DTX
: Discontinuous
Transmission
When an MS is engaged but no speech
signals are transferred, the MS sends only comfort noises periodically to the
peer end. The data volume of these comfort noises is smaller than the volume of
normal speech data.
An MS does not keep transmitting speech
signals during a call. Typically, only 40% of the duration of the call is occupied
for speech transmission. During the non-speech transmission period, an MS
reduces the transmitted data to suppress the interference to other channels and
to help reserve system resources. In addition, DTX relieves the workload of the
TX module of the MS. The MS can enjoy a longer call duration and standby time.
DTX affects only the transmission of TCH frames.
DTX can reduce the transmit power of an
MS when the MS does not receive any speech signals.
The quality of speech services in the
entire radio network is thus improved.
DTX involves the following technical
aspects:
·
Silence
Descriptor (SID) frames
·
Voice
Activity Detection (VAD)
·
Global measurement and local
measurement
When there is no speech signal
transmission during a call, the MS sends SID frames to the BTS.
The VAD enables the MS to accurately
detect speech signals
DRX
: Discontinuous Reception
An MS in idle mode detects only the
paging channels within a specific paging group. When other paging groups send
paging messages to an MS, the MS blocks the receive channel.
Each MS is mapped to a paging group,
and each paging group is mapped to a paging subchannel in the serving cell.
When operating in idle mode, an MS detects the paging messages broadcast by the
system only on the mapped paging sub-channel. The MS blocks other paging
sub-channels by powering off some hardware of the MS, and this also saves power.