Q-Lite Satellite Modem Installation and Operating Handbook
6-20
6.2.5.3 DVB-S2/S2X Tx/Rx Frame Size
Short
This represents a frame size of 16,200 bits per frame.
Normal
This represents a frame size of 64,800 bits per frame. This is more
bandwidth efficient than short frames but has four times the
latency. As a guideline, short frames have a latency of around
25ms at 1Mbps, whereas the latency for normal frames is around
100ms at 1Mbps. The latency will halve as data rate doubles.
Very short
This represents a frame size of 5,400 bits, reducing latency to 33%
of the standard DVB-S2 Short frame.
Ultra short
This represents a frame size of 3,240 bits, reducing latency to 20%
of the standard DVB-S2 Short frame.
Table 6-17 DVB-S2/S2X Tx/Rx Frame Size
6.2.5.4 Sweep Mode
Normal
In this mode the sweep width is controlled automatically by the
modem. The default sweep width used by the modem is +/-20kHz.
Other
This mode allows the user to set the sweep width in order to
compensate for carrier frequency uncertainty introduced in either
the ground equipment or in the space segment (due to, for
example, frequency conversion errors). At very low data rates,
reducing the sweep width may speed up carrier acquisition.
Table 6-18 Sweep Mode
6.2.5.5 Sweep Width
Range (+/-):
1kHz to 250kHz; step size: 1kHz
Description:
Controls the Rx signal sweep width when the
Sweep mode
is set to
Other
.
This is a +/- setting, i.e. the total width is twice the value that is entered.
The default sweep width used by the modem is +/-20kHz.
Table 6-19 Sweep Width
6.2.5.6 Acknowledge Power Break
If the
Modem carrier
setting on the
Edit->Tx-Rx->Service
menu is set to ‘
On (mute if
power break)’
the any power outage must be explicitly acknowledged using this control
thereby confirming that it is okay to restart transmission following the outage.
