NR V2X Sidelink DRX Timing Using Resource Allocation Feedback
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Solution Overview
Problem
In sidelink communication, receiving UEs continue to run the SL DRX timer unnecessarily due to unknown last transmission by transmitting UEs, leading to power inefficiency and potential packet delay budget exceedance.
Innovation Solution
Implementing a method where receiving UEs check the last physical sidelink control channel transmission and stop the SL DRX timer based on resource allocation information, and transmit SL HARQ feedback to manage power consumption effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the RX UE continues to run the SL DRX timer after receiving the last PSCCH/PSSCH transmission, then the RX UE can detect potential retransmissions, but the power consumption increases and the packet delay budget may be exceeded
Solution Approach 1:
The TX UE sends feedback information (such as HARQ NACK) to the RX UE to indicate that the current PSCCH/PSSCH transmission is the last one. The RX UE uses this feedback to stop the SL DRX timer after successfully receiving the transmission, thereby avoiding unnecessary power consumption while maintaining reliable detection of retransmissions when needed
Solution Approach 2:
The system pre-establishes a mechanism where the TX UE informs the RX UE about the last transmission status before actually stopping the timer. This preliminary notification allows the RX UE to make an informed decision about whether to continue running the timer or stop it, optimizing the balance between reliability and power consumption
2Reliability
If the RX UE starts the SL DRX timer after receiving PSCCH/PSSCH following an SL HARQ NACK, then the RX UE can ensure packet delivery, but the timer may exceed the packet delay budget and cause power waste
Solution Approach 1:
The RX UE uses feedback information from the TX UE (such as HARQ NACK status) to determine whether to start the SL DRX timer after receiving PSCCH/PSSCH. When the feedback indicates that the current transmission is the last one, the RX UE stops the timer, preventing packet delay budget exceedance and power waste while still ensuring packet delivery when necessary
3Use of energy by moving object
If the RX UE stops the SL DRX timer based on resource allocation information, then power savings are achieved, but the complexity of timer management increases
Solution Approach 1:
The system uses feedback information (resource allocation information, HARQ status) from the TX UE to automatically control the RX UE's timer behavior. This feedback mechanism simplifies timer management by providing clear instructions on when to start and stop the timer, reducing the complexity that would otherwise arise from managing multiple timer states and conditions
Data Source
AI summary
Proposed, in an embodiment, is a method for a first device to perform wireless communication. The method may comprise the steps of: establishing a radio resource control (RRC) connection with a second device; receiving, from the second device, a sidelink discontinuous reception (SL DRX) configuration including information related to an SL DRX cycle and information related to a timer for an active time; starting the timer; receiving first sidelink control information (SCI) for scheduling a physical sidelink shared channel (PSSCH), the first SCI being received from the second device through a physical sidelink control channel (PSCCH) on the basis of a first resource; and receiving second SCI and data from the second device through the PSSCH on the basis of the first resource. For example, the first SCI may include resource allocation information. For example, the timer may be stopped on the basis of the resource allocation information only including information about the first resource.