User guide

MS-DMT Guide v1.04
Released 05-30-2014
130
APPENDIX G: DATA RATE AND INTERLEAVER SELECTION
S4415 which only supports one data rate makes life simpler for the user and provides very
robust operation under all channel conditions, but it is slow and thus not the best choice if the
channel supports faster data rates. S4285 and S4529 which are not autobaud compliant require
that both the TX and RX stations to be configured the to the same data rate and interlever
settings in advance and thus do not support Adaptive ARQ not being autobaud. However due to
their near constant re-sync known data transmitted during the payload, it makes them the
better suited modes for FEC Broadcast applications.
However for FEC only use, the user must select the data rate and interleaver for FEC operation
based on channel conditions manually. The use of serial tone modem waveforms in FEC modes
by stations in attended operation, unlike in unattended guard channel operations permits a
voice exchange to determine receive conditions on both ends, this holds true for Regional
Broadcast use as well, as the NCS or directed sending station can poll the net for signal report. In
two-way use of 110A serial tone FEC modes both stations can send at the same or different data
rate and Interleaver settings, where it is best to just make use of the LONG interleaver setting to
deal with any channel issues and minimum performance characteristics of the waveform data
rates. For guard channel operations the broadcast station can only to take into account TOD
propagation characteristics for the wavelength being used, seasonal effects and minimum
performance characteristics of the waveform data rates, thus 75-300bps should be used for
CONUS wide or OCONUS broadcasts and 75-600bps for regional broadcasts.
The use of serial tone modem waveforms in FEC modes by stations in attended operation, unlike
in unattended guard channel operations permits a voice exchange to determine receive
conditions on both ends, this holds true for Regional Broadcast use as well, as the NCS or
directed sending station can poll the net for signal report. In two-way use of 110A serial tone
FEC modes both stations can send at the same or different data rate and Interleaver settings,
where it is best to just make use of the LONG interleave setting to deal with any channel issues
and minimum performance characteristics of the waveform data rates. For guard channel
operations the broadcast station can only to take into account TOD propagation characteristics
for the wavelength being used, seasonal effects and minimum performance characteristics of
the waveform data rates, thus 75-300bps should be used for CONUS wide or OCONUS
broadcasts and 75-600bps for regional broadcasts.
Most MARS-to-MARS peer-to-peer and regional broadcast communications takes place within 2-
12Mhz NVIS where the 3-7Mhz range sees the most use and where the 3 and 4Mhz range sees
the bulk of the use and which has the highest noise levels and fading conditions next to 2Mhz.
As such the recommended Interleaver setting is always LONG. Data rates beyond 600bps will