How does a GMLC measure the location of mobile devices?

Published on: 08/04/2022
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A Gateway Mobile Location Centre is a platform that locates any mobile device at any time, without the need for an internet connection or an app download provided the mobile device is connected to its mobile carrier. 

By acquiring mobile devices’ locations, it enables Location-Based Services (LBS), including emergency services, vehicle tracking, location-based advertising, and much more. In the case of emergency calls, for example, the Location Retrieval Function (LRF) fused with a GMLC obtains the location information of the user who has started an emergency session. The Emergency Call Session Control Function (E-CSCF) receives the allocated outgoing address from the Routing Determination Function (RDF, collocated in Intersec GMLC/LRF) to route the emergency request to a Public Safety Answering Point (PSAP).


SMLC/SAS/e-SMLC/LMF on the other hand is a network element in the LCS network of a PLMN. It manages the overall coordination, calculation, and scheduling of resources required to determine the geographical location of an MS in the network.GMLC can be integrated with Serving Mobile Location Centres (SMLCs) to greatly increase the precision of location reporting.

How GMLC works

The GMLC interfaces with the Location Services (LCS) clients, which may be located outside of the network, such as a third-party VAS application. Individual requests to locate and report the geographic location of a user's mobile is received by the GMLC. Simultaneously, checks are done to ensure that the LCS client is permitted to make such a request and that the UE (User Equipment) can support LCS requests. GMLC is always installed on at least two servers, guaranteeing that the system is constantly up and running. It is also linked to the operator's monitoring system to ensure that maintenance runs smoothly. GMLC offers the operator detailed information on all system events, making issue discovery and resolution much easier.

Privacy is critical

To ensure privacy and respect for permission requirements, the Intersec GMLC solution executes verification and approval checks for all location requests from the LCS. The GMLC must figure out the serving node (MSC, MME, AMF...) in charge of the UE at the time of the LCS request. To do so, in standard call-flows GMLC sends a request to HLR/HSS/UDM to identify the current serving node. The HLR/HSS/UDM returns this data, and the GMLC sends a message to the appropriate serving node to get the subscriber location information.

Because Intersec has a far more advanced GMLC integrated into our real-time location platform, the standard approaches can be improved to facilitate any network integration or to enable unplanned use cases.

The essential functionality for Cell ID and Antenna Sector Positioning is included in GMLC. It can be implemented without any additional network features in any 2G/3G/4G/5G network.

Active - or on-demand - positioning

GMLC is used for active mobile positioning, meaning that it triggers specific activities on the network to retrieve a subscriber’s location in real-time. For improved positioning precision, a GMLC can connect with additional precise location components in the network. They are called differently depending on the network generation - SMLC (2G), SAS (3G), E-SMLC (4G), LMF (5G) -, and they oversee querying a set of data to the UE (User Equipment) and computing a precise location estimate with it.

The fundamental functionality of GMLC is to report a CSP's subscriber's current location information to preset endpoints. The subscriber's Cell ID and status are included in this data. Because it supports both SS7/Sigtran, Diameter, and HTTP/2 protocols, it can be used on 2G, 3G, 4G/LTE, and 5G networks. Also, it uses the Open Mobile Alliance (OMA) industry-standard mobile location protocol (MLP) to report the subscriber’s location to the predefined endpoints/applications.

Our solution simplifies the process of getting started with new technology and outlines the benefits a GMLC can bring to businesses. We specialize in all things data, bringing technologies that seamlessly fit in with existing systems and which will give the best return on your investment. In addition to the GMLC, we have passive location and all the panoply of precise geolocation, both in the control plane and in the user plane (SMLC/SAS/E-SMLC and LMF and passive E-CID). We developed the 2 together which unlocks a lot of features that permit the platform to make sense of its data. The Intersec off-the-shelf app suite is turnkey in deriving value from day one, its API and app builder fully Integrates with existing apps or helps to develop new ones while unlocking monetization opportunities with existing use cases. A gateway mobile location centre opens so many new opportunities to businesses, helping them stay relevant and innovative in an ever increasingly competitive world.

Regardless of your industry, GMLC is a worthwhile investment.


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