The exact encoding and structure are defined in the specifications, ensuring interoperability between different vendors' equipment.

UPP-CMI is important because it provides the necessary control and configuration data for user-plane positioning to function. Without a well-defined set of information elements, the UE and network could not coordinate positioning sessions effectively. It also enables flexibility, allowing different positioning methods and QoS levels to be supported within the same framework. As 5G-Advanced evolves, UPP-CMI will likely be extended to support new positioning techniques and services.

Purpose & Motivation

UPP-CMI was created to provide a standardized way to convey the management information required for user-plane positioning connections. In the absence of such a definition, each implementation might use proprietary parameters, leading to interoperability issues. By specifying UPP-CMI in 3GPP specifications, the industry ensures that UEs and network equipment from different vendors can work together seamlessly.

The need for UPP-CMI arises from the complexity of managing positioning sessions over the user plane. Unlike control-plane positioning, where signaling is relatively simple and infrequent, user-plane positioning may involve continuous data flows and dynamic adjustments. UPP-CMI provides the means to negotiate and update session parameters, monitor connection status, and handle error conditions. It also supports the integration of positioning with other user-plane services, such as data and voice, by allowing the network to allocate resources appropriately.

Historically, positioning information in 3GPP was primarily carried in control-plane protocols like LPP. UPP-CMI represents a shift towards a more data-centric approach, aligning with the overall 5G trend of user-plane optimization. It addresses the limitations of control-plane signaling by enabling richer, more dynamic management of positioning connections.