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<p class=MsoNormal>All,<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Please let me know if you would be interested in having a
discussion on the use of data compression as a technique towards conserving
bandwidth on the uplink.<o:p></o:p></p>
<p class=MsoNormal>In other words, do you think compression is likely to be a
big payoff and manageable, and worthy of inclusion in a CCSDS NGU standard,
etc. ?<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>A current example of using compression on the uplink is the
NASA Mars Science Laboratory Project which is tentatively planning to use one
of the Lempel Ziv (LZ) encoders for compressing flight software loads. <o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Data compression could be another technique that the NGU WG
should consider for standardization for NGU applications. Considering that the
CCSDS Convolutional Code can approximately provide about a 5 db gain, and the LDPC
about 7 db. if we can get 3+ db from compression it might be a worthwhile
contender for consideration.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>So this additional work could manifest itself by involving agency
collaboration on studying the various compression candidates for use on the
uplink. If that is the case, then NGU would need support from the MHDC WG in
supporting such a study.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Some of the question we could consider asking ourselves are:<o:p></o:p></p>
<p class=MsoNormal> <o:p></o:p></p>
<p class=MsoNormal>(1) Can we come up with uplink data sets that are good
examples of the type of uplink data that requires compression and that compresses
well?<o:p></o:p></p>
<p class=MsoNormal>(2) How much improvement might we get from different
variations of compression algorithms on the data types that are worth studying ?<o:p></o:p></p>
<p class=MsoNormal>(3) Have we convinced ourselves that the NGU data volume
problem is significant enough in the first place to warrant compression ?<o:p></o:p></p>
<p class=MsoNormal>(4) Is 2:1 lossless compression our goal ?<o:p></o:p></p>
<p class=MsoNormal>(5) What are the candidate compression algorithms and what
are the metrics to judge them by ?<o:p></o:p></p>
<p class=MsoNormal>(6) I don't know how much interest there is from other CCSDS
member agencies on this topic <span style='font-family:"Times New Roman","serif"'>–</span>
please let me know.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>If I get positive feedback from member agencies on this
survey, then I will pass this along to the MHDC WG to see if we can start up an
email dialog with them before the London meeting and also schedule some time in
London if necessary to meet with them.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Best regards,<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Greg Kazz<o:p></o:p></p>
<p class=MsoNormal>Chairman CCSDS NGU WG <o:p></o:p></p>
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