Comtech EF Data CDD-56X Series Vipersat - Manual (Page 52)

Vipersat Configuration MN/22137, rev 1
3-18 Vipersat CDD-56X Series User Guide
CDD-56X based on the STDMA transmit bit rate as shown in the menu
in figure 3-7.
Slot Preamble Length
This menu item, which appears in all Hub and Remote configurations, displays
the current Slot Preamble size in milliseconds and bytes for the remotes in the
group. The Slot Preamble is the period between when the remote begins to
transmit (sends an ACK) to the Hub and when the first data packet is sent. This
allows time for signal lock to occur before data is sent, thus preventing data
loss. Higher data rates allow for a shorter preamble, since it is easier to achieve
signal lock. The setting for this parameter should be obtained using the Vipersat
STDMA Calculator.
Tip: For a copy of the latest Viper Calculator, contact a Comtech Vipersat
Networks representative.
Note: When either the BFAT feature is enabled or the Hub Type is ECMv2, the
preamble length is set automatically for the unit.
On a Hub unit, entering a P at the command prompt allows changing the pream-
ble duration in milliseconds.
Figure 3-17 Slot Preamble Length prompt
Slot Data Length
This menu item, which appears for Fixed, Entry Channel, and ECMv2 Hub
types, displays the current Slot Data Length in milliseconds and bytes for the
remotes in the group, and represents the amount of data that can be transmitted
or received in one spin of the STDMA cycle by each of the remotes belonging
to that group. This is the amount of time that the remote is provided to send data
in the cycle.
To change this setting, enter B at the command prompt to display the dialog
shown in figure 3-18.
NOTE