User guide

Vipersat Configuration
3-10 Vipersat CDM-570/570L User Guide
Hub Type
This menu item is only displayed if the CDM-570/570L is being used as a Hub
in the network, and provides the functionality for the STDMA Burst Controller.
Vipersat STDMA has five 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.
The Hub can be configured to operate as one of the five 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.
1 – Fixed
In the Fixed mode, all remotes have the same data slot size regardless of type of
traffic or load. This mode minimizes the amount of jitter between remote trans-
mission times, and is useful for tuning STDMA as well as for troubleshooting
purposes.