Semi-Static Channel Access Method for Unlicensed Band Scheduling
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Solution Overview
Problem
Current communication systems face challenges in determining the channel occupancy time (COT) initiator for scheduled uplink transmissions in unlicensed bands, particularly in cross-FFP scheduling scenarios.
Innovation Solution
A semi-static channel access method is proposed for user equipment (UE) and base stations, involving the reception of downlink control information (DCI) within a fixed frame period (FFP), derivation of the COT initiator for each scheduled uplink transmission, and determination of transmission symbols based on the derived initiator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If cross-FFP scheduling is implemented to enable flexible uplink transmission scheduling across multiple fixed frame periods, then scheduling flexibility and resource utilization are improved, but the complexity of determining COT initiator and managing channel access increases
Solution Approach 1:
The base station performs preliminary channel access and COT initiation before scheduling uplink transmissions across multiple FFPs. The DCI format 0_1 includes pre-configured channel access parameters (priority classes, LBT thresholds) that the UE uses for subsequent transmissions, eliminating the need for complex real-time COT initiator determination by the UE.
Solution Approach 2:
The DCI format 0_1 acts as an intermediary carrying explicit COT initiator indication and channel access parameters from the base station to the UE. This intermediary structure resolves the complexity by providing clear, pre-determined channel access instructions rather than requiring the UE to independently determine COT initiator status.
2Reliability
If explicit COT initiator indication is included in DCI format 0_1 to resolve ambiguity in cross-FFP scheduling, then reliability of channel access control is improved, but the size and complexity of control information increases
Solution Approach 1:
The DCI format 0_1 is enhanced to serve multiple functions simultaneously: it carries uplink scheduling grants, includes COT initiator indication, and provides channel access parameters. This multi-functionality approach consolidates control information into a single structured format rather than requiring separate signaling messages.
Solution Approach 2:
The DCI format 0_1 includes configurable channel access parameters (priority classes, LBT thresholds, COT lengths) that can be adjusted based on service requirements. These parameter changes allow flexible adaptation to different channel access scenarios while maintaining a unified control structure.
3Adaptability or versatility
If multiple channel access parameters are configured for different priority classes to support diverse uplink services, then service differentiation and QoS are improved, but the complexity of parameter management and configuration increases
Solution Approach 1:
Channel access parameters are segmented into distinct priority classes (0-3) with specific parameter sets for each class. Each priority class has pre-defined LBT thresholds, COT lengths, and other parameters, allowing service differentiation through simple class identification rather than complex individual parameter management.
Solution Approach 2:
The system dynamically selects appropriate channel access parameters based on the priority class of the uplink service. High-priority services (e.g., URLLC) use priority class 0 with relaxed LBT requirements, while lower-priority services use higher priority classes with stricter parameters, enabling adaptive resource allocation.
4Reliability
If UE performs LBT before scheduled uplink transmissions in cross-FFP scenarios to ensure channel availability, then channel access reliability is improved, but transmission delay and latency increase
Solution Approach 1:
The base station performs preliminary channel access and secures a COT spanning multiple FFPs before scheduling uplink transmissions. The UE inherits the COT rights through DCI indication, eliminating the need for UE to perform LBT before scheduled transmissions within the granted COT period.
Solution Approach 2:
The COT is configured to span continuously across multiple FFPs, allowing uninterrupted uplink transmissions without repeated LBT procedures. This continuous channel access maintains reliability while minimizing delays by avoiding repeated channel sensing interruptions.
Data Source
AI summary
A user equipment (UE) executes a semi-static channel access method in an unlicensed band. The UE receives a first downlink control information (DCI) within a fixed frame period (FFP), wherein the first DCI is for scheduling uplink (UL) transmissions over one or more FFPs. The UE derives, for each scheduled UL transmission of the scheduled UL transmissions, a channel occupancy time (COT) initiator of the scheduled UL transmission. The UE determines one or more transmission symbols for each of the scheduled UL transmissions according to the derived COT initiator. The UE transmits each of the scheduled UL transmissions in the one or more transmission symbols of the one or more FFPs.