DCI Format 2_0 COT Indication for NR Unlicensed Spectrum
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Solution Overview
Problem
The increasing number of user equipment (UEs) in next-generation wireless communication systems leads to scarcity in licensed spectrum, resulting in insufficient bandwidth and reduced communication quality, necessitating the use of unlicensed spectrum for NR-based networks, where channel occupancy time (COT) indication is crucial for efficient resource sharing.
Innovation Solution
Modifying the Downlink Control Information (DCI) format 2_0 to include a Channel Occupancy Time (COT) indication, allowing base stations (gNBs) to inform UEs about the duration of channel occupancy, enabling efficient resource allocation and sharing by indicating the length of COT through additional fields or modifications in DCI format 2_0, such as adding a COT length field or using specific RNTIs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If unlicensed spectrum is used to provide additional communication channels, then bandwidth is improved, but channel access coordination and resource sharing become more complex
Solution Approach 1:
The gNB performs channel sensing and acquires Channel Occupancy Time (COT) before transmitting data to UEs. By preliminarily securing the channel and indicating the COT duration to UEs via DCI format 2_0, the gNB enables UEs to know in advance when they can transmit or should sleep, avoiding complex real-time coordination and collisions in the unlicensed spectrum.
2Productivity
If COT indication is implemented through DCI format modifications, then resource allocation efficiency is improved, but control signaling overhead increases
Solution Approach 1:
DCI format 2_0, originally designed for slot format indication, is enhanced to serve multiple purposes: it continues to indicate slot formats while also carrying COT indication information. This multi-functionality allows the system to convey both slot configuration and channel occupancy timing without adding separate dedicated signaling channels, thereby improving resource allocation efficiency while limiting the increase in control overhead.
3Reliability
If UEs are required to continuously monitor channel occupancy status, then communication reliability is improved, but energy consumption increases
Solution Approach 1:
The gNB provides preliminary COT indication to UEs through DCI format 2-0, informing them in advance of the channel occupancy duration. Armed with this prior information, UEs can confidently enter sleep mode during indicated COT periods without continuously monitoring channel status, thereby maintaining communication reliability (they know when to expect transmissions) while dramatically reducing energy consumption by avoiding continuous monitoring.
Data Source
AI summary
Devices and methods of providing channel occupancy time (COT) are described. After a gNB acquires an unlicensed channel for a COT, the gNB indicates the COT length to a UE using a PDCCH having a DCI formed in accordance with DCI format 2_0. The slot format of the last slot of the COT is indicated using a reserved slot format indicator that is reserved to indicate the end of the COT. The reserved slot format indicator indicates a last slot format of available slot formats of DCI format 2_0. Dummy bits fill the DCI after the reserved slot format indicator. Alternatively, to indicate the COT length, a COT field dedicated to providing the COT is used in the DCI or the CRC is masked using a slot format indication Radio Network Temporary Identifier.