Sidelink Communication Timing for LBT Failures in Unlicensed Bands
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Solution Overview
Problem
The increasing demand for mobile broadband communication and V2X services in wireless communication systems necessitates improved sidelink communication methods to handle larger capacities, reliability, and latency, particularly in unlicensed bands, where listen before talk (LBT) failures can disrupt data transmission.
Innovation Solution
A method and device for sidelink communication that includes obtaining DRX configuration, transmitting sidelink control information, performing LBT for PUCCH transmission, and starting a SL DRX HARQ RTT timer upon LBT failure to ensure reliable data transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If listen before talk (LBT) is performed for PUCCH transmission in unlicensed bands, then channel access reliability is improved, but transmission latency increases due to LBT failures
Solution Approach 1:
The patent performs LBT procedure in advance before PUCCH transmission to determine channel availability. By conducting the listen-before-talk check preliminarily, the system can prepare transmission resources ahead of time, reducing actual transmission latency while maintaining reliable channel access through proactive channel assessment
Solution Approach 2:
The patent introduces DRX HARQ RTT timer as an intermediary mechanism to manage the timing between LBT failure detection and subsequent retransmission. This timer acts as a controlled waiting period that balances channel access reliability with latency reduction, allowing the system to recover from LBT failures without excessive delay
2Duration of action of stationary object
If PUCCH transmission is performed after LBT failure, then data transmission continuity is improved, but interference to other devices increases
Solution Approach 1:
The patent applies preliminary anti-action by performing LBT procedure to detect ongoing transmissions before initiating PUCCH transmission. When LBT detects channel busy status, the system refrains from transmitting, thereby preventing interference to other devices while maintaining data transmission continuity through alternative scheduling or retransmission mechanisms
3Productivity
If SL DRX HARQ RTT timer is started immediately after LBT failure, then HARQ process efficiency is improved, but timing synchronization with base station deteriorates
Solution Approach 1:
The patent dynamically adjusts the SL DRX HARQ RTT timer start timing based on whether PUCCH transmission was performed. When LBT failure prevents PUCCH transmission, the timer starts at a modified time point rather than immediately, changing the temporal parameter to maintain synchronization with base station expectations while still improving HARQ efficiency through optimized retransmission timing
Data Source
AI summary
A method performed by a first device and a device supporting same in a wireless communication system are provided. The method may include: obtaining discontinuous reception (DRX) configuration information a sidelink (SL) DRX hybrid automatic repeat request (HARQ) round trip time (RTT) timer; receiving, from a base station, a downlink control indicator (DCI) for scheduling a SL resource and a physical uplink control channel (PUCCH) on a physical downlink control channel (PDCCH); based on the SL resource, transmitting, to a second device, a first sidelink control indicator (SCI) for scheduling a physical sidelink shared channel (PSSCH) and a second SCI on a physical sidelink control channel (PSCCH); based on the SL resource, transmitting, to the second device, the second SCI including information related to a SL HARQ process, and data on the PSSCH; performing a listen before talk (LBT) for a PUCCH transmission; and based on that a PUCCH resource is configured, and the PUCCH transmission is not performed due to a LBT failure, starting the SL DRX HARQ RTT timer corresponding to the SL HARQ process in a first symbol after a PUCCH resource for a SL HARQ feedback, in the PUCCH resource.