Available Baud Rates; Configuration; Effect On Eb/No Performance - Comtech EF Data CDM-625 Installation And Operation Manual

CDM-625 Advanced Satellite Modem
ESC++

12.3 Available Baud Rates

At the lowest data rates, the 11.76% overhead may not allow all baud rates. Available rates
are as follows:
Data rate
64 to 127.999 kbps
128 to 191.999 kbps
192 to 255.999 kbps
256 to 383.999 kbps
384 to 511.999 kbps
512 kbps and above

12.4 Configuration

Chapter 5. FRONT PANEL OPERATION
Use the SELECT: Configure  Mode menu to select ESC++. Then, use the SELECT: Configure 
Misc  HiRateESC menu select the baud rate and asynchronous character format.

12.5 Effect on Eb/No Performance

Because the increase in transmitted data rate will cause a decrease in the Eb/No performance –
particularly at lower data rates where the percentage overhead is large – all of the published
data concerning BER versus Eb/No needs to be modified according to the table that follows:
Data rate
64 kbps to < 768 kbps
768 kbps to 1.5 Mbps
> 1.5 Mbps to 2.5 Mbps
> 2.5 Mbps to 7 Mbps
> 7 Mbps
The degradation is simply 10 x log (Overhead ratio).
The Eb/No displayed by the modem (SELECT: Monitor RX-Params) takes this into account in
the value that is calculated.
Baud rates available
1200, 2400, 4800
1200 to 9600
1200 to 14400
1200 to 19200
1200 to 28800
1200 to 38400
Overhead ratio (percentage)
19/17 (11.76%)
12/11 (9.09%)
29/27 (7.4%)
19/18 (5.56%)
64/63 (1.58%)
12–2
Revision 13
MN-CDM625
Eb/No degradation
0.48 dB
0.38 dB
0.31 dB
0.23 dB
0.07 dB