Reference Manual

Speech and Data Services
In order to deactivate speech coding/decoding in the RTC, the RBS
issues TRAU frames of type Idle Pattern according to /GSM:08.61/.
During the exchange of TRAU frames between RBS and RTC carrying
half rate speech, the RBS regularly calculates an appropriate time
alignment value for controlling the downlink frame timing. This value
is included in the transmitted TRAU frames.
The TRAU frames exchanged between RBS and RTC during an active
call are of the following types:
•
Speech
• Speech containing coded silence information (used by function
DTX).
Half Rate Speech is either terminated by the RF Channel Release
function, or the Mode Modify function when Data or Signalling
services are requested.
18.3.5 Full Rate Data
Full rate data is either initiated by the Channel Activation function or
the Mode Modify function.
In order to activate and control rate adaptation of data in the RTC, the
RBS issues TRAU frames of type Data and channel type Full Rate.
In order to deactivate rate adaptation of data in the RTC, the RBS
issues TRAU frames of type Idle Speech and channel type Full Rate,
according to /GSM:08.60/.
The rate adaptation is split up between RTC and RBS and is performed
as described in /GSM:08.20/ and /GSM:08.60/.
The TRAU frames exchanged between RBS and RTC during an active
call can be of the following types:
•
Data
•
Data, containing Idle Data
The arrival of data blocks from the air interface is supervised by the
RBS.
If no data block is received, it is replaced by an idle data block.
Full Rate Data is either terminated by the RF Channel Release function,
or the Mode Modify function when Speech or Signalling services are
requested.
18.3.6 Half Rate Data
Full Rate Data is either initiated by the Channel Activation function or
the Mode Modify function.
In order to activate and control rate adaptation of data in the RTC, the
RBS issues TRAU frames opf type Data.
In order to deactivate rate adaptation of data in the RTC, the RBS
issues TRAU frames of type Idle Speech according to /GSM:08.61/.
The rate adaptation is split up between RTC and RBS and is performed
as described in /GSM:08.20/ and /GSM:08.61/.
EN/LZT 720 0008 R1A
2001-06-26
183 (421)
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