Hello Experts.
How LMF retrieve UE positioning?
Admin note: this post was updated with image below.
The new entity, location management function (LMF), is central in the 5G positioning architecture.
The LMF receives measurements and assistance information from the next generation radio access network (NG-RAN) and the mobile device, otherwise known as the user equipment (UE), via the access and mobility management function (AMF) over the NLs interface to compute the position of the UE.
Due to the new next generation interface between the NG-RAN and the core network, a new NR positioning protocol A (NRPPa) protocol was introduced to carry the positioning information between NG-RAN and LMF over the next generation control plane interface (NG-C).
These additions in the 5G architecture provide the framework for positioning in 5G. The LMF configures the UE using the LTE positioning protocol (LPP) via AMF.
The NG RAN configures the UE using radio resource control (RRC) protocol over LTE-Uu and NR-Uu.
You can continue reading in this article: https://www.ericsson.com/en/blog/2020/12/5g-positioning--what-you-need-to-know#:~:text=The%20new%20entity%2C%20location%20management%20function%20(LMF)%2C%20is%20central%20in%20the%205G%20positioning%20architecture
5G positioning: What you need to know
The arrival of 5G delivers new enhanced parameters for positioning accuracy down to the meter, decimeter and centimeter. In this technical overview, we break down the accuracy requirements of emerging 5G use cases and explore the key features of new 3GPP 5G positioning architecture. Learn more below.
It’s clear from 38.305 that the LMF communicates with the serving gNB directly using the AMF as a transparent channel.
My question is, how does the LMF determines who is the serving gNB for a given UE? and how it is notified when a UE moves to another gNB?
It’s in fact using NRPPa payload over n2 interface through the AMF.