Sign in Subscribe

Describe the purpose of the Mobile Station Roaming Number (MSRN).

Last updated on 


The Mobile Station Roaming Number (MSRN) is a critical parameter in GSM (Global System for Mobile Communications) networks, and it serves a specific purpose in call routing during the process of establishing a mobile-to-mobile or mobile-to-landline connection. The MSRN is dynamically assigned to a mobile station (MS) during the call setup procedure and is used to route the call to the correct destination. Here's a detailed technical explanation of the purpose of the Mobile Station Roaming Number:

  1. Call Setup Procedure:
    • When a mobile user initiates a call, the network must determine the appropriate destination for the call. This involves identifying the current location of the called mobile station.
  2. Mobile Subscriber Roaming:
    • Mobile subscribers may roam outside their home network's coverage area. In such cases, the call may need to be routed to the subscriber's current location, which could be in a different network.
  3. HLR and VLR Interaction:
    • The Home Location Register (HLR) is the central database that stores subscriber information, including the subscriber's current location area and the Visitor Location Register (VLR) associated with that location area.
    • The VLR is a temporary database that stores subscriber information within the current location area.
  4. Assignment of MSRN:
    • When a call is initiated to a mobile subscriber, the HLR queries the VLR associated with the subscriber's current location.
    • The VLR then assigns a Mobile Station Roaming Number (MSRN) to the subscriber for the duration of the call setup procedure.
  5. MSRN Format:
    • The MSRN is a temporary number assigned to the subscriber, and it has a specific format.
    • It typically includes information about the MSC (Mobile Switching Center) and the subscriber's unique identifier within the MSC.
  6. Temporary Routing Information:
    • The MSRN serves as temporary routing information for the call. It indicates to the originating MSC how to route the call to the current location of the mobile subscriber.
  7. Routing to the VLR:
    • The MSRN is used by the originating MSC to route the call to the MSC associated with the subscriber's current location (VLR).
    • This ensures that the call is directed to the correct VLR handling the subscriber's current location area.
  8. Subscriber Identification:
    • The MSRN is also used to identify the specific mobile subscriber within the VLR.
    • It helps the VLR retrieve the necessary subscriber information for call processing.
  9. Dynamic Assignment:
    • The MSRN is dynamically assigned for each call setup procedure. Once the call is completed, the MSRN is released and can be reused for other call setup procedures.
  10. Subscriber Mobility:
    • As mobile subscribers move between different location areas, the MSRN is assigned dynamically to reflect the current location of the subscriber.
    • This supports subscriber mobility and ensures that calls are efficiently routed to the correct location.
  11. Efficient Call Routing:
    • The use of the MSRN allows for efficient call routing, especially in scenarios where the called subscriber is roaming outside their home network.
    • It enables the network to adapt to the subscriber's current location and route the call accordingly.
  12. Temporary Nature:
    • The MSRN is temporary and associated with the duration of the call setup process. Once the call is established, the MSRN is released.
  13. Enhanced Security:
    • The use of the MSRN adds a layer of security by providing temporary and dynamically assigned routing information.
    • This dynamic assignment reduces the risk of intercepting and tracking calls based on a static identifier.

In summary, the Mobile Station Roaming Number (MSRN) in GSM networks serves the purpose of providing temporary routing information during the call setup process. It facilitates efficient call routing to the current location of a mobile subscriber, especially when the subscriber is roaming outside their home network. The MSRN ensures that calls are directed to the appropriate Visitor Location Register (VLR) handling the subscriber's current location area, supporting subscriber mobility and optimizing call routing within the GSM network.