Network Access Node Time-Synchronization Control for URLLC
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Solution Overview
Problem
Current 4G wireless communication systems face challenges in maintaining ultra-reliable and low-latency connections, particularly for services requiring stringent latency and reliability, such as industrial control, traffic safety, and medical applications, due to unpredictable latency and high block error rates, which are exacerbated by the need for continuous time-synchronization of user equipment with the serving cell during URLLC services.
Innovation Solution
A network access node is configured to transmit a control message to a client device when a time-synchronization event is triggered, instructing it to transmit a response signal to maintain uplink time-synchronization, using predefined control information structures and timing advance values to ensure continuous synchronization, thereby reducing signaling overhead and improving resource allocation and utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional 4G LTE time-synchronization methods are used, then basic wireless connectivity is maintained, but latency becomes unpredictable and exceeds the required 0.5 ms for URLLC services
Solution Approach 1:
The network access node transmits a control message to the client device before the time alignment timer expires, instructing it to transmit a response signal. This preliminary action ensures time-synchronization is maintained proactively rather than reactively, preventing latency issues before they occur and ensuring URLLC service requirements are met.
Solution Approach 2:
The system establishes a feedback loop where the network access node monitors the time alignment timer status and sends control messages to the client device based on this monitoring. The client device responds with a response signal, creating a closed-loop feedback mechanism that continuously maintains time-synchronization reliability while minimizing latency.
2Reliability
If continuous time-synchronization monitoring is implemented, then QoS is guaranteed for URLLC services, but signaling overhead increases
Solution Approach 1:
Instead of continuous monitoring, the system uses periodic monitoring through the time alignment timer mechanism. The network access node monitors at discrete intervals (when the timer expires or is about to expire), reducing signaling overhead while still maintaining sufficient QoS guarantee for URLLC services.
Solution Approach 2:
The client device autonomously manages its time-synchronization by transmitting the response signal upon receiving the control message, without requiring continuous network intervention. This self-service approach reduces signaling overhead while maintaining QoS through the client's autonomous time-keeping capabilities.
3Reliability
If time alignment timer expiry is used as the trigger point, then synchronization is maintained, but resource allocation flexibility is reduced
Solution Approach 1:
The network access node transmits the control message before the time alignment timer expires, using a time threshold value to determine the optimal transmission timing. This preliminary action maintains time-synchronization reliability while providing the network with flexibility in resource allocation, as it can schedule control messages at optimal moments rather than being forced to wait until timer expiry.
Data Source
AI summary
The application relates to maintaining time-synchronization of a wireless connection between a network access node and a client device. The wireless connection may be configured for services with latency constraints. In one example, based on an expiry of a time alignment timer for the client device, the network access node transmits a control message to the client device. The control message instructs the client device to transmit a response signal to the network access node. The response signal can be used by the network access node to determine the timing advance for the wireless connection and adjust the timing advance.