NR V2X Sidelink Radio Link Monitoring for HARQ-Based Failure Detection
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Solution Overview
Problem
Existing wireless communication systems lack effective mechanisms for monitoring sidelink radio link failures (SL-RLF) and managing radio link quality in sidelink connections, which can impact the reliability and performance of vehicle-to-everything (V2X) communications.
Innovation Solution
An apparatus and method for sidelink radio link monitoring (SL-RLM) that includes processing circuitry to receive signals, perform SL-RLM measurements, and determine SL-RLF based on hybrid automatic repeat request (HARQ) feedback, radio link in-sync or out-of-sync conditions, and keep-alive messages, configuring lower protocol layers for SL-RLM, and transmitting measurements to a controlling entity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SL-RLM is implemented using multiple measurement quantities (HARQ feedback, radio link in-sync/out-of-sync, keep-alive messages), then the reliability of sidelink connection monitoring is improved, but the device complexity increases
Solution Approach 1:
The monitoring mechanism is segmented into multiple independent measurement quantities (HARQ feedback, radio link in-sync/out-of-sync indicators, keep-alive messages), each operating at different protocol layers. This segmentation allows the system to monitor link quality through diverse indicators without requiring a single complex monitoring mechanism, thereby improving reliability while managing complexity through modular design.
Solution Approach 2:
The SL-RLM mechanism is designed to perform multiple functions simultaneously using the same processing circuitry: evaluating HARQ feedback, assessing radio link synchronization status, and processing keep-alive messages. This multi-functionality approach improves reliability through comprehensive monitoring while avoiding the need for separate dedicated mechanisms for each function, thus controlling device complexity.
2Measurement precision
If SL-RLF detection is performed continuously using multiple signals, then the measurement precision is improved, but the use of energy increases
Solution Approach 1:
The monitoring mechanism evaluates multiple measurement quantities at periodic intervals rather than continuously. The processing circuitry assesses HARQ feedback, radio link indicators, and keep-alive messages at defined monitoring periods, which maintains accurate SL-RLF detection precision while significantly reducing energy consumption compared to continuous monitoring of all signals.
3Adaptability or versatility
If configuration information for SL-RLM is provided for multiple measurement quantities, then the adaptability of the monitoring system is improved, but the loss of information increases
Solution Approach 1:
Configuration information for all measurement quantities (HARQ feedback parameters, radio link threshold values, keep-alive message intervals) is provided in advance through higher-layer signaling before monitoring begins. This preliminary configuration enables the processing circuitry to adaptively monitor multiple signals without requiring real-time configuration exchanges, thereby maintaining system adaptability while minimizing information loss during operation.
Data Source
AI summary
An apparatus in accordance with the present application may monitor a sidelink (SL) connection. The apparatus includes processing circuitry that receives signals in a protocol stack to perform SL-radio link monitoring (SL-RLM), and determines, according to the signals, whether a SL-radio link failure (RLF) has occurred. The signals may include hybrid automatic repeat request (HARQ) feedback. In a case that the signals include a HARQ-NACK, the processing circuitry determines that the SL-RLF has occurred. The processing circuitry further receives configuration information related to the SL-RLM for the signals, the configuration information including configurations for measurement quantities of the signals and a condition for declaring SL-RLF, configures, according to the configuration information, lower layers of the protocol stack for the SL-RLM for the signals, and performs SL-RLM measurements of the measurement quantities.