Sidelink HARQ Feedback Transmission in Unlicensed Spectrum
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Solution Overview
Problem
Current wireless communication technologies, such as 5G NR and LTE, face challenges in improving sidelink communication efficiency in unlicensed spectrum, particularly in ensuring reliable hybrid automatic retransmission request (HARQ) feedback transmission without performing listen-before-talk (LBT) procedures, which can lead to increased latency and reduced data rates due to channel sensing requirements.
Innovation Solution
The proposed solution involves transmitting a sidelink data signal followed by a gap period, where a receiving UE transmits an automatic gain control (AGC) signal to occupy the unlicensed frequency band, allowing for HARQ feedback transmission without performing LBT, thereby ensuring the channel remains available for the feedback signal and reducing latency and increasing data rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If HARQ feedback transmission is performed in unlicensed spectrum without LBT, then latency is reduced and data rate is increased, but channel availability and collision avoidance are compromised
Solution Approach 1:
The transmitting UE performs LBT before the data transmission to secure the channel in advance. The receiving UE then transmits HARQ feedback immediately after receiving the data signal without needing to perform LBT again, because the channel has already been secured by the transmitting UE's preliminary LBT action.
Solution Approach 2:
The patent introduces a gap portion as an intermediary time interval between the data transmission and HARQ feedback transmission. This gap allows the receiving UE to prepare and transmit feedback signals without requiring additional LBT procedures, effectively mediating between the data transmission and feedback transmission to eliminate redundant channel sensing.
2Reliability
If LBT is performed before HARQ feedback transmission, then channel availability is ensured, but latency increases and data rate decreases
Solution Approach 1:
The transmitting UE performs LBT before the data transmission to secure the channel in advance. The receiving UE then transmits HARQ feedback immediately after receiving the data signal without needing to perform LBT again, because the channel has already been secured by the transmitting UE's preliminary LBT action.
Solution Approach 2:
The patent introduces a gap portion as an intermediary time interval between the data transmission and HARQ feedback transmission. This gap allows the receiving UE to prepare and transmit feedback signals without requiring additional LBT procedures, effectively mediating between the data transmission and feedback transmission to eliminate redundant channel sensing.
3Ease of operation
If gap portion duration is increased, then receiving UE can properly switch from receive mode to transmit mode, but feedback transmission time is delayed
Solution Approach 1:
The gap portion duration is made dynamic and configurable rather than fixed. The receiving UE can switch from receive mode to transmit mode within this flexible time interval, and the gap duration can be adjusted based on specific operational requirements to balance mode switching needs with feedback transmission timing.
Data Source
AI summary
Certain aspects of the present disclosure provide techniques for slot format for sidelink communication. A method that may be performed by a user equipment (UE) includes transmitting a data signal; refraining from transmitting during a gap portion occurring in time after the transmission of the data signal, wherein the gap portion has a duration less than or equal to a threshold; receiving a feedback signal after the gap portion, wherein the feedback signal comprises at least a signal and hybrid automatic retransmission request (HARQ) feedback for the data signal; receiving another signal; and adjusting a gain applied to the other signal based on the signal.