Sidelink DRX State Modeling for UE Power Saving
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Solution Overview
Problem
Conventional NR V2X approaches are not power efficient for non-vehicular sidelink use cases, such as NR V2X sidelink, NR Commercial sidelink, and NR Critical sidelink, due to the lack of consideration for power consumption in UE design, and issues in modeling sidelink DRX operations in multi-peer UE environments, especially during sidelink discovery and communication.
Innovation Solution
A sidelink state model is introduced to describe UE behavior for DRX operation, including power savings opportunities and various DRX models applicable to sidelink states, with mechanisms for enabling or disabling SL DRX and configuring it based on service type, cast type, and interaction with Uu DRX.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional NR V2X approaches are used for sidelink communication, then communication functionality is achieved, but power consumption is high due to continuous monitoring requirements
Solution Approach 1:
The patent implements discontinuous reception (DRX) cycles for sidelink communication where the UE alternates between active monitoring periods and sleep periods. During active periods, the UE monitors PSCCH for sidelink control information; during sleep periods, monitoring is suspended to save power. This periodic action allows the system to maintain communication functionality while significantly reducing power consumption compared to continuous monitoring.
2Use of energy by moving object
If DRX is implemented for power savings, then energy consumption is reduced, but complexity increases due to multiple DRX configurations and state management
Solution Approach 1:
The patent segments sidelink DRX operation into distinct states (SL_Inactive, SL_UnLinked, SL_Linked) with specific DRX behaviors for each state. This segmentation allows the system to manage complexity by defining clear state transition rules and state-specific configurations, making the overall DRX operation more tractable despite multiple configurations being involved.
Solution Approach 2:
The patent implements dynamic DRX configuration where parameters such as drx-onDurationTimer, drx-InactivityTimer, and cycle lengths can be adjusted based on sidelink activity conditions. The system dynamically transitions between short and long DRX cycles, and adjusts timer values based on observed sidelink traffic patterns, allowing adaptive power savings while maintaining communication reliability.
3Reliability
If continuous PSCCH monitoring is performed, then sidelink communication reliability is maintained, but power consumption increases
Solution Approach 1:
The patent implements periodic monitoring within DRX cycles where the UE monitors PSCCH during active periods and suspends monitoring during sleep periods. The drx-onDurationTimer defines the active monitoring duration, and the drx-InactivityTimer extends monitoring when sidelink activity is detected. This periodic approach maintains reliability by ensuring monitoring occurs at regular intervals while reducing power consumption by suspending monitoring between intervals.
Solution Approach 2:
The system uses feedback mechanisms where the UE monitors for sidelink control information during active periods and adjusts its DRX behavior based on detected activity. When sidelink traffic is detected, the drx-InactivityTimer is started or extended, keeping the UE in active state. When no traffic is detected for the timer duration, the UE transitions to sleep mode. This feedback-driven approach ensures reliability is maintained during active communication while enabling power savings during idle periods.
Data Source
AI summary
SL DRX mechanism is used for power savings, to address a number of sidelink non-vehicular sidelink use cases. Methods, systems, and apparatuses, among other things, as described herein may use 1) A sidelink state model to describe the UE behavior for sidelink DRX operation. The DRX operation tailored to each of the sidelink states; 2) Power savings opportunities during SL operation, in addition to stopping PSCCH monitoring; 3) Various DRX models applicable to the sidelink; 4) SL_DRX operation for the SL UnLinked state; or 5) SL DRX operation for the SL_Linked state.