Semi-Persistent Scheduling Resource Alignment for URLLC Latency
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Solution Overview
Problem
In wireless communication networks, especially for Ultra Reliable and Low Latency Communication (URLLC) in 5G, there is a challenge in aligning the periodicity and starting time of critical data transmissions with allocated Semi-persistent Scheduling (SPS) resources, leading to misalignment and increased latency or inefficiency in resource utilization.
Innovation Solution
The base station over-provisions SPS resources and recursively adjusts the SPS configuration based on the timing of data transmissions to synchronize the SPS period with the periodic data transmission, allowing the UE to skip transmissions when the buffer is empty, and uses techniques like transport block repetition and cyclic shifts for padding detection to align packet arrival times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the base station allocates fixed periodic SPS resources to the UE, then resource utilization efficiency is improved, but misalignment between packet arrival time and allocated resources increases latency
Solution Approach 1:
The patent applies dynamics by making the SPS configuration adjustable and adaptive. The base station can modify SPS parameters (periodicity, offset, resource allocation) based on observed packet arrival patterns. This transforms the static fixed allocation into a dynamic system that evolves to match actual traffic characteristics, resolving the contradiction between fixed resource efficiency and adaptive latency reduction.
Solution Approach 2:
The patent implements feedback mechanisms where the base station monitors packet arrival times and uses this information to recursively adjust SPS configurations. The system observes the timing of uplink data transmissions and refines the SPS offset and periodicity accordingly. This closed-loop feedback enables the system to align allocated resources with actual packet arrival patterns, reducing latency while maintaining resource efficiency.
2Reliability
If the base station over-provisions SPS resources to ensure coverage, then reliability of data transmission is improved, but resource waste increases when buffer is empty
Solution Approach 1:
The patent applies partial action by allocating SPS resources that exceed the minimum single-transmission requirement but are optimized based on observed packet arrivals. Rather than allocating resources for every possible scenario (excessive), the system provisions a moderate amount (partial) and adjusts based on actual needs. The base station can configure multiple SPS configurations with different resource allocations and switch between them based on traffic patterns, ensuring sufficient resources for reliability while avoiding constant waste.
Solution Approach 2:
The patent uses parameter changes by adjusting SPS configuration parameters (resource block allocation, periodicity, offset) based on observed traffic patterns. When packets arrive frequently, the system maintains higher resource allocation for reliability. When traffic is sparse, the system reduces resource allocation to minimize waste. This dynamic parameter adjustment resolves the contradiction between maintaining sufficient resources for reliability and reducing waste during low-traffic periods.
3Ease of operation
If the UE transmits padding on allocated SPS resources when buffer is empty, then resource allocation simplicity is maintained, but unnecessary interference is introduced
Solution Approach 1:
The patent extracts the harmful padding transmission action from the system. Instead of requiring UEs to transmit padding on all allocated SPS resources, the patent enables UEs to skip transmission when the buffer is empty. This removes the source of unnecessary interference while maintaining the simplicity of pre-configured SPS resources. The base station simply needs to configure the SPS resources and allow UEs to transmit only when data is available.
4Adaptability or versatility
If the base station uses dynamic scheduling for each UL resource allocation, then adaptability to varying traffic patterns is improved, but PDCCH load and signaling overhead increase
Solution Approach 1:
The patent applies periodic action by using Semi-Persistent Scheduling where resources are allocated periodically based on pre-configured SPS parameters rather than through continuous dynamic scheduling. The base station configures SPS with specific periodicity and offset values that match the periodic nature of many URLLC traffic patterns (e.g., sensor data every 5ms). This periodic allocation dramatically reduces PDCCH load compared to dynamic scheduling while maintaining adaptability through the ability to adjust SPS parameters based on observed traffic.
Data Source
AI summary
The present disclosure provides techniques for reducing latency of periodic URLLC transmission and other critical data transmission with low latency requirements. To support periodic URLLC traffic, SPS with repetition is used. Before synchronization is achieved, the base station sends to the UE an SPS configuration for a periodic uplink data transmission. When the starting time of the data transmission is not known, the base station over-provisions SPS resources for the periodic data transmission. Based on the timing of the data transmissions, the base station adjusts the timing of the SPS configuration.