NR Sidelink COT Sharing for Efficient Unlicensed Channel Access
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Solution Overview
Problem
Existing channel occupancy time (COT)-sharing methods for new radio (NR) sidelink (SL) communications in unlicensed bands face challenges due to inefficient resource allocation and LBT procedures, leading to potential channel loss and inefficiencies in unicast, groupcast, and broadcast communications.
Innovation Solution
Implementing COT-sharing indicators and signaling methods for NR SL in unlicensed bands, allowing UEs to determine and utilize time-frequency resources efficiently through COT-sharing protocols, including unicast, groupcast, and broadcast communications, while adhering to regulatory rules and enhanced mode-2 resource selection aspects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LBT procedure is performed to detect channel availability, then channel access reliability is improved, but channel occupancy time is extended beyond what is actually needed
Solution Approach 1:
The COT indicator is transmitted in advance to inform other UEs about the channel occupancy duration before the actual transmission completes. This allows receiving UEs to prepare for potential COT sharing opportunities ahead of time, resolving the contradiction by maintaining reliable channel access while optimizing the utilization of the occupied channel time.
2Adaptability or versatility
If COT-sharing protocol is implemented without central controller, then system autonomy and flexibility are improved, but protocol complexity and coordination difficulty increase
Solution Approach 1:
Each UE autonomously determines whether to share its COT with other UEs based on the received COT indicators and its own transmission needs. The system self-regulates channel access without requiring central controller intervention, with UEs independently making decisions about COT sharing based on pre-agreed protocols, thus achieving system autonomy while keeping individual device complexity manageable.
Solution Approach 2:
The COT indicator transmission creates a feedback mechanism where UEs inform others about their channel occupancy status. This feedback allows receiving UEs to adjust their channel access behavior accordingly, enabling autonomous coordination without central control while maintaining protocol simplicity through standardized indicator formats and decision rules.
3Ease of manufacture
If resource allocation works with slot granularity, then resource management simplicity is improved, but channel utilization efficiency deteriorates when LBT completes before or after slot boundary
Solution Approach 1:
The channel occupancy time is segmented into discrete indicator transmissions that can occur at flexible time points independent of slot boundaries. The COT indicator format allows for granular time specifications that can precisely mark the start and end of shareable COT periods, resolving the contradiction by maintaining simple slot-based resource management while enabling efficient channel utilization through flexible indicator timing.
Data Source
AI summary
Methods and systems are provided in which a channel occupancy time (COT)-sharing indicator is received, at a first user equipment (UE), from a second UE. The first UE determines whether the first UE is able to use a time-frequency resource within a frequency range indicated by the COT-sharing indicator received from the second UE. In case that the first UE is able to use a time-frequency resource within the frequency range, data is transmitted with COT-sharing between the first UE and the second UE. In case that the first UE is unable to use a time-frequency resource within the frequency range, the data is transmitted without COT-sharing in a first resource selected by the first UE.