Technical details of the Mobile Station Roaming Number (MSRN) in GSM networks.
- Definition:
- The MSRN stands for Mobile Station Roaming Number.
- It is an E.164-defined telephone number used within mobile networks.
- The primary purpose of the MSRN is to route telephone calls from a GMSC (Gateway Mobile Switching Centre) to the target MAC id (Mobile Application Context identifier) associated with the called mobile subscriber.
- Function and Usage:
- When an incoming call is made to a roaming subscriber (someone who is currently outside their home network), the GMSC queries the Home Location Register (HLR) to obtain the MSRN.
- The HLR provides the GMSC with the temporary MSRN assigned to the roaming subscriber.
- The GMSC then uses this MSRN to route the call to the appropriate Visitor Location Register (VLR), which is responsible for managing the subscriber’s current location within the visited network.
- The VLR further forwards the call to the Mobile Switching Centre (MSC) serving the subscriber’s current location.
- Temporary Assignment:
- The MSRN is temporarily assigned to the mobile subscriber for the duration of the call.
- It acts as a directory number specific to that call.
- The MSRN ensures that the call is efficiently routed to the subscriber’s current location, even if the terminating MSC resides on a different switch from the originating MSC.
- This flexibility is essential because the MSC and VLR may not always be integrated into the same switch; they are considered separate nodes with their own routing addresses.
- SRI Response Message:
- The MSRN is one of the parameters returned in the Send Routing Information (SRI) Response message.
- In particular, the MSRN plays a crucial role in Mobile Number Portability (MNP) scenarios, where a subscriber has switched networks while retaining their original mobile number.
- In such cases, the MSRN can be modified as ‘RgN + MSISDN’ (where RgN represents the routing number and MSISDN is the mobile subscriber’s phone number).
