Wavecom W61PC V7.5.0 - Manual (Page 169)

WAVECOM Decoder W61PC/LAN Manual V7.5 Transmission Modes  159
Parameter Value
Symbol rate 62.5 Bd per carrier (max. 32 carriers)
AFC Pilot tone tracking over the full PB bandwidth
Receiver Settings USB (automatic polarity recognition)
Input format(s) AF, IF
Additional Info Adaptive number of carriers, compression
GW-OFDM-Modulation and Protocol
GlobeWireless-OFDM employs a dynamic increase and decrease in the number of OFDM carriers; the num-
ber of carriers can vary between 12 and 32. Each carrier is modulated with DQPSK.
The main specifications of GW-OFDM are:
 12 to 32 subcarriers
 DQPSK modulation
 62.5 Hz subcarrier spacing (symbol duration 16ms)
 Guard interval duration 2ms
 700-2700 Hz occupied bandwidth
 Pilot tone for synchronization and frequency tracking
The system ensures error free data exchange with an ARQ protocol – if a reception error occurs, the in-
formation receiving station (IRS) can request the retransmission of the corrupted packet from the infor-
mation sending station (ISS). To reduce the peak-to-average power ratio, a scrambler is used. Different
compression algorithms are used to achieve efficient data throughput.
Decoder output
The decoder can recognize and decode the following packet types:
Packet type Function Source
IDLE Idle frame ISS
DATA Data frame ISS
RQ Frame with Acknowledge(ACK)
or Not Acknowledge(NAK) pack-
ets
IRS
OVER ISS requests to become IRS ISS
FORCED OVER IRS accepts the OVER IRS
END ISS indicates end of Transmission ISS
END ACK IRS acknowledges end of trans-
mission
IRS
MYCALL Contains selcall of the calling sta-
tion
Not specified
The decoded packet types are shown in the upper status bar.
In the decoded output, session information is printed in addition to decoded text: the start of a transmis-
sion [START OF TRANSMISSION], session end [END OF TRANSMISSION (END)], [END OF TRANSMISSION
(END ACK)], and loss of signal [NO SIGNAL CLOSE FILE] are indicated.
After a transmission has started and the data has been decoded successfully, transmission information is
printed as follows:
“Transmission ID: NNN, Date_Time: JJJMMDD_HHMMSS, Type: cma|cmb|cmc, Ship: CS-Ship, Coast: CS-
Coast”
Optionally, the text “CRC-Error” can be shown. When the decoder recognizes and decodes the compressed
packets, it indicates the type to the user.
After the transmission information field, the decoded email is shown.