CDM-625 Advanced Satellite Modem
Revision 1
ESC++
MN-0000036 (Ref MN/CDM625.IOM)
12–2
12.3 Available Baud Rates
At the lowest data rates, the 11.76% overhead may not allow all baud rates. The following table
shows available rates:
Data rate
Baud rates available
64 to 127.999 kbps
1200, 2400, 4800
128 to 191.999 kbps
1200 to 9600
192 to 255.999 kbps
1200 to 14400
256 to 383.999 kbps
1200 to 19200
384 to 511.999 kbps
1200 to 28800
512 kbps and above
1200 to 38400
12.4 Configuration
To use this mode, the user should select
ESC++
from the
SELECT: Configure
Æ
Mode
menu.
The baud rate and async character format are then selected from the
SELECT: Configure
Æ
Misc
Æ
HiRateESC
menu. This is described in
Chapter 5. FRONT PANEL OPERATION
.
12.5 Effect on Eb/No performance
Because – particularly at lower data rates where the percentage overhead is large – the increase in
transmitted data rate will cause a decrease in the Eb/No performance, all of the published data
concerning BER versus Eb/No needs to be modified according to the table below:
Data rate
Overhead ratio (percentage) Eb/No degradation
64 kbps to < 768 kbps
19/17 (11.76%)
0.48 dB
768 kbps to 1.5 Mbps
12/11 (9.09%)
0.38 dB
> 1.5 Mbps to 2.5 Mbps
29/27 (7.4%)
0.31 dB
> 2.5 Mbps to 7 Mbps
19/18 (5.56%)
0.23 dB
> 7 Mbps
64/63 (1.58%)
0.07 dB
The degradation is simply 10 * log (Overhead ratio)
The Eb/No displayed by the modem
(SELECT: Monitor
Æ
RX-Params)
takes this into account
in the value that is calculated.
