Technical details of Mobile Terminated Roaming Forwarding (MTRF):
- Definition:
- MTRF is a technique used in Circuit-Switched Fallback (CSFB) scenarios within mobile networks.
- It aims to reduce the delay that may occur during an MT (Mobile Terminated) fallback situation.
- In an MT fallback scenario, a mobile phone transitions from a higher-speed data network (such as LTE) to a legacy 2G or 3G network due to various reasons (e.g., poor coverage, network handover, or location area mismatch).
- Scenario:
- Imagine a subscriber’s phone is roaming outside their home network coverage area.
- At the point of fallback (when the phone switches from LTE to 2G/3G), it attaches to a different Mobile Switching Center (MSC).
- This change of MSC can happen due to factors like Location Area mismatch.
- Purpose of MTRF:
- When an incoming voice call or SMS message arrives for the roaming subscriber, the network needs to route it to the correct MSC.
- MTRF ensures that the call or message is forwarded from the MSC attempting to handle it to the MSC that is actually responsible for the subscriber.
- By doing so, MTRF minimizes the delay and ensures seamless connectivity for the subscriber.
- Key Points:
- CSFB: MTRF is primarily used in CSFB scenarios, where LTE-capable phones fall back to legacy networks for voice calls.
- Subscriber Mobility: It addresses the mobility of subscribers while roaming.
- MSC Handover: The handover from one MSC to another triggers MTRF.
- Location Area Mismatch: If the subscriber’s location area changes during roaming, MTRF ensures proper call forwarding.
