Padding Support; Vcm Guard Mode - Advantech SBD75e Series Installation And Operation Manual

Figure 4.33: Advanced Functions Main Window
4.9.3.1

Padding Support

The DVB-S2 specification provides for the use of padding to achieve certain link operation goals.
Unfortunately, the use of padding makes the link behaviour very vulnerable to un-correctable
transmission errors.
By default, padding support is disabled. In this case, the field of the base-band header, which is
used to implement padding (DFL), is ignored.
If, despite the serious system issues engendered by the use of padding support, it is still required,
the Padding Support box on the advanced window may be checked.
Note
The padding support control applies to all streams.
4.9.3.2

VCM Guard Mode

The DVB-S2 specification makes allowance for the concentration of multiple base-band streams,
to be transmitted using a variety of modulation and coding modes. Unfortunately, the robustness
of the stream concentration mechanism is very low when subjected to un-correctable
transmission errors.
By default, VCM guard mode is disabled. In this case, all received base-band frames, including
those with un-correctable transmission errors, are forwarded for stream de-concentration.
The VCM Guard Mode may be enabled by checking the VCM Guard Mode box on the
advanced window.
When VCM guard mode is engaged, all received base-band frames containing un-correctable
transmission errors are discarded.
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