Unlicensed Spectrum COT Scheduling for Low-Latency URLLC Uplink
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Solution Overview
Problem
Current channel occupancy time (COT)/fixed frame period (FFP) scheduling in unlicensed spectrum faces challenges, particularly in scenarios where UE-initiated COT is not supported, leading to issues like PUSCH segmentation and increased latency for urgent URLLC requests.
Innovation Solution
Implement flexible COT scheduling that allows for UE-initiated COT, with mechanisms such as RRC or DCI signaling to enable/disable UE-initiated behavior, and handle PUSCH segmentation by refraining from transmitting segments that overlap with idle periods or resuming transmission in subsequent COTs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If UE-initiated COT is not supported, then network control is maintained, but latency increases and segmentation issues occur for urgent URLLC requests
Solution Approach 1:
The system dynamically switches between gNB-initiated and UE-initiated COT modes based on traffic requirements. For URLLC traffic, UE-initiated COT is enabled to reduce latency, while for other traffic gNB-initiated COT is used to maintain network control. This dynamic adaptability resolves the contradiction between reliability and latency.
Solution Approach 2:
The network configures different COT parameters (such as cot-LengthDl, cot-LengthUl, pusch-TimeDomainOffset) based on the initiated COT type. By changing these parameters according to whether gNB or UE initiates the COT, the system optimizes both reliability and latency for different service types.
2Productivity
If PUSCH segmentation is implemented to avoid idle periods, then transmission timing is optimized, but device complexity increases
Solution Approach 1:
The PUSCH transmission is segmented into multiple parts when it overlaps with idle periods. The network configures multiple PUSCH resources with different time offsets, and the UE transmits only the segments that fall within the COT period. This segmentation approach improves transmission efficiency while keeping the complexity manageable through pre-configuration.
3Adaptability or versatility
If flexible COT scheduling is implemented, then adaptability improves, but system complexity increases
Solution Approach 1:
The network pre-configures multiple PUSCH resources with different time domain offsets and associates them with different initiated COT types. This preliminary configuration reduces real-time scheduling complexity while maintaining flexibility, as the UE can directly select from pre-configured resources based on the COT initiation type.
Solution Approach 2:
The system uses DCI signaling to indicate to the UE which PUSCH resource to use based on the COT initiation type. This feedback mechanism allows the network to maintain flexibility while simplifying UE implementation, as the UE follows clear network instructions rather than making complex decisions autonomously.
Data Source
AI summary
According to some embodiments, a method is performed by a wireless device for operation with shared spectrum channel access, wherein a first plurality of fixed frame periods (FFPs) are associated with the wireless device and a second plurality of fixed frame periods (FFPs) are associated with a network node and wherein each FFP comprises an idle period with no transmission and a channel occupancy time (COT) for potential transmission. The method comprises initiating a COT in one of the FFPs of the first plurality of FFPs and upon successful initiation of the COT, transmitting uplink data from the beginning of the COT.