WAVECOM Decoder W74PC, W-PCI/e, W-CODE, W-CLOUD Manual V9.1.0
Transmission Modes
247
Baud
Rate
User da-
ta
rate
(bps)
User data
rate (bps)
FEC coding
rate
Interleaver
No. of unknown
8-phase
sym-
bols (User Data)
No. of known 8-
phase symbols
(Channel Probe)
2400
2400
3 (8-PSK)
2 / 3
SHORT or LONG
32
16
2400
1200
2 (QPSK)
1 / 2
SHORT or LONG
32
16
2400
600
1 (BPSK)
1 / 2
SHORT or LONG
32
16
2400
300
1 (BPSK)
1 / 4
SHORT or LONG
32
16
2400
150
1 (BPSK)
1 / 8
SHORT or LONG
32
16
2400
75
1 (BPSK)
1 / 16
SHORT or LONG
32
16
2400
3600
3 (8-PSK)
No coding
ZERO
32
16
2400
2400
2 (QPSK)
No coding
ZERO
32
16
2400
1200
1 (BPSK)
No coding
ZERO
32
16
The user data is transmitted using a continuous frame structure. Each frame begins with a 33.33 ms pre-
amble containing 80 symbols, the next 176 symbols are divided into four 32-symbol data segments and
three 16-symbol channel probe segments.
At the end of transmission, a certain bit-pattern (in hexadecimal notation, 4B65A5B2, MSB first) is sent to
mark the end of message (EOM). The EOM sequence is followed by flush bits, which are for FEC coder
flushing and for the complete transmission of the remainder of the interleaver data block.
In most cases FEC and interleaver are used to combat the effects of fading, frequency shift, multipath ef-
fects and burst noise. User data is in this case first FEC encoded, interleaved, then mapped into PSK sym-
bol and transmitted in 32 symbol data segment. The 16 symbol channel segment transmitted between
every data segment has a known PSK pattern. Its purpose is to keep the demodulator, mainly the equaliz-
er, on track in spite of adverse propagation conditions during the HF transmission.
After the 176 symbol data-probe segment another frame beginning with the same 80-symbol preamble
follows immediately. This frame structure makes the synchronization of the demodulator in the mid of the
transmission very easy.
The STANAG-4285 decoder processes all the above configurations. This should be set manually in the
Frame Format
menu.
Generally STANAG-4285 transmits the user data in binary mode, i.e., it does not care what type of binary
data is transmitted. This should be defined by the higher layer using the STANAG 4285 mode. For this
reason the decoder displays the user data in
BINARY
,
HEX
,
ASCII ASYNC
,
ASCII ASYNC
(7 Data bits
and No Stop bit) or
ASCII SYNC
format selected from
Options | Message Type...
. The decoder stops
displaying data after the EOM bit pattern is received.
In the HEX display mode, the decoded binary data is just display as it is, MSB first.
In ASCII ASYNC mode, the bit stream is searched with ASCII ASYNC structure, i.e., one start-bit (0), 8
data-bits and at least one stop-bit (1). The 8 data-bits are LSB first. In addition to the EOM pattern, the
display will stop if more than 300 NULL characters are received or if the asynchronous data structure is vi-
olated more than 80 times.
16
16
16
32
32
32
32
80
symbols
80
symbols
Block 1
Block 2
Block 3
Block 4
T = 106.66 ms
33.33 ms
80
symbols
16
32
Preamble
Data symbols
Channel probe symbols
