Description
The UTRAN Position Signal Measurement Function (U-PSMF) is a critical component within the UTRAN architecture dedicated to facilitating positioning services. It operates as a logical function, typically residing within the Radio Network Controller (RNC), responsible for the collection, processing, and reporting of radio signal measurements necessary for determining the location of User Equipment (UE). The U-PSMF interfaces with other network elements, such as the Serving Mobile Location Centre (SMLC) in the core network, to support various positioning methods mandated by 3GPP standards.
The primary operational role of the U-PSMF involves orchestrating the measurement process. Upon receiving a positioning request, often triggered by a location-based service application, the U-PSMF instructs the relevant Node Bs and the target UE to perform specific signal measurements. These measurements can include parameters like the Round Trip Time (RTT), observed time differences, or signal strengths. The U-PSMF aggregates this raw measurement data from multiple sources within the radio access network.
After collection, the U-PSMF processes these measurements. This processing may involve filtering, time-stamping, and formatting the data according to the requirements of the chosen positioning method, such as Observed Time Difference of Arrival (OTDOA) or Uplink Time Difference of Arrival (U-TDOA). The processed measurement report is then forwarded to the SMLC. The SMLC, which contains the positioning calculation algorithms, uses this report to compute the UE's estimated geographical coordinates. The U-PSMF thus acts as the RAN's agent for positioning, abstracting the complexity of radio measurement collection from the core network's location server.
Purpose & Motivation
The U-PSMF was introduced to standardize and centralize the signal measurement collection process for UE positioning within UTRAN. Prior to its formal definition, positioning capabilities were less structured and often vendor-specific, hindering interoperability and the reliable deployment of location-based services (LBS). The creation of the U-PSMF addressed the growing regulatory and commercial demand for accurate mobile location, driven by requirements like Enhanced 911 (E911) in the United States and the burgeoning market for location-aware applications.
Its purpose is to solve the problem of efficiently and reliably gathering the precise radio measurements needed for network-based and UE-assisted positioning techniques. By defining a dedicated functional entity within the RNC, 3GPP ensured a consistent interface (e.g., to the SMLC via the Lup interface) and a controlled process for measurement coordination. This separation of concerns allows the core network's SMLC to focus on location calculation algorithms while the U-PSMF handles the real-time, radio-specific task of measurement management, improving overall system reliability and performance for positioning requests.
Key Features
- Coordinates radio signal measurements for UE positioning within UTRAN
- Interfaces with the Serving Mobile Location Centre (SMLC) in the core network
- Collects and processes measurements like Round Trip Time (RTT) and observed time differences
- Supports multiple 3GPP positioning methods including OTDOA and Cell-ID
- Resides as a logical function typically within the Radio Network Controller (RNC)
- Formats and delivers measurement reports for location calculation
Evolution Across Releases
Initially introduced as part of the UTRAN positioning architecture. The U-PSMF was defined as the standardized function within the RNC responsible for managing all positioning-related signal measurements, establishing the foundational procedures for interaction with the SMLC and control over UE and Node B measurement tasks.
Defining Specifications
| Specification | Title |
|---|---|
| TS 25.305 | 3GPP TS 25.305 |