Sidelink Relay Discovery Signaling for Low-Latency V2X Matching
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Solution Overview
Problem
The existing PC5-U protocol in 3GPP R17 lacks dedicated sidelink (SL) communication for relay discovery in vehicle-to-everything (V2X), leading to significant delays due to SD-RSRP measurement in the relay discovery process.
Innovation Solution
Incorporating a first identifier in the SCI to indicate a discovery message at the PHY layer and using dedicated resources for discovery messages, allowing early identification of relay terminal devices, thereby reducing delays and enabling capability matching between terminal devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If relay discovery is implemented by using existing PC5-U protocol, then backward compatibility is maintained, but large delay is caused due to SD-RSRP measurement
Solution Approach 1:
The patent applies preliminary action by performing capability indication during the relay discovery phase itself, rather than waiting until after discovery is complete. The remote UE includes its capability information (SD-RSRP measurement capability, relay selection capability) in the discovery message exchanged with the relay UE. This allows the relay UE to identify suitable relays based on capabilities before relay selection begins, eliminating the delay of performing SD-RSRP measurement after discovery.
2Device complexity
If discovery message identification is performed at MAC layer only, then protocol simplicity is maintained, but large delay is caused due to late message identification
Solution Approach 1:
The patent applies segmentation by dividing the capability indication function across multiple protocol layers. The MAC layer maintains its original function of transmitting discovery messages, while the PHY layer is enhanced to identify discovery messages through specific signal characteristics or preamble sequences. This segmentation allows early identification at PHY layer without requiring complete reconfiguration of the MAC layer, thus reducing delay while maintaining protocol structure.
3Reliability
If capability matching is performed after relay discovery, then relay selection accuracy is improved, but overall process time is increased
Solution Approach 1:
The patent merges the capability indication process with the relay discovery process. The remote UE includes capability information (SD-RSRP measurement capability, relay selection capability) directly in the discovery message exchanged during relay discovery. This merging allows the relay UE to perform capability-based filtering and identification during discovery itself, rather than as a separate post-discovery step. The result is that relay selection accuracy is maintained while overall process time is reduced, as capability matching occurs concurrently with discovery rather than sequentially after it.
Data Source
AI summary
Embodiments of this application provide example communication methods, apparatuses, and systems. One example method includes receiving, by a first terminal device, a first message from a second terminal device. The first message is determined to be a discovery message by the first terminal device based on a first resource for transmitting the first message, where the first resource is a resource specially used to transmit the discovery message, and the discovery message indicates that the second terminal device is a relay terminal device.