Uplink Grant Scheduling for Reducing LBT Operations in 5G NR
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Solution Overview
Problem
Current solutions for uplink transmission in 5G new radio (NR) systems face challenges in efficient spectrum utilization and retransmission delays due to the need for frequent carrier sensing and channel occupation time constraints, particularly in multi-subframe scheduling scenarios, which can lead to reduced throughput and increased packet disorder.
Innovation Solution
The proposed method involves transmitting a first grant for uplink transmission over a first carrier and, upon specific trigger events such as transmission errors or changes in radio link quality, transmitting a second grant over a different carrier to override or update the first grant, allowing for retransmissions or continued transmissions within the same maximum channel occupation time without requiring additional carrier sensing, thereby reducing the number of LBT operations and enhancing spectrum utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carrier sensing is performed frequently for uplink transmission scheduling, then channel availability is ensured, but retransmission delays increase and throughput decreases
Solution Approach 1:
The eNB performs carrier sensing in advance before scheduling uplink transmissions. By determining channel availability beforehand and using this information to schedule multiple uplink grants within a maximum channel occupation time, the system ensures channel availability while reducing the need for frequent repeated sensing operations, thereby improving throughput.
2Adaptability or versatility
If maximum channel occupation time is enforced strictly, then fair sharing with other systems is ensured, but retransmission opportunities are delayed
Solution Approach 1:
The system dynamically schedules multiple uplink grants within the maximum channel occupation time based on trigger events such as transmission errors or radio link quality changes. This allows the eNB to allocate retransmission opportunities efficiently within the time constraint, enabling quick retransmissions without exceeding the maximum channel occupation time, thus maintaining coexistence while minimizing retransmission delays.
3Productivity
If multiple uplink transmissions are scheduled within same carrier, then spectrum utilization improves, but channel conflicts increase
Solution Approach 1:
The eNB performs carrier sensing before scheduling multiple uplink transmissions on the same carrier. By using the sensing result to determine whether to schedule multiple grants within the maximum channel occupation time, the system optimizes spectrum utilization while preventing channel conflicts through advance channel availability verification.
4Reliability
If additional carrier sensing is performed for retransmissions, then channel availability is confirmed, but the number of LBT operations increases
Solution Approach 1:
The eNB performs carrier sensing in advance and uses this information to schedule multiple uplink grants within a maximum channel occupation time. This preliminary sensing allows the system to confirm channel availability for retransmissions without requiring additional LBT operations, as the channel status is already known from the initial sensing performed before the first transmission.
Data Source
AI summary
Method, base station and user equipment are disclosed for uplink transmission and control thereof. A base station transmits to a user equipment a first grant that schedules a first uplink transmission in a first at least one subframe over a first carrier. In response to a trigger event, the base station determines a second grant that schedules a second uplink transmission over the first carrier. The base station transmits the second grant to the UE over a second carrier that has a different frequency than the first carrier.