970630: NOAAPORT Changes-NOUS (fwd)

• To: nws-changes@xxxxxxxxxxxxxxxx
• Subject: 970630: NOAAPORT Changes-NOUS (fwd)
• From: Linda Miller <lmiller@xxxxxxxxxxxxxxxx>
• Date: Mon, 30 Jun 1997 07:00:50 -0600 (MDT)

705
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
END
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