Terminal LBT Coordination for Device-to-Device COT Sharing
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Solution Overview
Problem
In newly-operated frequency bands with higher frequencies, device-to-device direct communication in an unlicensed band requires compliance with regulations such as LBT, where COT sharing is necessary but may face LBT failures among multiple terminals.
Innovation Solution
A terminal performs LBT without random back-off for immediate transmission in a COT, transmits a second signal upon successful LBT, and manages transmission based on Cyclic-Prefix extension starting positions to avoid resource conflicts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LBT with random back-off is performed for channel access in unlicensed band, then collision avoidance is improved, but transmission delay increases and productivity decreases
Solution Approach 1:
The patent applies dynamic LBT operation by switching between two modes: Type 1 LBT with random back-off for initial channel access, and Type 2 LBT without random back-off for subsequent transmissions within the same COT. This dynamic adaptation allows the system to optimize between collision avoidance and transmission efficiency based on the transmission stage, resolving the contradiction between reliability and productivity.
2Productivity
If COT sharing is implemented among multiple terminals, then resource utilization is improved, but LBT failure probability increases
Solution Approach 1:
The patent introduces a coordination mechanism where the first terminal acts as an intermediary by notifying other terminals about its COT acquisition and intended transmissions. This allows second and third terminals to adjust their LBT operations accordingly - performing Type 2 LBT without random back-off when coordinated, thereby reducing LBT failures while maintaining efficient resource utilization through COT sharing.
3Loss of time
If Type 2 LBT without random back-off is used for immediate transmission, then transmission delay is reduced, but collision risk increases
Solution Approach 1:
The patent applies preliminary anti-action by having the first terminal perform Type 1 LBT with random back-off before acquiring COT, and then notify other terminals of its transmission plans. This preliminary action creates a protective framework that allows subsequent terminals to safely use Type 2 LBT without random back-off, reducing their transmission delay while the first terminal's preliminary LBT prevents collisions.
Data Source
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AI summary
A terminal includes: a reception unit configured to perform an LBT (Listen before talk) without a random back-off, the LBT being performed for performing transmission in a unit time immediately after a first signal related to device-to-device direct communication, the first signal being transmitted in a COT (Channel occupancy time) obtained by one of terminals in an unlicensed band; a transmission unit configured to transmit a second signal in a case where the LBT is successful; and a control unit configured to detect a reservation of a third signal that is to be transmitted in the unit time by another terminal. In a case where a plurality of CPE starting positions can be applied to the second signal and the third signal, the control unit excludes a resource in the unit time from transmission candidates or performs transmission in the unit time, based on a CPE (Cyclic-Prefix extension) starting position that is applied to the third signal.