UMTS Media Gateway Call Switchover via State Extraction
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Solution Overview
Problem
The standard UMTS IuUP protocol fails to transparently switch active calls between service cards in media gateways, leading to high call drop rates due to inadequate handling of acknowledgement responses and packet loss in UMTS networks, particularly when differentiating between negative and no acknowledgement scenarios.
Innovation Solution
A modified media gateway architecture with switchover handling modules that allow direct transition between states without sending INIT messages and the use of additional timers for acknowledgement retries, enabling transparent call switchover and reducing call drops by suppressing unnecessary protocol messaging and extending acknowledgement wait times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the standard IuUP protocol state machine is used to switch calls between service cards, then protocol compliance is maintained, but transparent switchover cannot be achieved because the protocol requires sending INIT messages and receiving acknowledgements
Solution Approach 1:
The patent extracts the essential call state information from the full IuUP protocol sequence and maintains only the necessary state data in memory. This allows the service card to be replaced without needing to re-establish the complete protocol state, enabling transparent switchover by preserving call state information independently of the physical card
Solution Approach 2:
The patent performs preliminary actions by saving call state information to memory before the service card failure occurs and restoring it after replacement. This preliminary preservation and restoration of state information enables the call to continue transparently without requiring INIT messages or acknowledgements during the switchover
2Reliability
If a single timer is used for acknowledgement handling, then quick decision-making is enabled for negative acknowledgements, but call drop rates increase in high packet loss scenarios where acknowledgements are lost
Solution Approach 1:
The patent implements dynamic timer adjustment where the acknowledgement timer value is not fixed but adapts based on network conditions and retry attempts. The timer can be extended for retry scenarios and reduced when quick failure detection is appropriate, allowing the system to balance between quick decision-making and maintaining calls in high packet loss environments
Solution Approach 2:
The patent changes the timer parameter from a single fixed value to multiple configurable values based on the scenario. Different timer durations are applied depending on whether it's a first attempt, a retry, or a negative acknowledgement case, optimizing both quick failure detection and call establishment reliability in challenging network conditions
3Reliability
If INIT messages are retransmitted multiple times in high packet loss scenarios, then call establishment probability increases, but call drop rates remain high due to timer expiration without proper differentiation between negative and no acknowledgement
Solution Approach 1:
The patent implements feedback mechanisms where the system monitors acknowledgement responses and adjusts retry behavior accordingly. When no acknowledgement is received, the system can retry with extended timers, and when negative acknowledgements are received, the system stops retries. This feedback-driven approach optimizes call establishment success while managing call setup time through intelligent retry logic
Data Source
AI summary
Methods and apparatus for transparently switching a local instance of a UMTS protocol-based call from a first card or module of a media gateway to a second card or module of the media gateway, such that the remote end of the call is not aware that the call has been switched between the first and second cards or modules. Moreover, initially establishing call media flow may include implementing two timers of different duration during which call-initialization is retried if no Positive-Acknowledgement of call initialization is received, where a shorter-duration timer is relied upon to attempt retries if a Negative-Acknowledgement is received, and a longer-duration timer is relied upon to attempt retries if neither a Positive-Acknowledgement nor a Negative-Acknowledgement is received.