UE Triggered Semi-Persistent Scheduling Activation for V2X Latency
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Solution Overview
Problem
Current semi-persistent scheduling (SPS) in LTE-based vehicle-to-everything (V2X) communication systems faces challenges in reducing latency for delay-critical data, such as decentralized environmental notification messages (DENM) or cooperative awareness messages (CAM), due to the gap between user data generation and SPS resource configuration.
Innovation Solution
The proposed method involves a user equipment (UE) triggered SPS activation, reactivation, and release mechanism, where the UE actively requests SPS activation when UL data is available, reducing the gap between data generation and SPS resource utilization. This is achieved through scheduling requests (SR) on the physical uplink control channel (PUCCH) or random access, allowing for timely SPS resource allocation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If SPS resource configuration is performed in advance, then resource allocation is simplified, but latency increases due to the gap between data generation and SPS activation
Solution Approach 1:
The patent implements dynamic SPS activation where the UE can request SPS activation via scheduling request (SR) when uplink data becomes available. This dynamic mechanism allows the system to adapt between static pre-configuration and on-demand activation, reducing latency for delay-critical V2X messages while maintaining simplified resource allocation through pre-configured SPS parameters.
2Loss of time
If SPS is activated closer to data generation time, then latency is reduced, but system complexity and overhead increase
Solution Approach 1:
The patent enables the UE to self-trigger SPS activation by monitoring its own uplink data buffer status and autonomously sending scheduling requests when data becomes available. This self-service mechanism reduces the need for continuous network control signaling while allowing timely SPS activation, thereby reducing latency without proportionally increasing system complexity.
3Reliability
If SPS is continuously maintained, then resource availability is ensured, but resource waste occurs for delay-insensitive data
Solution Approach 1:
The patent implements periodic SPS activation based on data availability rather than continuous maintenance. The SPS resource is activated periodically when the UE has uplink data to transmit, and can be released or deactivated when data transmission is complete. This periodic action ensures resource availability when needed while avoiding continuous resource allocation for delay-insensitive data, reducing resource waste.
Data Source
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AI summary
A method performed by a user equipment (UE) in a wireless communication system is proposed, which comprises: receiving, from a network, a radio resource control (RRC) release message comprising a resource configuration including i) information for at least one periodic uplink resource and ii) information for a validity duration during which a data transmission using the at least one periodic uplink resource is valid; suspending one or more radio bearers; resuming the one or more suspended radio bearers for the data transmission; and performing the data transmission using the at least one periodic resource to the network during the validity duration.