NR Sidelink Keep-Alive Timing for Efficient Link Failure Detection
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Solution Overview
Problem
The existing LTE keep-alive procedure for device-to-device (D2D) communication in New Radio (NR) sidelink operations is not robust and inefficient, leading to unnecessary signaling and poor link quality monitoring in vehicle-to-everything (V2X) communications.
Innovation Solution
A flexible and efficient keep-alive procedure for NR sidelink operations, involving adaptive timer settings based on service requirements, reduced retransmissions, and selective acknowledgments to improve link quality monitoring and reduce signaling overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the existing LTE keep-alive procedure is used for NR sidelink operations, then device-to-device communication can be maintained, but unnecessary signaling overhead occurs and link quality monitoring becomes inefficient
Solution Approach 1:
The patent modifies the keep-alive procedure by changing key parameters: introducing a new timer T3102 with specific expiration conditions, adjusting the counter T3102 to track failed transmissions, and modifying the behavior of existing timers T310 and T311. These parameter changes enable more efficient link quality monitoring by triggering appropriate actions (radio link failure declaration, connection release) based on timer expiration and counter thresholds, thereby reducing unnecessary signaling while maintaining reliability.
2Reliability
If frequent keep-alive messages are transmitted to monitor link quality, then link reliability improves, but signaling overhead increases
Solution Approach 1:
The patent implements periodic action through the configured timer T3102, which triggers keep-alive message transmission at regular intervals defined by the upper layer. The timer ensures that link quality monitoring occurs periodically rather than continuously, balancing reliability requirements with signaling efficiency. When T3102 expires, a keep-alive message is transmitted and the timer is restarted, creating a controlled periodic monitoring mechanism that avoids excessive signaling.
Solution Approach 2:
The patent employs feedback mechanisms through counters (T3102, T310) that track the number of failed transmissions and timer expirations. When the counter T3102 reaches a threshold or timer T310 expires, the system declares radio link failure and releases the connection. This feedback-based approach allows the system to adapt keep-alive message frequency based on actual link conditions, improving efficiency by reducing messages when the link is stable and maintaining reliability by increasing monitoring when degradation is detected.
3Speed
If the keep-alive timer is set to a short duration for rapid link failure detection, then link quality monitoring responsiveness improves, but false detections increase
Solution Approach 1:
The patent applies beforehand cushioning by introducing a buffer mechanism through the interaction of multiple timers (T3102, T310, T311) and counters. Before declaring radio link failure, the system allows timer T310 to expire and requires counter T3102 to reach a threshold, providing a cushion period that prevents premature failure declarations. This layered timing approach ensures that transient issues do not trigger false detections while still enabling rapid response to genuine link failures.
Data Source
AI summary
A method performed by a first user equipment (UE) configured for device-to-device (D2D) wireless communication. The method includes starting a keep-alive timer associated with a unicast sidelink (SL) connection with a second UE configured for D2D wireless communication. In response to expiration of the keep-alive timer, without receiving a transmission from the second UE while the keep-alive timer was running, a keep-alive message is transmitted to the second UE. In response to not receiving an acknowledgement of the keep-alive message, from the second UE within a predetermined duration, release of the unicast SL connection with the second UE is initiated without transmitting a further keep-alive message to the second UE.