Dynamic SPS Scheduling for UU-Based V2V CAM Latency
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Solution Overview
Problem
Existing vehicular communication systems face challenges in meeting the high reliability and low latency requirements of public safety applications, particularly in areas without network coverage, due to inefficiencies in semi-persistent scheduling (SPS) for periodic messages like CAM, leading to resource wastage and increased latency.
Innovation Solution
The proposed solution involves a WTRU requesting and configuring semi-persistent scheduling (SPS) parameters, including periodicity and offset adjustments, through RRC signaling and MAC control elements, to align SPS resources with the generation pattern of CAM messages, allowing dynamic changes in periodicity and offset to meet latency and reliability demands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If semi-persistent scheduling (SPS) is used for periodic CAM messages, then resource allocation is simplified and overhead is reduced, but resource utilization efficiency deteriorates and latency increases due to fixed periodicity not matching actual message generation patterns
Solution Approach 1:
The patent applies dynamics by enabling the WTRU to request and adjust SPS periodicity values dynamically based on actual CAM message generation patterns. The periodicity is no longer fixed but can be changed through WTRU requests and network confirmation, allowing the system to adapt to varying traffic conditions while maintaining the simplified SPS framework.
Solution Approach 2:
The patent changes the periodicity parameter of SPS from a fixed value to an adjustable value. The WTRU monitors its CAM message generation pattern and requests periodicity changes when the actual pattern differs from the configured SPS periodicity. This parameter adjustment resolves the mismatch between fixed SPS timing and variable message generation patterns.
2Loss of energy
If semi-persistent scheduling (SPS) with fixed periodicity is used, then scheduling overhead is reduced, but latency increases when SPS periodicity does not align with CAM message generation intervals
Solution Approach 1:
The patent implements feedback by having the WTRU monitor its actual CAM message generation pattern and compare it with the configured SPS periodicity. When a mismatch is detected, the WTRU sends a request to adjust the periodicity. This closed-loop feedback mechanism ensures that SPS timing remains aligned with actual traffic patterns, minimizing latency while keeping overhead low.
Solution Approach 2:
The patent applies preliminary action by having the WTRU proactively request periodicity adjustments before latency issues become critical. The WTRU monitors the alignment between SPS periodicity and message generation patterns continuously and initiates adjustment requests in advance, ensuring timely realignment and preventing excessive latency accumulation.
3Device complexity
If SPS resources are allocated based on fixed periodicity, then resource allocation is simplified, but resource wastage increases when actual message generation pattern differs from SPS periodicity
Solution Approach 1:
The patent makes resource allocation dynamic by allowing the WTRU to request changes in SPS periodicity based on actual traffic patterns. Instead of static resource allocation, the system now adapts resource timing to match actual CAM message generation intervals, reducing resource wastage while maintaining allocation simplicity through the established SPS framework.
Solution Approach 2:
The patent enables self-service by allowing the WTRU to autonomously monitor its own traffic patterns and initiate requests for SPS parameter adjustments. The WTRU independently determines when resource allocation mismatches occur and triggers the necessary reconfiguration process, reducing the need for complex network-side monitoring while minimizing resource wastage.
Data Source
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AI summary
A method for operation in a WTRU may comprise transmitting, from the WTRU to an eNB, a request for SPS resources including a periodicity of the requested SPS resources and a time offset indicative of a time in which the WTRU expects have an SPS resource allocated. The method may further comprise receiving, by the WTRU from the eNB, in response to the transmitted request for SPS resources, an SPS configuration. The time offset of the transmitted request may include a subframe number (SFN) offset with respect to SFN 0 of the WTRU. The received SPS configuration may correspond to a PC5 interface and the SPS configuration may be received over a physical downlink control channel (PDCCH).