MBS Session Back-Off Timer Handling for UE Rejoin Control
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Solution Overview
Problem
In 5G networks, the UE behavior upon receiving an 'MBS join is rejected' or 'Remove UE from the MBS session' decision from the network is undefined, leading to unclear handling of Multicast Broadcast Services (MBS) session management.
Innovation Solution
The UE associates a back-off timer with the MBS session ID upon receiving a rejection, and refrains from requesting to join the same MBS session until the timer expires, is switched off, USIM is removed, or network events occur, providing clear guidelines for session management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the UE continuously attempts to join MBS sessions without back-off timer handling, then the UE can quickly re-join sessions, but the network resources are wasted and session management becomes inefficient
Solution Approach 1:
The network performs preliminary action by setting a back-off timer before actually rejecting the UE's MBS session join request. This timer prevents the UE from immediately re-attempting to join the same session, allowing the network to prepare for future connection attempts while avoiding wasted resources on redundant rejection handling.
Solution Approach 2:
The patent implements feedback mechanisms where the network provides feedback information to the UE about session rejection reasons and back-off timer status. This enables the UE to adjust its behavior accordingly, understanding when and why it was rejected without continuously attempting to join, thus optimizing network resource utilization.
2Loss of energy
If the UE implements back-off timer handling for MBS session rejections, then network resource efficiency is improved, but the UE behavior becomes more complex
Solution Approach 1:
The UE performs self-service by automatically managing the back-off timer based on network instructions. Once the network sets the back-off timer, the UE autonomously handles the timing logic and determines when to retry the session join request, eliminating the need for complex external control mechanisms while maintaining resource efficiency.
Solution Approach 2:
The patent uses parameter changes by dynamically adjusting the back-off timer duration and state based on network conditions and rejection reasons. The timer parameter can be modified, extended, or expired based on feedback from the network, allowing the UE to adapt its behavior flexibly without implementing overly complex decision logic.
3Reliability
If the UE waits for back-off timer expiry before rejoining MBS session, then unnecessary requests are prevented, but the time to rejoin is extended
Solution Approach 1:
The back-off timer implementation introduces dynamic timing behavior where the UE automatically adjusts its rejoin attempt timing based on network-provided timer values. The system dynamically balances between preventing invalid requests and minimizing legitimate rejoin delays, adapting to different network conditions and rejection scenarios.
Solution Approach 2:
The patent implements periodic action through the back-off timer mechanism, where the UE is instructed to wait for a specified period before attempting to join the MBS session again. This periodic waiting pattern prevents immediate re-attempts that would waste network resources, while the timer expiry naturally defines when the UE can safely try again.
Data Source
AI summary
A method for handling the joining and leaving an MBS session via a PDU session establishment or modification procedure is provided. Upon receipt of a back-off timer in the Received MBS Container IE (with the operation/decision “MBS join is rejected” or “Remove UE from the MBS session”), the UE shall associate the MBS back-off timer with the MBS session ID (e.g., TMGI). If the timer value is neither zero nor deactivated, the UE should not request to join the MBS session with the same MBS session ID before the timer expiry. If the timer value is deactivated, the UE should not request to join the MBS session with the same MBS session ID until the UE is switched off, the USIM is removed, an entry in the “list of subscriber data” for the current SNPN is updated, or an event/notification is triggered by the network.