3 Definitions and abbreviations

06.313GPPDiscontinuous Transmission (DTX) for full rate speech traffic channelsTS

Abbreviations used in the present document are listed in GSM 01.04.

3.1 Definition of general terms

frame: time interval of 20 msec. corresponding to the time segmentation of the full rate speech transcoder (GSM 06.10), also used as a short term for a traffic frame.

traffic frame: block of 260 information bits (see GSM 05.03) transmitted on the full rate speech traffic channel.

(SID) silence descriptor frame: frame characterized by the SID code word. It conveys information on the acoustic background noise.

SID code word: fixed bit pattern defined in GSM 06.12, for labelling a traffic frame as a SID frame.

SID field: bit positions defined in GSM 06.12, of the SID codeword within a SID frame.

speech frame: traffic frame that cannot be classified as a SID frame.

3.2 Definition of terms on the receive side

bad traffic frame: traffic frame flagged BFI=1 (Bad Frame Indication) by the Radio Subsystem.

good traffic frame: traffic frame flagged BFI=0 by the Radio Subsystem.

good speech frame: good traffic frame which is not an accepted SID frame.

accepted SID frame: traffic frame in which the SID field deviates in less than 16 bit positions from the SID code word (flag SID=2 or SID=1).

valid SID frame: good traffic frame in which the SID field deviates in less than 2 bit positions from the SID code word (flag SID=2). This frame is valid for updating of comfort noise parameters at any time.

invalid SID frame: accepted SID frame with BFI=1, or accepted SID frame with BFI=0, in which the SID field deviates in more than 1 bit position from the SID code word (flag SID=1). This frame is not valid for updating comfort noise parameters, but the frame conveys information that comfort noise generations should be started or continued.

unusable frame: bad traffic frame that is not an accepted SID frame.

lost SID frame: unusable frame received when the RX DTX Handler is generating comfort noise and a SID frame is expected (Time Alignment Flag, TAF=1).

lost speech frame: unusable frame received when the RX DTX Handler is passing on traffic frames directly to the speech decoder.