Core Network Mobile Reachable Timer Management for Emergency PDN Access
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Solution Overview
Problem
In wireless communication systems, network congestion leads to delays in high-priority and emergency services due to the inability to accurately track UE activity when back-off timers are active, causing potential loss of network reachability and service disruptions.
Innovation Solution
The core network implements a method to manage mobile reachable timers by resetting them to a value that reflects the remaining time of the MM back-off timer, ensuring continuous tracking of UE activity even during congestion, and allowing emergency PDN connections while preventing network detachment during active back-off periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the MME/SGSN enforces the stored back-off time by rejecting any subsequent request from the UE before the back-off time is expired, then network congestion is controlled, but the UE cannot access high priority services or emergency services causing service delay
Solution Approach 1:
The patent applies local quality by differentiating between regular services and high priority/emergency services in the congestion control mechanism. The MME/SGSN identifies the service type and applies different handling: regular services are rejected during back-off period, while high priority/emergency services are allowed to proceed. This selective approach maintains congestion control for normal traffic while ensuring critical services remain accessible.
2Reliability
If the mobile reachable timer is reset to its initial value after emergency PDN disconnection, then the timer can track future UE activity, but the network loses track of UE activity during the remaining back-off period
Solution Approach 1:
The patent implements feedback by having the UE inform the network about the remaining back-off timer value when disconnecting emergency PDN connection. The UE includes this information in the PDN disconnect request or deactivate bearer accept message. The network uses this feedback to adjust the mobile reachable timer accordingly, ensuring continuous tracking without gaps.
3Adaptability or versatility
If the network allows UE to initiate procedures for high priority service during back-off timer, then emergency service access is enabled, but the congested APN has no resources causing rejection and delay
Solution Approach 1:
The patent applies preliminary action by having the network pre-allocate or reserve resources for high priority and emergency services before congestion occurs. When congestion is detected, the MME/SGSN identifies available resources for high priority services and allows these procedures to proceed even during back-off period. This preliminary resource preparation ensures that emergency services can be delivered without rejection or delay.
Data Source
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AI summary
A method of handling an emergency PDN connection when a back-off timer is running for a core network in a wireless communication system is disclosed. The method comprises starting a mobile reachable timer when a mobile device enters an idle mode, wherein the mobile reachable timer has a first timer value; accepting the emergency PDN connection; stopping the mobile reachable timer when the mobile device enters a connected mode to establish the emergency PDN connection; resetting the mobile reachable timer to a second timer value when a remaining time of the back-off timer is longer than a periodic area update timer; and restarting the mobile reachable timer according to the second timer value when the emergency PDN is disconnected.