NAS Procedure Handling via Back-Off Timer Management
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Solution Overview
Problem
In LTE systems, user equipment (UE) is unable to perform Non-Access Stratum (NAS) procedures, such as initiating a PDP context activation or PDN connection, even when the network is not congested, leading to service denial.
Innovation Solution
A communication device and method that transmit specific session management messages to handle NAS procedures, including Activate PDP Context Request messages, Activate Secondary PDP Context Request messages, and PDN CONNECTIVITY REQUEST messages, while managing back-off timers to determine resource availability and adjust message transmission accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE is forbidden to transmit SM messages for deactivated APN to prevent network overload, then network resource protection is improved, but service accessibility deteriorates
Solution Approach 1:
The network sends a DEACTIVATE PDP CONTEXT REQUEST message with cause #39 'reactivation requested' in advance, preparing the UE for future service restoration. This preliminary action allows the UE to proactively reactivate the APN when resources become available, balancing network protection with service accessibility.
Solution Approach 2:
The invention changes the interpretation of the back-off timer parameter. When the timer is deactivated and cause #39 is received, the UE transitions from a forbidden state to an allowed state for transmitting SM messages. This parameter change enables dynamic adaptation between network protection and service restoration.
2Ease of operation
If the UE transmits SM messages for deactivated APN to initiate PDP context activation, then service accessibility is improved, but network overload increases
Solution Approach 1:
The network provides feedback through the DEACTIVATE PDP CONTEXT REQUEST message with cause #39, informing the UE when it is appropriate to reactivate the APN. This feedback mechanism prevents the UE from prematurely transmitting SM messages that could cause network overload, while still enabling service restoration when resources are available.
3Speed
If the back-off timer is deactivated to allow immediate message transmission, then service restoration speed is improved, but network congestion risk increases
Solution Approach 1:
The network performs preliminary assessment of resource availability before sending the DEACTIVATE PDP CONTEXT REQUEST message with cause #39. This preliminary action ensures that the UE only restores service when the network is prepared to handle the traffic, preventing congestion while enabling fast restoration.
Data Source
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AI summary
A communication device for handling a Non-Access Stratum (NAS) procedure comprises instructions of transmitting a first session management (SM) message related to an access point name (APN) to a network; receiving a second SM message comprising a SM cause of insufficient resources and a back off timer value of a back off timer indicating that the back off timer is deactivated from the network in response to the transmission the first SM message; being forbidden to transmit a third SM message for the APN to the network, when the back off timer is deactivated for the APN; receiving a fourth SM message from the network indicating to deactivate and to reactivate an activated SM context associated with the APN, when the back off timer is deactivated for the APN; and transmitting a fifth SM message related to the APN to the network.