Grant-Free Uplink Transmission Reliability for URLLC
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Solution Overview
Problem
Current grant-free uplink transmission (GFUT) techniques in wireless communications, while offering near-zero channel access delay, fail to meet the reliability requirements for ultra-reliable low-latency communications (URLLC) and are not flexible enough to adapt to varying traffic demands.
Innovation Solution
The method involves selecting radio resources from two pools to transmit content in parallel, with the UE duplicating scheduling requests (SR) and data on both contention-based and scheduling-based channels, enhancing reliability and adaptability by using adaptive triggers and signaling elements to coordinate between SR and GFUT.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If grant-free uplink transmission is used, then channel access delay is reduced to near-zero, but reliability requirements for URLLC are not met
Solution Approach 1:
The patent segments the transmission approach by dividing resources into two distinct pools: contention-based resources for immediate access and scheduling-based resources for reliable delivery. This segmentation allows the system to exploit the low-latency advantage of contention-based access while simultaneously ensuring reliability through scheduling-based retransmissions and acknowledgments, thereby resolving the contradiction between speed and reliability
Solution Approach 2:
The patent implements dynamic resource allocation where the UE can adaptively select between contention-based and scheduling-based resources based on current channel conditions, traffic characteristics, and reliability requirements. This dynamic approach enables the system to optimize the trade-off between latency and reliability in real-time, improving overall URLLC performance
2Loss of time
If grant-free transmission is used, then near-zero channel access delay is achieved, but adaptability to different traffic demands is insufficient
Solution Approach 1:
The patent creates a universal resource pool structure where resources can serve multiple functions: contention-based resources handle immediate low-latency traffic, while scheduling-based resources accommodate varying traffic patterns and requirements. This multi-functionality enables the system to adapt to different traffic demands (packet sizes, arrival rates, reliability requirements) while maintaining the low-latency advantage of grant-free access
3Reliability
If scheduling/grant-based transmissions are used, then reliability requirements for URLLC are met, but latency increases
Solution Approach 1:
The patent applies preliminary action by pre-configuring two pools of resources (contention-based and scheduling-based) before transmission occurs. The UE can immediately attempt contention-based transmission without waiting for scheduling decisions, achieving low latency. If needed, scheduling-based resources provide backup reliability, but the preliminary configuration ensures that the low-latency path is always available
Data Source
AI summary
A user equipment (UE) selects first and second radio resources from respective first and second pools of radio resources. In one example these are primarily allocated for contention-free and scheduling-based channel access, respectively. Content to duplicate in parallel communications is selected based at least on a characteristic of uplink data waiting to be sent (such as size) and/or on the selected first and second radio resources (such as timing difference between them). The UE transmits the selected content on each of the selected first and second radio resources. In the examples the content to duplicate was selected from among the uplink data to send and a scheduling request message. In various embodiments one of these transmissions indicates it's a duplicate, and the duplicated scheduling request message is transmitted on the first resource with the uplink data. These teachings are particularly useful for URLLC data.