MSC/VLR Subscriber Record Retention for Handover Call Continuity
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Solution Overview
Problem
In mobile communication networks, call dropping occurs when a subscriber moves between MSC/VLRs during call setup, as the old MSC/VLR loses the subscriber's profile and MSRN before the new MSC/VLR is registered, leading to failed call connections.
Innovation Solution
Retaining the subscriber record, including the MSRN, in an active state at the MSC/VLR for a predefined time after the subscriber leaves, allowing identification and handling of incoming calls, even if the subscriber has moved to a new MSC/VLR, and enabling call forwarding if necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the subscriber profile is deleted from the old MSC/VLR immediately after handover, then bandwidth consumption between HLR and MSC/VLR is reduced, but call connection reliability deteriorates due to call dropping
Solution Approach 1:
The patent applies preliminary action by retaining the subscriber profile and MSRN at the old MSC/VLR for a predefined time period before deletion. This ensures that if a call arrives during the handover transition period, the old MSC/VLR can still process and forward the call to the new MSC/VLR, preventing call dropping while minimizing bandwidth usage by not retaining profiles indefinitely
Solution Approach 2:
The patent uses the old MSC/VLR as an intermediary during the handover transition. By keeping the subscriber profile temporarily, the old MSC/VLR acts as a mediator that can receive incoming calls and forward them to the new MSC/VLR, ensuring call continuity. This intermediary role resolves the contradiction by maintaining call reliability during transition while allowing profile deletion after the transition period
2Reliability
If the subscriber profile is retained in inactive state at the old MSC/VLR, then call connection reliability is improved, but system complexity increases due to profile management overhead
Solution Approach 1:
The patent changes the state parameter of the subscriber profile from 'deleted' to 'retained for predefined time' at the old MSC/VLR. This parameter change enables the system to maintain call reliability by keeping profiles available during handover transition, while the predefined time limit prevents indefinite retention and associated complexity
3Reliability
If the entire subscriber profile is transmitted between HLR and MSC/VLR frequently, then call connection reliability is improved, but bandwidth consumption increases
Solution Approach 1:
The patent uses preliminary action by pre-retaining the subscriber profile at the old MSC/VLR before it would need to be re-transmitted from HLR. This prevents the need for frequent full profile transmissions between HLR and MSC/VLR, reducing bandwidth consumption while ensuring call reliability is maintained during handover transitions
Data Source
AI summary
Retaining contact data for a subscriber to a mobile communication network may be provided by a method and apparatus components therefor that allow for storing contact data for subscribers to a mobile network located within an area served by a mobile switching center, receiving confirmation at the mobile switching center (MSC) that a subscriber has left the area, updating the contact data to identify that the subscriber has left the area, and retaining at least part of the contact data, the retained part of the contact data containing call forwarding details for the subscriber.