Wavecom W61PC V7.5.0 - Manual (Page 166)

156  Transmission Modes WAVECOM Decoder W61PC/LAN Manual V7.5
Parameter Value
Modulation FM, SUB FSK
Symbol rate 1200 Bd
Center frequency 1700 Hz
Shift/Bandwidth 800 Hz
Receiver settings FM, BW = 12 kHz
Input format(s) AF, IF
Additional Info ITA-5
DSC is used on HF and VHF. On VHF the symbol rate is 1200 baud and the center frequency is 1700 Hz
and the shift is 800 Hz.
Selecting Options/Display offers the option of an ASCII or RAW bits display.
The complex structures of the DSC are described in detail in the ITU-Rec. M.493-11.
GOLAY/GSC
The GOLAY/GSC pager system originates in the USA and is based on the binary code found by Marcel GO-
LAY/GSC. GOLAY has been in use since 1973. The first standard defined only tone calling and could handle
a maximum of 400,000 addresses. After 1982 the system also allows for alphanumeric transmission and
up to 4 million addresses may be selected via a coded preamble.
Parameter Value
Frequency range VHF
Operation modes Broadcast FEC
Modulation FSK
Symbol rate 300/600 Bd adaptive
Receiver settings FM, BW = 15 kHz
Input format(s) IF
GOLAY Addressing Format
This illustration shows the basic address format of the Golay Sequential Code (GSC). It is constructed
from two code words which are derived using the Golay (23,12) algorithm. The bit rate for each code word
is 300 bit/s. Each received Golay word can contain up to three errors before integrity is compromised. The
GSC is asynchronously decoded. To separate adjacent addresses, a separator word (comma) is transmit-
ted at a rate of 600 bit/s.
The message format is based on eight BCH (15,7) code words that are grouped together to have exactly
the same length as an address. Messages and addresses are thus easily interleaved. Each message block
may contain up to 12 numeric or 8 alphanumeric characters. Messages which are longer than a single
block may be transmitted using any desired sequence of blocks. By implementing block coding, two errors
may be corrected in the BCH (15,7) codeword. The bits within a block are interleaved during transmission
which allows the correction of burst errors affecting up to 16 bits, which is equivalent to a fading protec-
tion of 27 ms.
GOLAY Data Block with Eight Alphanumeric Characters