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P300H P300 Series Modem Installation and Operating Handbook Page 157
for the distant Eb/No and distant end Eb/No responses between M&C messages using the ESC
channel.
If the ESC interface is set to RS485, then the external RS485 interface will be disabled and the AUPC
will use 100% of the ESC channel bandwidth to achieve as high an Eb/No reporting rate as possible.
If the ESC interface is set to RS232 or RS422, AUPC cannot be used.
The Eb/No update rate and percentage of ESC channel bandwidth used is displayed on one screen of the
Info, View Config, Tx sequence of screen displays.
8.11.2 Configuring AUPC for operation
DO NOT switch on the AUPC immediately, it is much simpler to get the circuit working first, determine the
normal levels, AND THEN activate the AUPC.
Configure the modems at both ends of the link and ensure the basic satellite link is operating correctly.
Set the Tx power to achieve the distant Eb/No expected under clear sky conditions.
For IBS/SMS and IDR carriers the ESC can be switched on later within the overhead without
changing the carrier power or bandwidth.
For Closed Net Plus ESC carriers, the overhead is added as required for the ESC channel. Adding
an ESC channel later will change the bandwidth of the signal and may slightly affect the Eb/No.
In this case configure the ESC at least to a nominal Baud rate. If the ESC is not used for any other
M&C purposes then 300 Baud may be sufficient for AUPC alone.
Configure an ESC channel for 8 bits no parity, Baud rate as described below.
For IBS/SMS and IDR configure as higher rate ESC channel as the modem can provide. This will
give the fastest possible reporting rate.
For Closed Net Plus ESC our suggestion would be to include the optional Backward Alarm (as this
is a very useful feature), and set the Baud rates as high as possible without either exceeding the
allotted satellite bandwidth or using an overhead over 10%.
The ESC channel for the AUPC must have symmetrical Baud rates.
Set the ESC interface:
If the ESC channel is to be used for AUPC only, set the ESC interface to RS485. The external
RS485 port will be disabled and the AUPC will use 100% of the ESC channel capacity at whatever
Baud rate you have defined the ESC channel.
If the ESC channel is to be used for AUPC and distant end remote M&C, set the ESC interface to
either Link-Local or Link-Remote (Local at the controlling PC end, remote at the end farthest away
from the PC).
Note: This is contrary to expectations ! When using AUPC with either Link-Local and Link-
Remote selected as the ESC interface (to internally connect the Remote M&C port to the
ESC channel) it is not required to have the ESC channel at the same Baud rate as the
M&C system.
For example the station M&C could be running at 9600 Baud, and the ESC channel set
for 2400 Baud. The AUPC software will buffer and rate convert the M&C messages whilst
interleaving the AUPC data. M&C messages will of course take longer to get across a
2400 Baud ESC than a 9600 Baud ESC, but if the bandwidth has to be paid for (ie it’s not
withing the IBS/SMS or IDR overheads) then it’s worth the saving.
Alternatively if the station M&C is at say 2400 Baud, but the station is transmitting a
512kbps IBS/SMS link that would support a 19200 Baud ESC within the IBS/SMS
overhead. Setting the ESC for 19200 Baud will provide a very high update rate for the
Eb/No monitoring, by having enough bandwidth so that the maximum 33% it uses in this
mode can provide at least a 1Hz update rate.