06.913GPPSubstitution and muting of lost frames for AMR speech traffic channelsTS
For the purposes of the present document, the following terms and definitions apply.
N-point median operation: Consists of sorting the N elements belonging to the set for which the median operation is to be performed in an ascending order according to their values, and selecting the (int (N/2) + 1) -the largest value of the sorted set as the median value.
Further definitions of terms used in the present document can be found in GSM 06.90 , GSM 06.93 , GSM 05.03  and GSM 08.60 .
For the purposes of the present document, the following abbreviations apply:
BFI Bad Frame Indication from Radio Sub System
BSI_Abis Bad Sub-block Indication obtained from A-bis CRC checks
prevBFI Bad Frame Indication of previous frame
PDFI Potentially Degraded Frame Indication from RSS
RSS Radio Sub System
DTX Discontinuous Transmission
SID SIlence Descriptor frame (Background descriptor)
CRC Cyclic Redundancy Check
CCU Channel Coding Unit
ECU Error Concealment Unit
BFH Bad Frame Handling
medianN N-point median operation
TRAU Transcoding Rate Adaptation Unit