Sidelink Transmission Over Unlicensed Bands Using LBT
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Solution Overview
Problem
Current cellular systems face challenges in increasing throughput due to bandwidth limitations in licensed spectra, prompting the need for utilizing unlicensed frequencies for sidelink communications, while ensuring fair sharing with existing technologies like Wi-Fi networks.
Innovation Solution
The method involves performing a listen-before-talk (LBT) process with a random backoff to obtain a channel occupancy time (COT) for sidelink transmission on unlicensed bands, determining candidate resources, and selecting the earliest available resource for transmission, incorporating mechanisms like resource overbooking and cyclic prefix extension to align LBT completion with transmission slots.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a random backoff LBT process is performed to acquire COT on unlicensed bands, then fair coexistence with Wi-Fi and other unlicensed users is ensured, but transmission latency increases and throughput efficiency decreases
Solution Approach 1:
The UE performs sensing operations and determines candidate sidelink resources in advance before the LBT process completes. By preparing resource selections beforehand based on sensed channel conditions, the system reduces the time penalty associated with random backoff LBT, as resource determination doesn't need to wait for LBT completion
Solution Approach 2:
The patent dynamically adjusts the sensing window and resource selection timing based on the LBT process state. The UE can adaptively modify sensing parameters and resource candidate sets during the LBT backoff period, optimizing the balance between fair channel access and transmission latency
2Adaptability or versatility
If the LBT process completion time is not aligned with transmission slots, then channel access flexibility is maintained, but resource utilization efficiency decreases
Solution Approach 1:
The UE determines candidate sidelink resources and prepares transmission configurations in advance during the LBT backoff period. This preliminary resource preparation ensures that when LBT completes, the UE can immediately transmit on pre-selected resources without additional delay, aligning LBT completion with effective transmission start
Solution Approach 2:
The patent introduces an intermediary mechanism where the UE performs sensing and resource determination as a bridge between LBT channel access and actual transmission. This intermediary process allows the system to decouple the random nature of LBT completion from transmission slot alignment, using pre-determined resource candidates to ensure efficient resource utilization regardless of when LBT completes
Data Source
AI summary
A method for performing sidelink transmission over an unlicensed band is provided. The method includes performing a first-type listen-before-talk (LBT) process on the unlicensed band to obtain a channel occupancy time (COT) for the sidelink transmission. The first-type LBT process includes a random backoff process. Duration of the random backoff process is determined by a randomly generated LBT counter. The method further includes determining, based on a result from a sensing operation performed on the unlicensed band within a sensing window, a plurality of candidate sidelink resources on the unlicensed band within a sidelink resource selection window. The method also includes selecting, based on a completion time point of the first-type LBT process, a sidelink resource from the plurality of candidate sidelink resources. The method also includes performing the sidelink transmission within the obtained COT on the selected sidelink resource.