Scheduling Request Handling for URLLC Latency Reduction
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Solution Overview
Problem
In 5G wireless communication systems, the existing mechanisms for scheduling requests (SR) often lead to unnecessary latency and failure to meet quality of service (QoS) requirements for ultra-reliable low-latency communication (URLLC) traffic due to collisions with ongoing uplink-shared channel (UL-SCH) transmissions, particularly when UL-SCH resources do not meet logical channel prioritization (LCP) mapping restrictions.
Innovation Solution
A method for a terminal to determine whether to cancel a scheduling request, where the SR is not cancelled when a buffer status report (BSR) indicator is included in a protocol data unit, and the SR is transmitted responsive to an uplink grant, even if the UL-SCH resources do not initially meet LCP mapping restrictions, allowing for prioritization of high-priority data transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a scheduling request is cancelled when a buffer status report indicator is included in a protocol data unit, then resource efficiency is improved, but latency increases for high-priority URLLC traffic
Solution Approach 1:
The patent applies local quality by differentiating the cancellation behavior based on the priority of the logical channel. High-priority URLLC traffic maintains SR transmission even when BSR MAC CE is included, while low-priority eMBB traffic follows the traditional cancellation behavior. This selective application of the cancellation rule resolves the contradiction by preserving latency-critical URLLC performance while maintaining resource efficiency for non-critical traffic.
Solution Approach 2:
The patent introduces dynamic behavior by making the SR cancellation decision dependent on the logical channel priority associated with the triggered SR. The system dynamically adjusts whether to cancel or transmit the SR based on the priority level, allowing flexible adaptation to different traffic requirements. This dynamic approach enables the system to optimize both resource efficiency and latency performance under different conditions.
2Device complexity
If scheduling request configuration is mapped to physical uplink control channel with long period, then device complexity is reduced, but productivity decreases for time-sensitive communications
Solution Approach 1:
The patent applies segmentation by separating the SR configuration into different periods based on logical channel priority. High-priority URLLC logical channels are associated with short-period PUCCH configurations for rapid SR transmission, while low-priority eMBB logical channels use long-period configurations to reduce overall system complexity. This segmented approach allows the system to maintain simple configurations for non-critical traffic while providing fast response for critical traffic.
Data Source
AI summary
A method performed by a terminal in a wireless network for determining whether to cancel a scheduling request is provided. The method includes determining that a scheduling request is triggered for requesting an uplink resource for transmission of data to a network node. The method further includes, responsive to an uplink grant from the network node, transmitting the scheduling request to the network node without a cancellation of the scheduling request occurring due to a buffer status report indicator included in a protocol data unit of the terminal.