MSC Paging via Alternative MME Pool for CSFB Call Reliability
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Solution Overview
Problem
In the 3GPP CSFB architecture, existing solutions fail to reliably page user equipment (UE) for circuit-switched calls when there are network issues, such as MME crashes or transmission failures, leading to dropped calls due to synchronization problems between the UE and the network.
Innovation Solution
A method where a switching unit, like a mobile switching centre (MSC), starts a timer to detect if the selected MME is ready and maintains a list of alternative MMEs within the same pool, allowing it to switch to another MME for paging if the initial one is not ready, ensuring the UE can be reached and the call can be continued in the CS domain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the MSC pages the UE via the registered MME, then the paging procedure follows the standard protocol, but the call is lost if the MME crashes or becomes unreachable
Solution Approach 1:
The MSC stores alternative MME addresses in advance before any failure occurs. When the initially registered MME becomes unreachable, the MSC can immediately switch to using an alternative MME from the pre-stored list, avoiding the need for complex real-time discovery procedures and reducing call delivery failure.
Solution Approach 2:
The system prepares backup MME addresses beforehand to cushion against potential MME failures. This proactive approach ensures that if the primary MME crashes or becomes unreachable, the MSC already has alternative routing options ready, preventing call loss without requiring complex failure detection and recovery mechanisms.
2Use of energy by moving object
If the UE remains in IDLE state without periodic updates, then battery consumption is reduced, but synchronization problems occur when the MME crashes
Solution Approach 1:
The system implements feedback through periodic TAU procedures where the UE reports its status to the network. When the MME crashes, this feedback mechanism allows the network to detect the failure and trigger alternative paging procedures through other MMEs in the pool, maintaining reliability while allowing the UE to remain in IDLE state for extended periods.
Data Source
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AI summary
There is provided a method for a switching unit (MSC_I) in a network in which a user equipment (UE) is being adapted to be attached and connected to a 2G/3G network for performing circuit switched, CS, communication with the network, or being adapted to be attached to a LTE network, for performing packet switched, PS, communication, wherein the PS communication is adapted to be performed via a mobility management entity, MME, which may be arranged in a pool of MME's, the user equipment (UE) being adapted to receiving page signals (18) so as to inform the user of incoming calls, the switching unit (MSC_I) being adapted for issuing page signals (16-1; 16-2; 16-3) to MME nodes, - receiving (13) an incoming external CS call; - performing detection (20) of a first selected MME, as to whether the first selected MME is ready or not; - if detecting a not ready state (22) concerning the selected MME (MME_I1), selecting (24) an alternative MME and issuing a page message (16; 16-1) to the alternative MME (MME_I2) (16-1) belonging to the same pool of MME's as the first MME.