Discontinuous Transmission
/GSM:06.42/ Voice Activity Detection (half rate speech)
/GSM:06.81/ Overall DTX Operation (enhanced full
rate speech)
The downlink DTX function is supported for channel modes:
•
TCH speech, full rate (GSM speech alg. version 1), uni-directional
•
TCH speech, full rate (Speech full rate version 2), uni-directional
•
TCH speech, full rate (GSM speech alg. version 1), bi-directional
•
TCH speech, full rate (Speech full rate version 2), bi-directional
• TCH speech, half rate
•
TCH data, 14.4 kbit/s, non-transparent, uni-directional
• TCH data, 9.6 kbit/s, non-transparent, uni-directional
•
TCH data, 4.8 kbit/s, non-transparent (Only half rate supported)
• TCH data, 14.4 kbit/s, non-transparent, bi-directional
•
TCH data, 9.6 kbit/s, non-transparent, bi-directional
For all other Channel Modes, the DTXd indicator is ignored, since the
DTX function is not applicable.
Channel combinations supported /GSM:05.02:6.4/:
•
(i) TCH/F + FACCH/F + SACCH/TF
• (ii) TCH/H(0,1) + FACCH/H(0,1) + SACCH/TH(0,1)
•
(viii) TCH/F + FACCH/F + SACCH/M
• (ix) TCH/F + SACCH/M
• (x) TCH/FD + SACCH/MD
The downlink DTX function is enabled when a
CHANNEL_ACTIVATION message, or a MODE_MODIFY message
with the DTX downlink indicator set, is received from the BSC.
The downlink DTX function for speech is initiated when a speech
frame containing comfort noise parameters, is received from the RTC
(Remote Transcoder).
The downlink DTX function for non-transparent data is initiated when a
complete RLP (Radio Link Protocol) frame, with all E1-bits /
GSM:04.21/ set to 1, is received from the RTC.
DTX Handling Speech
The usage of downlink DTX (ON/OFF) is indicated (as a flag) in the
full rate RTH-SPEECH-IND/RTH-E-SPEECH-IND, half rate RTH-
SPEECH-IND and RTH- IDLE SPEECH-IND frames to the RTC. To
detect if a full rate RTH-SPEECH-IND/RTH-E-SPEECH-IND or half
rate RTH-SPEECH-IND frame (received from the RTC) contains
speech or comfort noise parameters /GSM:06.32 / or /GSM:06.42/, RBS
analyses the SID code word /GSM:06.12:5.2/, /GSM:06.62:5.3/ or /
GSM:06.22:5.3/.
286 (485)
EN/LZT 720 0008 P2A
2001-11-28
© Ericsson Radio Systems AB
— All Rights Reserved —
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