PSCCH-Based Sidelink COT Sharing for LBT Delay Reduction
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Solution Overview
Problem
The extension of NR sidelink (SL) operation to unlicensed spectrum in 5 GHz and 6 GHz requires efficient channel access mechanisms that align with existing New Radio-Unlicensed (NR-U) Listen-Before-Talk (LBT) methods to facilitate fair coexistence and minimize resource waste.
Innovation Solution
A wireless communications device shares its sidelink channel occupancy time (COT) with another device by transmitting novel COT sharing information via physical Sidelink Control Channel (PSCCH), including a channel access priority class, a COT-sharing indicator, and a COT duration field, allowing efficient resource utilization and rapid data exchange without additional LBT.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a device performs random backoff LBT before channel access, then fair coexistence in unlicensed spectrum is achieved, but channel access delay and overhead increase
Solution Approach 1:
The patent applies preliminary action by having the first UE perform the random backoff LBT procedure in advance to acquire channel occupancy time (COT), then share this pre-acquired channel access opportunity with the second UE. The second UE can transmit without performing its own LBT within the shared COT period, thus resolving the contradiction by preparing the channel access in advance and reusing it, reducing delay while maintaining fair coexistence through the initial LBT.
2Reliability
If each UE performs independent LBT before transmission, then channel access fairness is maintained, but resource utilization efficiency decreases
Solution Approach 1:
The patent merges the channel access operations by allowing the second UE to utilize the first UE's acquired COT for its transmissions. Instead of each UE performing independent LBT, the second UE combines its transmission opportunities with the first UE's already-acquired channel access, thereby improving resource utilization efficiency while the initial LBT by the first UE maintains channel access fairness.
3Device complexity
If COT sharing information is transmitted via PSCCH, then overhead is reduced compared to separate signaling, but control channel capacity is consumed
Solution Approach 1:
The patent applies universality by using the PSCCH (Physical Sidelink Control Channel) for multiple purposes: it carries both regular sidelink control information and the COT sharing information. By making the PSCCH multi-functional, the patent reduces the need for separate dedicated signaling channels for COT sharing, thereby reducing overall signaling overhead while consuming control channel capacity only within the existing PSCCH framework.
Data Source
AI summary
A first wireless communications device, e.g., a first UE, shares a second portion, e.g., a remaining unused portion, of its sidelink (SL) channel occupancy time (COT), corresponding to unlicensed spectrum, with a second wireless communications device. The first wireless communications device communicates SL COT sharing information to the second wireless communications device via sidelink control information (SCI) communicated over physical sidelink control channel (PSCCH) resources during a first portion of its SL COT. In some embodiments, the SL COT sharing information includes one or more of: i) a channel access priority class value, ii) a COT-sharing indicator value, or iii) a COT duration field value. The SL COT sharing information allows the second wireless communications device to identify the second portion of the COT, which the second wireless communications device is allowed to use for reverse transmission to the first wireless communications.