5GSM Congestion Timer Handling in 5GS Networks
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Solution Overview
Problem
In 5G wireless communication systems, the handling of 5G session management (5GSM) congestion timers is unclear, particularly regarding the stopping of Single-Network Slice Selection Assistance Information (S-NSSAI) based backoff timers when receiving specific messages or commands, leading to ambiguity in network operations.
Innovation Solution
A User Equipment (UE) is instructed to stop both the backoff timers applied to all Public Land Mobile Networks (PLMNs) and the registered PLMN in response to certain 5GSM messages, such as PDU session release commands or congestion control messages, and start new timers based on provided values, ensuring consistent timer management across different PLMN types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If S-NSSAI based backoff timers are applied to either registered PLMN or all PLMNs based on 5GSM congestion re-attempt indicator, then congestion control flexibility is improved, but timer management ambiguity increases
Solution Approach 1:
The patent changes the state parameters of backoff timers by introducing explicit stopping conditions based on 5GSM message types and cause values. When specific messages are received (PDU session release with cause #39, PDU session modification, PDU session authentication, or messages containing congestion control BO timer values), the timer state transitions from running to stopped, providing clear parameter change rules that resolve the ambiguity while maintaining flexibility.
Solution Approach 2:
The patent makes the timer management dynamic by allowing timers to be started, stopped, and restarted based on real-time network conditions and message exchanges. The backoff timer behavior adapts dynamically to different 5GSM scenarios, transitioning between different states (running/stopped) based on received messages, thereby providing both flexibility and clarity through state-based control.
2Reliability
If both BO timer applied to registered PLMN and BO timer applied to all PLMN run concurrently, then congestion control coverage is improved, but system complexity increases
Solution Approach 1:
The patent segments the backoff timer management into two distinct types: one applied to registered PLMN and another applied to all PLMNs. Each timer type is independently managed with clear stopping conditions, allowing concurrent operation without excessive complexity. The segmentation enables precise control over which timer stops under which conditions, maintaining reliability while managing complexity through structured separation.
3Speed
If UE stops running BO timer upon receiving specific 5GSM messages, then network response time is improved, but timer consistency challenges arise
Solution Approach 1:
The patent implements feedback mechanisms where the UE monitors incoming 5GSM messages and their cause values, then responds by stopping timers under specific conditions. The feedback loop ensures that timer stopping decisions are based on explicit network indications (cause #39, modification commands, authentication commands), providing fast response while maintaining consistency through rule-based decision making that considers the current timer state and message context.
Data Source
AI summary
In 5GS, Single-Network Slice Selection Assistance Information (S-NSSAI) based backoff (BO) timers (T3584/T3585) can be applied to either the registered PLMN or all the PLMNs based on a 5GSM congestion re-attempt indicator. For a specific PDU session, the corresponding BO timer applied to the registered PLMN and the BO timer applied to all PLMN can be both running concurrently. It is proposed for a UE to stop both the BO timer applied to all the PLMNs and the BO timer applied to the registered PLMN, if running, in all the following scenarios: 1) Receiving a PDU session release command without a BO timer, 2) Receiving a PDU session release command with 5GSM cause #39, 3) Receiving a PDU session modification command, 4) Receiving a 5GSM message with a 5GSM congestion control BO timer value, and 5) Receiving a PDU session authentication command.