06.813GPPDiscontinuous Transmission (DTX) for encanced full rate speech traffic channelsTS
For the purposes of the present document, the following terms and definitions apply:
accepted SID frame: traffic frame which is flagged with SID="1" or SID="2" by the Radio Subsystem.
bad traffic frame: traffic frame flagged BFI flag ="1" (Bad Frame Indication) by the Radio Subsystem.
frame: time interval of 20 msec. corresponding to the time segmentation of the Enhanced Full Rate speech transcoder (GSM 06.60 ), also used as a short term for a traffic frame.
good speech frame: good traffic frame which is not an accepted SID frame.
good traffic frame: traffic frame flagged BFI flag ="0" by the Radio Subsystem.
hangover period: period of 7 frames added at the end of a speech burst in which VAD flag ="0" and SP flag ="1".
invalid SID frame: accepted SID frame which was not classified as valid SID frame. This frame is not valid for updating comfort noise parameters, but the frame conveys information that comfort noise generations should be started or continued.
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.
SID code word: fixed bit pattern defined in GSM 06.62 , for labelling a traffic frame as a SID frame.
SID field: bit positions defined in GSM 06.62 , of the SID codeword within a SID frame.
SID frame: frame characterized by the SID (SIlence Descriptor) code word. It conveys information on the acoustic background noise.
SP flag: boolean flag, generated by the TX DTX handler, indicating the presence of a speech frame ("1") or the presence of a SID frame ("0").
speech frame: traffic frame that cannot be classified as a SID frame.
TAF flag: Time Alignment Flag. Boolean flag, marks with TAF=1 those traffic frames that are aligned with the SACCH multiframe structure (see GSM 05.08 ). The next SID frame is expected at the decoder when TAF=1.
traffic frame: block of 244 information bits transmitted on the Enhanced Full Rate speech traffic channel.
unusable frame: bad traffic frame that is not an accepted SID frame.
VAD flag: boolean flag, generated by the VAD algorithm defined in GSM 06.82  indicating the presence ("1") or the absence ("0") of a speech frame.
valid SID frame: good traffic frame flagged with SID="2" by the Radio Subsystem. This frame is valid for updating of comfort noise parameters at any time.
For the purposes of the present document, the following symbol applies:
Nelapsed Number of elapsed frames since the last updated SID frame.
For the purposes of the present document, the following abbreviations apply:
BFI Bad Frame Indicator
BSC Base Station Controller
BSS Base Station System
DTX Discontinuous Transmission
ETS European Telecommunication Standard
FACCH Fast Associated Control CHannel
GSM Global System for Mobile Telecommunications
MS Mobile Station
RSS Radio Sub System
SACCH Slow Associated Control CHannel
SID SIlence Descriptor
VAD Voice Activity Detector
For abbreviations not given in this clause, see GSM 01.04 .