Comtech EF Data CDD-56X Series Vipersat - Manual (Page 46)

Vipersat Configuration MN/22137, rev 1
3-12 Vipersat CDD-56X Series User Guide
Note: GIR allocations are restricted so that assigned GIR totals cannot exceed
the available bandwidth. This ensures proper bandwidth allocation when
the network is overloaded.
The GIR setting for each Remote is specified using the STDMA Remote Poli-
cies screen (refer to the section “Set Remote Policies” on page 3-24). When
combined with Auto switching, GIR allows trigger points to be set where the
Remote will jump out into SCPC mode. This is done using the Load Switch
setting. Note that, for this function, Auto switching must be Enabled on this
Hub unit, and corresponding Remote modems must be configured with Auto
switching and Load switching Enabled. Also, the settings for Step Up and Step
Down Threshold values should be adjusted as necessary for the application.
5 – Entry Channel
The Entry Channel mode provides remotes in the group with a shared channel
in which they can gain initial access to the network. Since very small STDMA
data rates are required in this configuration, a larger number of remotes can
share the cycle. As soon as the Hub receives an STDMA ACK from the
Remote, it initiates an immediate switch to SCPC mode based on the policy set
for that Remote. Note that the switch occurs as soon as the Hub receives an
ACK even though there may not be traffic at that time. The persistence of the
link will be determined by the unit’s flag settings.
When choosing Entry Channel as the Hub type for the STDMA Controller, the
Auto switching feature must be Enabled on this Hub unit, and switching policies
for the remotes must be configured (refer to the section “Set Remote Policies”
on page 3-24). Corresponding Remote modems must be configured with Auto
switching and Load switching Enabled. Note that the settings for Step Up and
Step Down Threshold values should be adjusted as necessary for the applica-
tion.
This mode is designed to accommodate the needs of a Remote that will not be
continuously connected to the network, but which has the need to be able to
make an on-demand connection when required, such as in a mobile application.
In the event of a power outage, Entry Channel provides a bandwidth-efficient
method for remotes with low latency requirements to re-enter the network once
power is restored.
6 – ECMv2
The ECMv2 (Dynamic Entry Channel) mode is very similar to the regular
Entry Channel mode. However, the associated limitation in the number of
Remotes is eliminated via the modified slotted Aloha method that is utilized for
this mode. No cycle is used, and a Remote List is not necessary.
The Hub broadcasts an anouncement message to all Remotes that are tuned to
receive it that provides the available slots and the tuning parameters for trans-
NOTE