Wavecom W61PC V7.5.0 - Manual (Page 218)

208  Transmission Modes WAVECOM Decoder W61PC/LAN Manual V7.5
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 cor-
rection is performed by table look-up of the bit pattern (character) closest resembling the character in er-
ror.
RUM-FEC has a bit interleaving of 128 bits, each new character starting at intervals of 16 bits. The soft-
ware synchronizes to traffic as well as idle bit patterns.
Error correction may be enabled or disabled using the ECC item in the Options menu.
In RUM-FEC mode the signal polarity (sideband) can be manually selected by toggling the Polarity item in
the Demodulator menu. If polarity changes during a transmission, synchronization will not be lost.
SAT-AERO-P
The SAT-AERO system carries digital voice, fax and low speed data. The channels between aeronautical
Ground Earth Stations (GES) and Aircraft Earth Stations (AES) are A-BPSK or A-QPSK modulated with
600, 1200, 4800, 8400,10,500 and 21,500 bps.
Parameter Value
Frequency range L-band/C-band
Operation modes, symbol rate,
modulation
Inm-Aero (Forward Pd and Psmc logical channels)
Forward:
- P-channel packet switched data TDM: 600 bps, 1200 bps A-BPSK
(SDPSK), 10.5 kbps A-QPSK (OQPSK), convolutional FEC R = ½, k = 7
- C-channel circuit mode SCPC: 8.4 kbps A-QPSK (OQPSK), convolution-
al FEC R = 2/3, k = 7, 10.5 kbps A-QPSK (OQPSK), convolutional FEC
R = ½, k = 7
Return:
- R-channel slotted Aloha: 600 bps, 1200 bps A-BPSK (SDPSK), 4.8
kbps, 10.5 kbps A-QPSK (OQPSK), convolutional FEC R = ½, k = 7
- T-channel TDMA: 600 bps, 1200 bps A-BPSK (SDPSK), 10.5 kbps A-
QPSK (OQPSK), convolutional FEC R = ½, k = 7
- C-channel circuit mode SCPC: 8.4 kbps A-QPSK (OQPSK), convolution-
al FEC R = 2/3, k = 7, 10.5 kbps A-QPSK (OQPSK), convolutional FEC
R = ½, k = 7
Modulation A-BPSK (Aviation-BPSK), symmetrical, differential PSK (SDPSK)
A-QPSK (Aviation-QPSK), a variant of offset QPSK
Required SNR >15 dB (20 dB recommended)
Input IF
Four channel types are used: P(acket switched), R(andom), T(DMA) and C(ircuit switched). Currently only
the P channel can be decoded.
Two output formats may be selected, All Signaling Units or Messages Only. If All Signaling Units is
selected, all signaling units are shown in hexadecimal except empty signaling units, which are skipped. If
Messages Only is selected packet-mode user data is converted to readable text – control and manage-
ment packets are not decoded.
The satellite covering the Atlantic-East region transmits a 5,250 Bd A-QPSK P-channel on 1546.0705 MHz.
SAT-B
The SAT-B system carries digital voice, low and high speed data and telex. The forward direction channels
from land earth stations (LES or CES) to mobile earth stations (SES or MES) are 6 kBaud, 12 kBaud and
65.1 kBaud TDM or SCPC depending on service.
Parameter Value