Entry Channel - Comtech EF Data Vipersat SLM-5650A User Manual

V i p e r s a t C o nf i g u r a t i o n
been assigned slots, the burst map is checked to see if the total cycle length
exceeds one second. If not, then all requirements are satisfied and the burst map
is complete. However, if the cycle is greater than one second, then the slots are
adjusted proportionally so that all Remotes receive at least their guaranteed rate
plus whatever excess is still available.
GIR mode allows guaranteed information rates to be set for each Remote in the
group. When the one second restriction is exceeded, Remotes without a speci-
fied GIR are reduced to the global minimum slot size and the remaining band-
width is distributed to Remotes that have been assigned a GIR rate, thus
ensuring additional bandwidth to these units when needed.
Note: GIR allocations are restricted so that assigned GIR totals cannot exceed
NOTE
The GIR setting for each Remote is specified using the STDMA Remote Poli-
cies screen (refer to the section "ECM Remotes" on page 3-25). 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, Load switching must be Enabled on this
Hub unit, and corresponding Remote modems must be configured with Load
switching Enabled as well. 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
Load switching feature must be Enabled on this Hub unit, and switching poli-
cies for the Remotes must be configured (refer to the section "ECM Remotes"
on page 3-25). Corresponding Remote modems must be configured with Load
switching Enabled. Note that the settings for Step Up and Step Down Threshold
values should be adjusted as necessary for the application.
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
3-16
the available bandwidth. This ensures proper bandwidth allocation when
the network is overloaded.
V i p e r s a t S L M - 5 6 5 0 A U s e r G u i d e