NR-U System Information Update Notification Mechanism
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Solution Overview
Problem
In 5G NR-U systems, there are challenges with ensuring all user equipment (UEs) receive system information (SI) update notifications, leading to potential malfunction and network disturbances due to unreliable paging message delivery in unlicensed spectrum, where the network cannot guarantee delivery of SI updates in all paging occasions within a modification period.
Innovation Solution
Implementing proactive and reactive algorithms to enhance SI update notification reliability, including extending the notification period and retroactive transmissions, with indicators in the SI update notification message specifying when the UE should acquire the updated SI, ensuring timely updates even if initial notifications are missed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If periodic broadcasting of system information is used in NR-U, then UEs can receive SI updates, but delivery reliability is compromised in unlicensed spectrum due to channel access uncertainties
Solution Approach 1:
The network performs preliminary actions by sending multiple paging messages before the SI modification period to notify UEs in advance. This proactive notification approach ensures that UEs have sufficient time to prepare for SI updates, compensating for the unreliable delivery conditions in unlicensed spectrum.
Solution Approach 2:
The network monitors whether UEs have successfully received SI update notifications and implements retransmission mechanisms. This feedback-based approach allows the system to adapt to delivery failures by sending additional notifications until UEs confirm receipt or the update deadline approaches.
2Reliability
If multiple paging messages are sent to ensure delivery, then reliability improves, but network resources and time are consumed
Solution Approach 1:
Multiple paging messages are transmitted in advance of the SI modification period, distributing the notification burden over time rather than concentrating it at the last moment. This approach spreads resource consumption while ensuring UEs receive notifications despite channel uncertainties.
Solution Approach 2:
The notification mechanism uses periodic paging transmissions at defined intervals before the SI update. This structured periodic approach balances reliability improvement with controlled resource usage, avoiding continuous or excessive messaging.
3Reliability
If SI update notifications are sent in advance, then UEs can prepare for updates, but the notification period extends beyond a single modification period
Solution Approach 1:
The system implements preliminary notification by sending paging messages in advance of the actual SI modification period. This allows UEs to prepare for upcoming updates while maintaining a defined relationship between notification time and update execution time.
Solution Approach 2:
The notification period is made dynamic rather than fixed, allowing the network to adjust the timing and number of paging messages based on channel conditions and UE feedback. This flexibility optimizes the balance between advance preparation time and overall notification duration.
Data Source
AI summary
According to some embodiments, a method performed by a network node for updating system information (SI) in unlicensed spectrum includes determining to perform a SI update at a SI modification time, and for each SI update period of a plurality of SI update periods remaining before the SI modification time, transmitting a SI update notification to a wireless device. The SI update notification includes an indication of a SI modification time for when the UE should acquire updated SI. In some embodiments, the method further includes determining that the SI modification time has passed and that the SI update notification was not sent successfully for at least one SI update period of the plurality of SI update periods and transmitting a SI update notification to a wireless device including an indication that the wireless device should acquire updated SI immediately.