Beam Failure Recovery via MAC CE Beam Index Feedback
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Solution Overview
Problem
In the 5G New Radio (NR) system, existing beam failure recovery (BFR) methods face delays in the random access process, especially when the network device does not configure BFR Config, leading to inefficiencies in determining the correct beam for recovery.
Innovation Solution
A method where a terminal device sends a MAC control element (CE) indicating a beam index for feedback, allowing the network device to send a feedback message based on this index, enabling the terminal device to determine the success of beam failure recovery and potentially resending the MAC CE or initiating a random access process if recovery fails.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the network device does not configure BFR Config, then the terminal device must use the random access process for beam failure recovery, but this causes delays in the recovery process
Solution Approach 1:
The network device pre-configures multiple downlink beams and their corresponding beam indices before beam failure occurs. When beam failure is detected, the terminal device can immediately use the pre-configured beam indices to identify alternative beams without waiting for random access procedures, thereby reducing recovery delay while maintaining reliability
Solution Approach 2:
The terminal device sends a MAC CE feedback message containing the selected beam index to the network device. The network device uses this feedback to determine which beam the terminal has selected for recovery, enabling timely confirmation and reducing the overall recovery time while ensuring reliable beam selection
2Reliability
If the terminal device uses the random access process for beam failure recovery, then recovery can be achieved, but the process becomes inefficient and delayed
Solution Approach 1:
The network device configures the terminal with multiple downlink beam indices in advance through RRC signaling. When beam failure occurs, the terminal can immediately evaluate pre-configured beams and send a MAC CE indicating the selected beam index, bypassing the lengthy random access process and significantly improving recovery efficiency while maintaining reliable beam selection capability
Solution Approach 2:
The terminal device autonomously evaluates the quality of pre-configured downlink beams using reference signals and independently selects the best beam for recovery. The terminal sends a MAC CE with the selected beam index without requiring network device intervention in the beam selection process, thereby improving recovery efficiency while ensuring reliable connection restoration
Data Source
AI summary
Disclosed by the present invention is a method for indicating beam failure recovery, comprising: when conditions for triggering beam failure recovery are met, a terminal device sending a media access control (MAC) control element (CE), the MAC CE indicating a beam index corresponding to a beam used by a network device to send a feedback message. Further disclosed by the present invention are another method for indicating beam failure recovery, a terminal device, a network device, and a storage medium.