Wavecom W61PC V7.5.0 - Manual (Page 179)

WAVECOM Decoder W61PC/LAN Manual V7.5 Transmission Modes  169
MIL-188-110-39Tone, (MIL-188-110A/B Appendix C)
MIL-STD-188-110 39 Tone is a non-mandatory part of the MIL-STD-188-110 military standard for use by
all departments and agencies of the Department of Defense.
Parameter Value
Frequency range HF
Operation modes PSK, Simplex
Modulation 39 tone Q-DPSK
Symbol rate 44.44 Bd
Center frequency 1800 Hz
Receiver settings DATA, CW, LSB or USB
Input format(s) AF, IF
Definition
The modulation technique used in this mode consists of differential quadrature phase shift keying (QDPSK)
of 39 orthogonal sub carriers in the range from 675Hz to 2812.5 Hz, and an additional unmodulated Dop-
pler reference tone at 393.75Hz.
The modulation speed (symbol rate) is always 44.44 Bd. Through the transmission of redundant infor-
mation on certain tones, different user data rates can be achieved within a range of 75 to 2400 bps.
This mode uses FEC and interleaving to combat the effects of fading, frequency shift, multipath, and burst
noise.
The user data is transmitted using a continuous frame structure with a variable block length (number of
symbols), depending on user data rate and message type.
Each transmission starts with a preamble, consisting of three phases, followed by block synchronization
and data segments. The data block immediately follows the next block synchronization segment defining
again the start of the next data block. This repeated frame structure enables synchronization of the de-
modulator at any time of transmission.
The end of transmission is determined by an EOM sequence (at least ten ones "1").
Data Display
There are two different types of data transmissions - synchronous and asynchronous.
In the synchronous data mode, the data is bit synchronously displayed as 7 bit characters, while in the
asynchronous mode, different character lengths are possible using start, stop and parity bits. The parity,
start and stop bits, as well as the special "null" characters, inserted by the modem and not being part of
the data stream, are ignored by the display.
The decoder stops displaying data after the EOM sequence is received and goes to Sync state and resyn-
chronizes.
In Options/Frame Format the user data rate and interleaver length can be set.
In Options/Diversity a value between Time / Frequency and Frequency Only diversity can be select-
ed. The value must be set correctly for all user data rates except 2400 and 1200 bps.
In Options/Message Type all the different character lengths and number of extracted data bits can be
set.