Wavecom W61PC V7.5.0 - Manual (Page 168)

158  Transmission Modes WAVECOM Decoder W61PC/LAN Manual V7.5
On the receiving side up to 3 incorrect bits may be corrected using a (24, 12) Golay code. In addition the
data bits are interleaved (bit interleaving).
The complex G-TOR system is described in detail by the manufacturer KANTRONICS in a booklet ("G-TOR,
The New Mode, Articles, Charts, Protocol", edited by Shelley Marcotte).
Two code tables are defined for this mode, Code Table 0 and Code Table 1, which may be selected from
Options/Code Table.
GW-FSK
GW-FSK is used by Globe Wireless on the Maritime Data Network of the company.
Parameter Value
Frequency range HF
Operation modes Simplex ARQ
Modulation FSK
Symbol rate 100 or 200 Bd
Shift 200 Hz
Receiver settings DATA, CW, LSB or USB
Input format(s) AF, IF
Additional Info ASCII
The GW-FSK frame consists of three sections: header, data and control. At 100 baud the size of the data
field is 48 bits and at 200 baud the size is increased to 112 bits. Each frame contains 6/14 characters or
data bytes. For smaller packets a filler ‘<’ is used. For 100 baud the error detection is unknown while the
200 baud sub mode uses a 16 bit CRC for error detection.
GW-FSK operates adaptively so the baud rate can be either 100 or 200 baud. The baud rate depends on
propagation as well as the type of transmission. Station idle and start of communication is done with 100
baud. Traffic and GPS position messages are transmitted at 200 baud.
Station idle and ID signals are transmitted at short intervals whenever the shore station is idle. The format
is synchronous ASCII.
Most of the traffic is compressed. From time to time uncompressed GPS position data in NMEA format is
transmitted on ship frequencies.
GW-FSK is found on all short wave maritime bands. More information is available on
http://www.globewireless.com .
GW-OFDM
GW-OFDM is a HF data-transmission system wholly owned and operated by GlobeWireless. Twenty-four
HF coastal radio stations provide connection to the land network. Additionally, GlobeWireless offers an
email service for vessels around the world. The equipment required by the user consists of a proprietary
GlobeWireless data modem (e.g. GL 5100) and shortwave radio equipment, and is installed and main-
tained by the company.
Parameter Value
Frequency Range HF
Operation modes ARQ
Modulation OFDM with DQPSK
Center Frequency 1500Hz
Shift/Bandwidth 750–2000 Hz