Comtech EF Data CDM-570/570L Vipersat - Manual (Page 142)

Entry Channel Mode Switching
B-24 Vipersat CDM-570/570L User Guide
Entry Channel Mode Switching
Entry Channel Mode (ECM) provides a method for Remotes requiring SCPC
access channels to enter/re-enter the network, initially or after a power or other
site outage.
Two versions of Entry Channel Mode switching are used in Vipersat networks.
The version that is available for implementation in a Vipersat network will vary
depending on the satellite modem model that is deployed in the network.
STDMA ECM is currently available for CDM-570/L and SLM-5650A modems.
Dynamic ECM (ECMv2) is currently available for CDM-570/L modems and the
Advanced VSAT Series800 modems that include the CDM-800, CDM-840, and
CDD-880.
STDMA Entry Channel Mode
With STDMA Entry Channel Mode, the switch time will be variable based on
the burst rate (bps) of the STDMA group, the number of Remotes with slots in
the group, and where in the burst cycle the Remote is when it acknowledges
receipt of the burst map.
Initial SCPC rates are settable for each Remote in the STDMA group(s). Upon
detection of a burst map acknowledgement from a Remote, the STDMA burst
controller will send a switch request to the VMS with the operator-specified
initial SCPC rate. Upon determining that there is an available demodulator and
sufficient pool bandwidth, the VMS will send a multi-command to remove the
Remote from the STDMA group, tune it and the switched demodulator to the
specified initial bit rate and selected pool frequency. The Remote will stay at
this initial rate unless an application (such as VTC) or consistent load causes it
to request additional bandwidth from the VMS.
The initial switch from Entry Channel Mode to SCPC mode is not driven by the
presence or absence of customer traffic. Once in SCPC mode, the switched
initial data rate becomes the new temporary home state. This temporary home
state sets the low limit data load threshold, where the Remote will stop sending
load switch request commands. ECM Remotes in SCPC mode do not require
burst maps to maintain SCPC transmission.
Note: Remotes operating in ECM toggle directly from STDMA to SCPC.
The initial SCPC switch state is used instead of the modem’s
internal Home State.
After the ECM Remotes are processed into SCPC, the burst controller drops
into sanity mode, sending a keep alive map to service Remotes which may have
NOTE