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<p class="MsoNormal"><span style="font-size:11.0pt">Ken,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> Did you have any comment about the use of Fibonacci vs Galois for maximal pattern randomizers? If so I think I missed it. As I remember Greg asked you to explain the difference in the seeds
for the two representations and said that both representations would be shown in his book.
<o:p></o:p></span></p>
<p class="MsoNormal" style="text-indent:.5in"><span style="font-size:11.0pt">My question is general CCSDS standards. I would like to see a standard, MatLab, IEEE, or whatever. For coding like BCH, that uses a polynomial that is not irreducible (only 4 terms
and it is “reducible”, g(x) = x^7+x^6 + x^2 + 1 can be factored into (x + 1)(x^6 + x + 1)), I do not know if a Fibonacci equivalent can generate the parity. Can it? If it can, then for the following reason, I suggest that for any future CCSDS book, we use
Fibonacci for all shift registers diagrams.<o:p></o:p></span></p>
<p class="MsoNormal" style="text-indent:.5in"><span style="font-size:11.0pt">A maximal pattern register diagram can be either in the Fibonacci or Galois type representation, as you have submitted for the long randomizer. I am recommending Fibonacci be used
in CCSDS books at least where maximal and Gold codes are covered, since the output pattern is easily seen based on the register contents. Since CCSDS does not recommend implementation, the user is free to use Galois for implementation if that is their preference.
It would be nice if we can help the understanding of engineers in the field that are not PhDs. The fact that you were asked to explain why the seeds for the Fibonacci and Galois are different is telling. <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> I do not agree with the comment made by Enrico? or was it GP?, that since the BCH or other code in the book used a Galois type format, that the maximal or Gold code representation used should
therefore be in Galois format. <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> I would love to hear your comments. (and can the BCH be shown in a Fibonacci format?)
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Thanks,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Victor <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:11.0pt">From:</span></b><span style="font-size:11.0pt"> Sank, Victor J. (GSFC-567.0)[SCIENCE SYSTEMS AND APPLICATIONS INC]
<br>
<b>Sent:</b> Monday, May 17, 2021 1:16 PM<br>
<b>To:</b> Andrews, Kenneth S (JPL-332B)[JPL Employee] <kenneth.s.andrews@jpl.nasa.gov><br>
<b>Cc:</b> Kazz, Greg J (US 312B) via SLS-SLP <sls-slp@mailman.ccsds.org>; Kazz, Greg J (US 312B) <greg.j.kazz@jpl.nasa.gov><br>
<b>Subject:</b> RE: Your LFSR OID frame RIDs affecting USLP, TM, AOS SDLPs<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Ken,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> Maximal pattern shift registers. LFSR<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> CCSDS is not supposed to make recommendations about implementation. For implementing I understand that the Galois shift register is sometimes preferred over the Fibonacci form. However, for
understanding and for setting an initial seed, Fibonacci has tremendous advantage because WYSIWYG, if you remember that phrase from the early Apple computers, what you see is what you get.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> You might also remember that we had a recent go-around in the code and synch WG about how to show these shift registers and we (GSFC) were recommending Fibonacci with particular labeling of the
cells so that the polynomial is directly related to the cells that are tapped. Yes, I realize that this can also be done for the Galois form. Another value of the Fibonacci with the particular cell numbering is that it is what MatLab uses. So when people
are doing simulations, no conversion is needed. <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> As you might remember there is an ambiguity between the associated polynomial and the shift register labeling. A particular pattern can be generated in one direction or the reverse. We had
a particular proposal and it turned out that MatLab used the same convention. Our proposal was discarded since it would be too much editing to get all the books to follow the same convention, and maybe other reasons. <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> But in any case, seems better from an understanding point of view to use Fibonacci.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Victor<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:11.0pt">From:</span></b><span style="font-size:11.0pt"> Kazz, Greg J (US 312B) <</span><a href="mailto:greg.j.kazz@jpl.nasa.gov"><span style="font-size:11.0pt">greg.j.kazz@jpl.nasa.gov</span></a><span style="font-size:11.0pt">>
<br>
<b>Sent:</b> Monday, May 17, 2021 12:31 PM<br>
<b>To:</b> Andrews, Kenneth S (JPL-332B)[JPL Employee] <</span><a href="mailto:kenneth.s.andrews@jpl.nasa.gov"><span style="font-size:11.0pt">kenneth.s.andrews@jpl.nasa.gov</span></a><span style="font-size:11.0pt">><br>
<b>Cc:</b> Sank, Victor J. (GSFC-567.0)[SCIENCE SYSTEMS AND APPLICATIONS INC] <</span><a href="mailto:victor.j.sank@nasa.gov"><span style="font-size:11.0pt">victor.j.sank@nasa.gov</span></a><span style="font-size:11.0pt">>; Kazz, Greg J (US 312B) via SLS-SLP
<</span><a href="mailto:sls-slp@mailman.ccsds.org"><span style="font-size:11.0pt">sls-slp@mailman.ccsds.org</span></a><span style="font-size:11.0pt">><br>
<b>Subject:</b> Your LFSR OID frame RIDs affecting USLP, TM, AOS SDLPs<o:p></o:p></span></p>
</div>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Hi Ken,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The SLP WG decided to put both of your diagrams into a new non-normative annex in USLP, TM, and AOS.<o:p></o:p></p>
<p class="MsoNormal">The text in the normative part of the link layer books will state:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="Paragraph5" style="mso-list:none">The TFDZ of an OID Transfer Frame shall be generated by use of a 32-cell Linear Feedback Shift Register (LFSR) with polynomial 1 + D + D<sup>2</sup> + D<sup>22</sup> +D<sup>32</sup><span style="font-family:"Courier New"">,
see Annex X.</span><o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Where Annex X is TBD and will be added by me to the document.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">We have some questions and requests for you:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<ol style="margin-top:0in" start="1" type="1">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo5"><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:black">Why does the initialization data differ from one figure to the other one?</span><span style="font-size:13.5pt;font-family:-webkit-standard;color:black"> </span><span style="font-size:11.0pt"><o:p></o:p></span></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo5">The ‘1’ in the figures are misleading to some WG members, please replace ‘1’ with D sub zero i.e., D<sup>0</sup> in the figures.<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo5">Consensus of WG was to specify the initialization vector
<o:p></o:p></li></ol>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks!<o:p></o:p></p>
<p class="MsoNormal">Greg<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Greg Kazz<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Principal Engineer<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Technical Group Supervisor,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">PSSE/EEISE/PPSE (312B)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Jet Propulsion Laboratory<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">4800 Oak Grove Dr., M/S 301-490<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="ES-MX" style="font-size:11.0pt">Pasadena, CA 91109</span><span style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="ES-MX" style="font-size:11.0pt">1+(818)393 6529(voice)</span><span style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">1</span><span lang="ES-MX" style="font-size:11.0pt">+(818)393 6871(fax)</span><span style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="ES-MX" style="font-size:11.0pt">email: </span><a href="mailto:greg.j.kazz@jpl.nasa.gov"><span lang="ES-MX" style="font-size:11.0pt">greg.j.kazz@jpl.nasa.gov</span></a><span style="font-size:11.0pt">
</span><span style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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