In GSM networks, the Mobile Station Roaming Number (MSRN) is a temporary telephone number used for routing calls to a mobile subscriber who is roaming. The MSRN is assigned to a mobile for every mobile terminated call, ensuring that the call is delivered to the correct location.
The format of an MSRN follows the E.164 numbering plan, which typically includes:
• Country Code (CC): Identifies the country of the network where the call is being routed.
• National Destination Code (NDC): Specifies the destination network or specific part of a national network.
• Subscriber Number (SN): The unique number assigned to the subscriber within the destination network.
The MSRN is used in the following way in GSM networks:
1. When a call is made to a roaming mobile station, the Home Location Register (HLR)is queried to locate the subscriber’s current network.
2. The HLR responds with an MSRN, which is temporarily assigned to the subscriber by the Visited Location Register (VLR) in the area where the subscriber is roaming.
3. The Gateway Mobile Switching Centre (GMSC) then uses the MSRN to route the call through the appropriate network elements to reach the roaming subscriber.
The MSRN is essential for ensuring that calls are correctly routed to mobile subscribers regardless of their location, providing seamless communication for users on the move.