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GSS6100 and SimCHAN user manual
© Spirent Communications Plc 2005 - 2007
H-1
SBAS Correction Data Files
Appendix H: SBAS Correction Data Files
H.1 Creating and editing a SBAS correction data file
In SBAS mode, the GSS6100 produces a SBAS correction data message
from the user supplied *.WAS file (an ASCII format file). The default
correction data file is WAAS_DEF.WAS. The file appropriate to WAAS
change note 3 is SBAS_CN3.WAS
Raw SBAS correction data has the basic format shown in Figure 7-13.
Figure 7-13 Raw SBAS correction data diagram
250 BITS
6 BIT MESSAGE TYPE IDENTIFIER (0-63)
24-BITS
212 BIT
DATA
3 CONTINGUOUS BLOCKS
8 BIT PREAMBLE OF 24 BITS TOTAL IN
PARITY
As can be seen from the diagram above the message can be split into two
main segments, data and parity.
Each line of data in the *.WAS file corresponds to 1 second of data
(assuming a data rate of 500 symbols/sec). The 226 data bits are encoded
into 57 hex characters, see Figure 7-14.
Figure 7-14 SBAS message structure