Wavecom W74PC V8.7.0 - Manual (Page 240)

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Transmission Modes WAVECOM Decoder W74PC, W-PCI/e, W-CODE, W-CLOUD Manual V8.7.0
Parameter Value
Symbol rate 66000 Bd
Modulation OQPSK
Required SNR >15 dB (20 dB recommended)
Input format(s) IF
Unlike the other SAT modes, this mode does not automatically select a frequency. The user has to manu-
ally set the frequency and offset to the desired signal, which will then not be interfered with or changed by
the decoder (mode). The signal level should be at least 16 dB over the noise, a 20 dB level will deliver
good results.
Session start and end are automatically recognized, but if the signal is too weak, meaningful sessions will
not be decoded and consequently a session file will not be generated, even if some intermediate decoding
has occurred.
The following services are decoded:
 ISDN
Operation
With the help of the FFT-Analysis-Tool look for a SAT-B-C-HSD signal (bandwidth 100 kHz, OQPSK 66
kSymbol/sec) with a lot of traffic.
In the Satellite mode menu choose Inmarsat, SAT-B-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 43.
See “ SAT System ” on page 291.
SAT-C-TDM, SAT-C-TDMA, SAT-C-EGC
SAT-C is a satellite based store-and-forward low speed message transmission system operating in the L-
band to (forward direction) and from (return direction) the mobile earth stations (MES) and in the C-band
to and from the land earth stations (LES) and network control stations (NCS).
Parameter Value
Frequency range L-Band (TDM)
C-Band (TDMA)
Operation modes Broadcast/Duplex FEC/ARQ TDM/TDMA
Symbol rate 1200 Bd
Modulation BPSK
Required SNR >15 dB (20 dB recommended)
Receiver settings BW = 5-10 kHz
Input format(s) IF
Mobile stations may be maritime, land based or aeronautical. The channel rate in both directions is 1200
symbols/sec. Error protection is achieved by convolutional encoding with R = 1/2 and k = 7 giving a user
bit rate of 600 bps.
A block or frame of data in the forward direction (TDM) comprises 10368 symbols (8.64 s). Data is highly
interleaved to combat slow fades. It is also scrambled to ensure an even distribution of logical 1s and 0s