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NOUS40 KWBC 301121
FOS/NOAAPORT NOTICE NO. 1092 JUNE 30... 1997
ATTN FOS/NOAAPORT USERS
SUBJECT ERROR CONTROL CHANGES PLANNED FOR NOAAPORT
SATELLITE BROADCAST
OUR EARLY EXPERIENCE WITH THE NOAAPORT SATELLITE BROADCAST
NETWORK /SBN/ HAS SHOWN THE NEED FOR IMPROVEMENTS IN THE
TECHNIQUE USED FOR ERROR CONTROL. ACCORDINGLY AN ALTERNATIVE
DATA CODING SCHEME PROVIDING FORWARD ERROR CORRECTION HAS BEEN
DEVISED AND IS CURRENTLY UNDER TEST. UPON SUCCESSFUL COMPLETION
OF THE TESTS AND ACCEPTANCE OF THE RESULTS BY THE NATIONAL
WEATHER SERVICE A DESIGN CHANGE WILL BE MADE IN THE SBN
AFFECTING
THE MASTER GROUND STATION /MGS/ AND ALL OF THE AWIPS SITE GROUND
STATIONS /SGS/. NOAAPORT RECEIVE SYSTEM /NRS/ USERS WILL ALSO BE
AFFECTED IN THAT THE REPLACEMENT DATA CODING SCHEME WILL BE
INCOMPATIBLE WITH THAT NOW IN USE.
THE REPLACEMENT SCHEME IS A ROBUST CONCATENATED TYPE WHICH
COMBINES THE FEATURES OF A CONVOLUTIONAL ENCODER A DATA
INTERLEAVER AND A REED-SOLOMON ERROR CORRECTION CODE. A NEW SBN
DEMODULATOR MODEL SDR54A PRODUCED BY EFDATA CORPORATION WILL
INCORPORATE THE FORWARD ERROR CORRECTION SCHEME AND THESE
DEMODULATORS WILL BE INSTALLED IN THE NWS SGS SITES THROUGH A
PHASED CUT-OVER PLAN.
THE NOAAPORT RECEIVE SYSTEM DOCUMENTATION WILL BE UPDATED TO
REFLECT THE CHANGES IN THE CODING SCHEME TO ENABLE CONSTRUCTION
AS AN ALTERNATIVE TO PURCHASE OF A MANUFACTURED DEMODULATOR.
MORE INFORMATION ON THIS IS EXPECTED TO BE FORTHCOMING IN THE
NEAR FUTURE AND WILL BE DISTRIBUTED TO THOSE ON THE NOAAPORT
MAILING LIST.
THE PERTINENT CHARACTERISTICS OF THE NEW DATA STREAM CODE ARE
AS FOLLOWS
NWSTG CHANNEL DATA RATE 1536 KBPS
GOES EAST CHANNEL DATA RATE 1536 KBPS
GOES WEST CHANNEL DATA RATE 1536 KBPS
MODULATION QPSK
SCRAMBLER ON
CONVOLUTIONAL CODE CONSTRAINT LENGTH K 7
CONVOLUTIONAL CODE RATE 3/4
INTERLEAVE DEPTH 16
REED-SOLOMON CODE /N K T/ /225 205 10/ PER
IESS - 308
APPENDIX G
REED-SOLOMON SYMBOL SIZE 8 BITS
IF THE REPLACEMENT SYSTEM IS ACCEPTED IT IS PLANNED TO PHASE
IN THE INSTALLATION THROUGH A TRANSITION PLAN NOW PROJECTED TO
BEGIN IN EARLY SEPTEMBER AND COMPLETE BY MID-SEPTEMBER. THE
PLAN
REQUIRES THAT THE SATELLITE BROADCAST FREQUENCIES FOR ALL
CHANNELS BE SHIFTED SEQUENTIALLY. AFTER COMPLETION OF THE
TRANSITION THE NEW FREQUENCIES WILL BE
DOWNLINK DOWNLINK BANDWIDTH
CARRIER /MHZ/ IF /MHZ/ /KHZ/
------------- -------- ---------
NWSTG 3990.225 1159.755 1550
GOES EAST 3994.1 1155.9 1550
GOES WEST 3991.775 1158.225 1550
RICHARD K. THIGPEN
CHIEF NETWORK MONITORING ANALYSIS BRANCH
OFFICE OF SYSTEMS OPERATIONS
NATIONAL WEATHER SERVICE
301-713-0864X164
RICHARD.THIGPEN NOAA.GOV
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