4 General
25.1113GPPLocation Measurement Unit (LMU) performance specificationRelease 17TSUser Equipment (UE) positioning in UTRAN
4.1 Main concepts
The LMU is either located as a separate unit in an existing network or typically located at Node B or BTS sites. Therefore the LMU radio requirements assume that the isolation between the LMU and any other network to be protected is to be at least 30dB.
The communication link between LMU and Stand-Alone SMLC is not a radio interface over the air. Requirements in this document therefore do not cover the situation when the LMU is transmitting over the air on this interface between LMU and Stand-Alone SMLC.
4.2 LMU Classes
The requirements in this specification apply to Wide Area LMUs and Medium Range LMUs.
Wide Area LMUs are characterised by requirements derived from Macro Cell scenarios with an LMU to UE minimum coupling loss equal to 70 dB.
Medium Range LMUs are characterised by requirements derived from Micro Cell scenarios with an LMU to UE minimum coupling loss equal to 53 dB.
For Pico Cell scenarios, the location of the BS provides sufficient accuracy; therefore, a Local Area LMUs class is not specified.
4.3 U-TDOA architecture
A sample architecture is shown in Figure 3.1 depicting the LMU’s relationship with other network elements. The LMU is typically located at the Node B. The LMUs communicate with the SMLC that distributes UTDOA reference data from the reference LMU to other cooperating LMUs when performing UE positioning.
Figure 3.1: Example of UTDOA deployment