WAVECOM Decoder W74PC, W-PCI/e, W-CODE, W-CLOUD Manual V9.1.0
Transmission Modes
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two CRC bytes. This input bit stream is then bit-interleaved and convolutional encoded. After that, the
symbol mapping for the different channels is done, and the resulting signals are applied to the DxPSK
modulators.
To extract the data from a PACTOR-III signal, the signal is demodulated with the appropriate number of
DxPSK-demodulators, according to the speed level. The center frequency must be adjusted to the center
between the lowest and highest tone in use. AFC (automatic frequency control) can be switched on or off.
After demodulation and bit synchronization, the symbols of the channels are combined to one bit stream,
which is de-interleaved and passed through a Viterbi-decoder. The CRC is used to check whether trans-
mission errors occurred. After successful synchronization, it may take several tens of seconds before any
text is output in the GUI.
In PACTOR-III, the data may be transmitted as ASCII without compression or can be compressed with
HUFFMAN or PSEUDO-MARKOV compression (PMC). In addition, run length encoding (RLE) is included.
PACTOR-4
PACTOR-4 is an adaptive transmission mode that provides higher throughput and improved robustness
compared to PACTOR-I, –II and -III. Ten so-called
Speed Levels (SL)
are specified, which are predefined
combinations of modulation type (DBPSK, DSSS-DBPSK, DSSS-DQPSK, BPSK, QPSK, PSK-8, QAM-16,
QAM-32) and channel coding (1/3, 1/2, 5/6).
Speed Level 1 uses two DBPSK-modulated carriers, similar to PACTOR-II and PACTOR-III, but the carriers
change frequencies within a frame. This is done in order to eliminate single-carrier distortions.
For levels 2 to 10, PACTOR-III uses a single PSK-modulated carrier at 1500 Hz with a bandwidth of about
2400 Hz and a modulation rate of 1800 baud. Levels 2 - 4 use spread-spectrum modulation in order to in-
crease the robustness. Levels 5 - 10 use BPSK to QAM-32, and an equalizer to eliminate the effects of the
transmission channel.
Parameter
Value
Frequency range
HF
Operation modes
Half-duplex synchronous ARQ
Modulation
2-Channel DBPSK (Level 1)
DSSS-DBPSK, DSSS-DQPSK (Level 2 - 4)
BPSK, QPSK, PSK-8, QAM-16, QAM-32 (Level 5 - 10)
Symbol rate
1800.0 Bd
Receiver settings
USB
Input format(s)
AF, IF
Additional Info
ITA-5 with block coding
HEX (Binary Output)
Initial link establishment is achieved using the frequency shift-keying (FSK) protocol of PACTOR-I, corre-
sponding to the lowest protocol level. If both calling and called stations are capable of PACTOR-4, auto-
matic switching to this protocol is done.
For decoding, the center frequency should be set to a value /- 50 Hz of the received signal. Polari-
ty (NOR or INV) has to be selected manually.
The decoder supports several output modes. Decoded Data shows the application-level data. Raw Frames
can be used to display the raw data, either with decompression or as received. In this mode, control sig-
nals are displayed as well.
If the "HEX" alphabet is selected, the data is displayed in binary (hex) and text, otherwise as normal text.
PCCIR
The entire call number is transmitted by consecutive tones in decade sequence. When two identical digits
are to be transmitted consecutively, then an eleventh frequency is used as a repetition identifier.
