Wavecom W-SPECTRA (Automatic Monitoring System) V1.1.0 - Manual (Page 181)

WAVECOM Monitoring System W-SPECTRA, W-SPEED Manual V1.1.0 Transmission Modes
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With the help of the FFT-Analysis-Tool look for a SAT-MINI-M-HSD signal (bandwidth 40 kHz, QAM16 33.6
kSymbol/sec) with a lot of traffic.
In the Satellite mode menu choose Inmarsat, SAT-MINI-M-C-HSD.
The Session Window displays the start and end of a session. The “MES_ID” displayed is the return MESId
of the MES (Mobile Earth Station); the “Frequency” is a dummy value.
The Session List Window displays the results of the successfully decoded sessions. The decoded data is
saved as “Hsd.txt”.
Additional information:
See “ SAT Settings… ” on page 45.
See “ SAT System ” on page 219.
SI-ARQ
SI-ARQ is a simplex system similar to for example SITOR. SI-ARQ therefore also sounds similar to the
well-known SITOR system. Because data and pause blocks are longer in duration, the perception of a low-
er baud rate is created.
Parameter Value
Frequency range HF
Operation modes Simplex ARQ
Modulation FSK
Symbol rate 96.0, 192.0 and 200.0 Bd
Receiver settings DATA, CW, LSB or USB
Input format(s) AF, IF
Additional Info ITA-3
SI-ARQ operates at symbol rates of 96, 192 or 200 Bd on the radio link.
SI-ARQ uses the ITA-3 alphabet for data transmission and error detection. Data blocks usually consist of 5
or 6 characters.
One transmission cycle is made up of twice the length of a character block. If the information sending sta-
tion (ISS) receives an acknowledgement character, the next data block is sent with inverted phase or po-
larity. However, if the receiving station (IRS) requests a retransmission, the repeated block is sent with
unchanged polarity.
If the ISS does not receive the acknowledgement packet, it transmits a RQ block as is the case with SI-
TOR.
The software automatically detects SI-ARQ block lengths of four, five or six characters and displays this
information after phasing has been achieved. The polarity of the signal is automatically detected.
Transmission Sequence of SI-ARQ at 96 Baud with Five Characters
SI-AUTO
Fully automatic tuning to signal center, shift and transmission modes SI-ARQ (Mode A) and SI-FEC (Mode
B) may be achieved by selecting SI-AUTO mode.