Wavecom W61PC V7.5.0 - Manual (Page 287)

WAVECOM Decoder W61PC/LAN Manual V7.5 SAT System  277
your antenna at least 500 km!). By observing the Bulletin Board form the NCS the user may deduce which
spot beams are visible in his location.
Session Success (Fax)
Patience is required when monitoring satellite transmissions as the monitoring of sessions may fail, in par-
ticular fax sessions. The reasons for the failure may be:
 The W61PC monitoring system cannot synchronize to the traffic channel because the traffic chan-
nel is not in a spot beam seen by the antenna, or it is too weak. Check the FFT display
 The W61PC monitoring system cannot synchronize, or it may synchronize, but after some time it
loses synch, because the traffic channel is in a spot beam which is disturbed by a neighbor chan-
nel. This neighbor channel can be inactive at the beginning of the session, but is activated after a
while. Check the FFT display
 The session is terminated after less than 100 seconds and no fax is received. Many fax sessions
never start transmitting fax data, because the handshaking process at the beginning of the ses-
sion fails. The handshake may take as long as 120 seconds
 The fax transmission is successful, but the fax viewer does not display anything or displays only a
partial fax. This could be due to bit errors preventing the fax decoding process or because the fax
devices during the handshake agreed on a coding version not yet implemented in the WAVECOM
fax viewer
 The fax transmission is successful, but output is not the default .TIF file, but a .JBG file, because
fax encoding is according to recommendation T.82/85. Call WAVECOM for support on this issue
SAT-C-TDM, SAT-C-TDMA
The SAT-C system is a simple store-and-forward messaging system.
SAT-C has four operational channels:
NCS Common Channel (SAT-C-TDM)
 Continuous TDM
 8.64 s frame
 1200 symbols/s
 Scrambled, encoded, interleaved
 One bulletin board per frame
 Signaling, Enhanced Group Calls (EGC), polls (see below)
LES TDM (SAT-C-TDM)
 Continuous TDM or demand assigned by NCS
 8.64 s frame
 1200 symbols/s
 Scrambled, encoded, interleaved
 One bulletin board per frame
 Signaling and LES-mobile messages
MES Signaling Channel
 Slotted Aloha random access, 28 slots/frame, 120 bits/slot
 1200 symbols/s
 Scrambled, encoded
 Distress and normal calls, data reporting, NCS log-in, log-out (registration)
MES Message Channel (SAT-C-TDMA)
 TDMA
 1200 symbols/s
 Scrambled, encoded, interleaved