NR RACH MSG2 Resource Selection for Low-Overhead C-V2X Access
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Solution Overview
Problem
Existing wireless communication systems, particularly in 5G NR, face challenges in efficiently managing access procedures and reducing overhead in cellular vehicle-to-everything (CV2X) communications due to complications arising from beamforming and the need for improved coordination in resource allocation, especially in non-line-of-sight scenarios.
Innovation Solution
A method is introduced for selecting and transmitting a second Random Access Channel (RACH) message based on a RACH preamble, utilizing preconfigured discovery resources to reduce collisions and overhead by limiting unnecessary transmissions and beamforming, thereby optimizing resource usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If beamforming is used in 5G NR for CV2X communications, then communication reliability and signal quality are improved, but access procedure complexity and overhead increase due to beam management requirements
Solution Approach 1:
The access procedure is divided into distinct phases: a first phase for beam indication where the UE indicates the selected downlink beam, and a second phase for actual data transmission. This segmentation allows the system to manage beamforming complexity by handling beam selection separately from data communication, reducing the overhead in the access procedure while maintaining communication reliability.
Solution Approach 2:
The system performs preliminary beam indication and selection before the actual data transmission begins. The UE indicates its selected downlink beam during the random access procedure, and the gNB uses this information to configure subsequent transmissions. This preliminary action avoids the need for continuous beam management during data transmission, reducing procedural complexity.
2Productivity
If traditional RACH procedure is used in 5G NR, then access procedure is standardized, but resource usage and overhead are excessive due to unnecessary beamforming operations
Solution Approach 1:
The invention extracts and removes unnecessary beamforming operations from the traditional RACH procedure. Specifically, the full beam sweeping and multiple beam transmissions are eliminated in favor of a simplified approach where the UE indicates its selected beam and the gNB transmits only on that indicated beam, significantly reducing resource usage and energy consumption while maintaining access procedure functionality.
Solution Approach 2:
Instead of performing complete beam sweeping and evaluating all possible beams (excessive action), the system uses a partial approach where the UE indicates its preferred beam based on prior measurements or preferences, and the gNB proceeds with transmission only on that selected beam. This partial action reduces the number of transmissions required while achieving sufficient access procedure objectives.
3Reliability
If multiple beam transmissions are performed for RAR, then coverage and reliability are improved, but collision probability and overhead increase in non-line-of-sight scenarios
Solution Approach 1:
The system transitions from uniform beam transmission to localized beam transmission based on UE indication. Instead of transmitting RAR on multiple beams regardless of UE position, the gNB identifies the specific downlink beam indicated by the UE and transmits only on that beam. This local quality approach reduces collisions in non-line-of-sight scenarios while maintaining coverage through the indicated beam direction.
Data Source
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AI summary
Methods, apparatuses, and computer-readable mediums for wireless communication are disclosed by the present disclosure. In an example, the present disclosure includes receiving, at a second device, a Random Access Channel (RACH) preamble from a first device, the RACH preamble initiates an access procedure between the first device and the second device; selecting, by the second device, a transmission resource associated with a second RACH message based on the RACH preamble; and transmitting, by the second device, the second RACH message on the selected transmission resource to the first device.