Q-Flex Satellite Modem Installation and Operating Handbook
6-65
DVB-S2
QPSK: 1/4, 1/3, 2/5, 1/2, 3/5, 2/3, 3/4, 4/5, 5/6, 8/9, 9/10
8PSK: 3/5, 2/3, 3/4, 5/6, 8/9, 9/10
16APSK: 2/3, 3/4, 4/5, 5/6, 8/9, 9/10
32APSK: 3/4, 4/5, 5/6, 8/9, 9/10
Table 6-71 Tx Modulation and FEC Code Rates
6.2.3.15 Stream Tx FEC Code Rate
Each stream can use any of the supported DVB-S2 FEC code rates listed in
Table 6-58
.
(In receive, the FEC code rate is detected automatically.)
6.2.3.16 Stream Tx Pilot Tones
Pilots are an On/Off control that controls whether DVB-S2 pilots, which are unmodulated
symbols, are injected into the carrier on a regular basis in order to help the demodulator
lock onto the carrier. The pilots are 36 symbols long and are injected every 1440
symbols, representing an additional overhead of around 2.4%.
6.2.3.17 DVB-S2 Tx 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.
Table 6-72 DVB-S2 Tx/Rx Frame Size
6.2.3.18 Tx/Rx Symbol Rate
The calculated transmit and receive symbol rates, aggregated for all streams, are
displayed in order to allow the user to verify that the streams have been set up correctly.
6.2.4 Edit->IP->QoS Screen
Traffic shaping is described in
Section 7.8.9