Comtech EF Data CDD-56X Series Vipersat - Manual (Page 44)

Vipersat Configuration MN/22137, rev 1
3-10 Vipersat CDD-56X Series User Guide
STDMA Tx Rate
This menu item shows the STDMA Transmit Rate (in bps) of data that the
CDD-56X receives. This item is read-only and cannot be modified in this menu.
Hub Type
This menu item is only displayed if the CDD-56X is being used as a Hub in the
network, and provides the functionality for the STDMA Burst Controller.
Vipersat STDMA has six modes of operation:
• Fixed — all remotes get the same data slot time (slot size) in the cycle,
regardless of activity. Cycle time is fixed also.
• Dynamic Slot — data slot time of remotes vary according to activity,
cycle time does not.
• Dynamic Cycle — slot time and cycle time vary according to activity of
remotes.
• GIR (Guaranteed Information Rate) — each remote always has at least the
minimum data slot size when needed, and cycle time is variable up to a
maximum of one second.
• Entry Channel — remotes run in SCPC mode, but STDMA is used for
maintenance and control channel.
• ECMv2 — utilizes a modified slotted Aloha method for remotes to
establish registration in the network and obtain the means for switching
into SCPC mode.
The Hub can be configured to operate as one of the six types by entering a T at
the command prompt to display the dialog shown in figure 3-9.
Figure 3-9 Hub Type prompt
This selection determines whether available bandwidth will be a static (fixed)
assignment, or whether bandwidth allocation will be dynamic with automatic
switching to dynamically optimize bandwidth utilization.