Wavecom W40PC, Руководство пользователя

Страница: 190 / 264

182
•
Transmission Modes WAVECOM Decoders v6.15 W40PC, W41PC, W51PC
To ensure, that the system can handle drifting signals or a coarsely adjusted center frequency,
”
AFC ” may be enabled in the " Demodulator " menu. The carrier tracking function is now
activated If the deviation between the tracked and the adjusted center frequency is too large,
the center frequency should be corrected. The carrier tracking only works over a range of:
•
DBPSK Center ± 8 Hz
Hence adjustment of the center frequency must be accurate.
In contrast to PSK-31, no DQPSK modulation exists.
RUM-FEC
Parameter Value
Frequency range HF
System FEC
Baudrate(s) 164.5 and 218.3, variable 30-650 Baud
Modulation SSB or DIRECT-FSK
Receiver settings CW, LSB or USB
Signal source(s) AF, HF or IF
Alphabet 16 Bit redundancy
RUM-FEC operates at speeds of 164.5 and 218.3 Baud on the radio link.
The HNG-FEC and RUM-FEC modes are technically very similar. RUM-FEC alphabet has a
codeword length of 16 bits where each of the 32 used bit combinations corresponds to an ITA-
2 character.
The RUM-FEC alphabet is designed to obtain a maximum Hamming distance for error
detection and has deep interleaving. The actual ITA-2 alphabet is not contained in the code
table. As in HNG-FEC error correction is performed by table look-up of the bit pattern
(character) closest resembling the character in error.
RUM-FEC has a bit interleaving of 128 bits, each new character starting at intervals of 16 bits.
The software synchronizes to traffic as well as idle bit patterns.
Error correction may be enabled or disabled using the “
ECC
” item in the “Options” menu.