2. Architecture

2.1 Control-Plane LCS Architecture (GSM/UMTS/LTE)

In control-plane positioning, the location is obtained via signaling in the core network (as opposed to the user’s device directly sending GPS info). The GMLC is central to the LCS server function in the core network, interacting with other core nodes responsible for subscriber mobility and positioning. Key network elements and interfaces in a 2G/3G/LTE LCS architecture are as follows:
GMLC (Gateway Mobile Location Centre): The LCS server node that interfaces with external clients (Le) and with core network nodes. It performs authorization, privacy checking, and forwards positioning requests to the serving network. In one PLMN there may be multiple GMLCs for load-sharing or regional deployment. The GMLC maintains interfaces Lg/Lgd to request location from MSC/VLR or SGSN (for CS or PS domains) and SLg to request location from the MME in EPS. It also uses Lh/SLh to get subscriber routing data from HLR/HSS. If inter-GMLC communication is needed (roaming scenario), the GMLC uses Lr to communicate with a peer GMLC in another network.

HLR/HSS