Uplink Scheduling on Unlicensed Spectrum via Dynamic Grant Delay
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Solution Overview
Problem
The use of unlicensed radio resources in wireless communication systems is complicated by scheduling challenges that affect resource efficiency, latency, and throughput, particularly when scheduling nodes need to manage transmissions on shared unlicensed frequency bands without causing interference.
Innovation Solution
A method where a scheduling node detects whether it has transmitted or scheduled to receive on an unlicensed radio resource and adjusts the grant delay of a joint grant for uplink transmissions based on this detection, allowing for variable grant delays that optimize resource usage and minimize latency and overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a scheduling node schedules transmissions on unlicensed radio resources in advance, then resource allocation efficiency is improved, but transmission latency increases due to the need for clear channel assessment and potential deferrals
Solution Approach 1:
The scheduling node performs preliminary scheduling of uplink transmissions by sending grants in advance, allowing the wireless device to prepare for transmission. This preliminary action improves resource allocation efficiency while the grant delay mechanism manages the timing to balance latency requirements
Solution Approach 2:
The system dynamically adjusts the grant delay parameter based on channel conditions and scheduling requirements. The grant delay can be varied to optimize the balance between allowing sufficient time for clear channel assessment (reducing latency) and maintaining efficient resource allocation (improving productivity)
2Productivity
If the scheduling node transmits grants on the unlicensed radio resource, then resource efficiency is improved, but the reliability of grant transmission decreases due to potential channel busy conditions
Solution Approach 1:
The system incorporates a grant delay mechanism that provides a time buffer between grant transmission and the scheduled uplink transmission. This cushioning allows the scheduling node to monitor channel conditions and potentially retransmit or adjust grants if the initial transmission fails due to busy channel conditions, thereby maintaining resource efficiency while improving grant transmission reliability
Solution Approach 2:
The scheduling node receives feedback from wireless devices regarding transmission status and channel conditions. This feedback enables the scheduling node to adaptively adjust future grant transmissions, improving reliability by avoiding times when the channel is likely to be busy while maintaining efficient resource utilization
3Speed
If the grant delay is minimized to reduce latency, then transmission speed is improved, but the complexity of scheduling increases due to the need to coordinate with clear channel assessment timing
Solution Approach 1:
The system uses the grant delay parameter as a controllable variable to balance transmission speed and scheduling complexity. By adjusting this single parameter, the system can optimize transmission speed while the scheduling node maintains awareness of clear channel assessment timing requirements, avoiding excessive complexity in the scheduling mechanism
Data Source
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AI summary
A scheduling node (14) in a wireless communication system is configured for scheduling an uplink transmission on an unlicensed radio resource. The scheduling node (14) is configured to detect whether or not the scheduling node (14) has transmitted or scheduled to receive on the unlicensed radio resource in a subframe. The scheduling node (14) is also configured to transmit a joint grant with a grant delay that is based on whether or not the scheduling node (14) has transmitted or scheduled to receive on the unlicensed radio resource in a subframe according to the detecting. The grant delay is a delay between transmission of the joint grant and an earliest one of multiple subframes granted by the joint grant for uplink transmission on the unlicensed radio resource.