User guide

Appendix G - Entry Channel Mode Switching G-1
A PPENDIX
ENTRY CHANNEL MODE SWITCHING
Entry Channel Mode (ECM)
STDMA entry channel mode provides a method for remotes requiring SCPC
access channels to enter/re-enter the network initially or after a power or other
site outage. 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
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 cause it to request
additional bandwidth from the VMS.
Entry channel mode is not driven by the presence or absence of customer traffic.
Once in ECM 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. Remotes in
ECM mode do not require burst maps to maintain SCPC transmission.
Note: Remotes in ECM mode toggle directly from STDMA to SCPC and back.
The initial SCPC switch state is used instead of the modem’s internal
home state for modems operating in ECM mode.
NOTE