BFD

Technical Explanation

A UE monitors periodic Beam Failure Detection (BFD) reference signals (SSB or periodic CSI-RS). If the estimated radio link quality across all serving beams falls below the hypothetical out-of-sync threshold Qout consecutively, the physical layer sends a 'beam failure indication' to the MAC layer. When counter BFI_COUNTER reaches max limit, beam failure is declared.

Key Functions

• Monitors serving beam radio quality against block error threshold Qout
• Maintains MAC counter BFI_COUNTER tracking consecutive failed indications
• Declares beam failure when all serving spatial links degrade