What is MT-LR Mobile Terminating Location Request

Technical details of the Mobile Terminating Location Request (MT-LR) in mobile telecommunications systems. MT-LR plays a crucial role in determining the location of a mobile device when it receives incoming calls or messages. Here’s an in-depth exploration of MT-LR:

1. Overview and Significance:
   • MT-LR is an essential signaling procedure used in Global System for Mobile Communications (GSM), Universal Mobile Telecommunications System (UMTS), and Long-Term Evolution (LTE) networks.
   • Its primary purpose is to provide accurate location data to the network, enabling a range of location-based services.
   • MT-LR is particularly critical for emergency services like Enhanced 911 (E911), where precise location information is vital for effective response to distress calls.
   • Additionally, MT-LR supports services such as mobile advertising, location-based notifications, asset tracking, and fleet management.
2. Entities Involved:
   • Mobile Switching Center (MSC): The MSC responsible for handling the call receives the MT-LR request.
   • Home Location Register (HLR): A central database storing subscriber-related information, including the current Visitor Location Register (VLR) location of the mobile device.
   • Visitor Location Register (VLR): Determines the current location area of the mobile subscriber within its coverage area.
   • Mobile Equipment (ME): Represents the mobile device itself.
3. MT-LR Procedure:
   • When an incoming call or message is directed towards a mobile subscriber:
     • The MSC requests location information from the HLR.
     • The HLR checks if the VLR location of the subscriber is available:
       • If available, it responds to the MSC with the corresponding VLR address.
       • If not available, the HLR requests the VLR to initiate a Location Area Update (LAU) procedure.
     • The VLR:
       • Determines the current location area of the mobile subscriber.
       • Retrieves location information from its internal database if the mobile device is registered with it.
       • If the location information is not available, it initiates a Location Area Update (LAU) to update the location in its database.
       • Ensures that subsequent MT-LR requests can be resolved efficiently.
4. Use Cases:
   • Emergency Services (E911): Accurate location data helps emergency responders reach the caller promptly.
   • Mobile Advertising: Targeted ads based on the user’s location.
   • Asset Tracking: Monitoring the location of valuable assets.
   • Fleet Management: Efficiently managing vehicle fleets based on real-time location.