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<p class=MsoNormal style='margin-bottom:10.0pt'><span style='font-size:11.0pt;
font-family:"Calibri","sans-serif";color:#1F497D'>Dear </span><span
style='font-family:"Calibri","sans-serif"'>Unnikrishnan E</span><o:p></o:p></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>We are working on your questions and we will have a reply back
to you by next week. Thank you for your inquiry.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Best regards,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Greg Kazz<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Chairman CCSDS SLS-SLP WG<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'>
<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> Unnikrishnan E
[mailto:unnikrishnane@yahoo.com] <br>
<b>Sent:</b> Thursday, September 17, 2009 11:10 PM<br>
<b>To:</b> Kazz, Greg J (313B)<br>
<b>Cc:</b> slp@mailman.ccsds.org<br>
<b>Subject:</b> proximity-1 clarifications<o:p></o:p></span></p>
</div>
<p class=MsoNormal><o:p> </o:p></p>
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<p class=MsoNormal style='margin-bottom:10.0pt'><span style='font-family:
"Calibri","sans-serif"'>Dear Sir,</span><o:p></o:p></p>
<p class=MsoNormal style='margin-bottom:10.0pt'><span style='font-family:
"Calibri","sans-serif"'>We are implementing CCSDS proximity-1 protocol by
referring to Recommended Standard CCSDSS 211.0-B-4 Blue Book July 2006 and
Green book for additional information. Request to clarify the following
points for our implementation. </span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:0in;margin-right:0in;margin-bottom:
10.0pt;margin-left:51.75pt;text-indent:-.25in'><span style='font-family:"Calibri","sans-serif"'>1.</span><span
style='font-size:7.0pt'> </span><span
style='font-family:"Calibri","sans-serif"'>SCID (Spacecraft ID)</span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:0in;margin-right:0in;margin-bottom:
10.0pt;margin-left:.5in'><span style='font-family:"Calibri","sans-serif"'>Do
the Proximity link and TC link on an Orbiter share the same SCID (space craft
id) or two separate SCIDs will be allotted. </span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:0in;margin-right:0in;margin-bottom:
10.0pt;margin-left:51.75pt;text-indent:-.25in'><span style='font-family:"Calibri","sans-serif"'>2.</span><span
style='font-size:7.0pt'> </span><span
style='font-family:"Calibri","sans-serif"'>ASM ( Attached Synchronization
Marker)</span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:0in;margin-right:0in;margin-bottom:
10.0pt;margin-left:.5in'><span style='font-family:"Calibri","sans-serif"'>When
convolutional coding is not selected any error is allowed in the ASM (24
bits) for synchronization.</span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:0in;margin-right:0in;margin-bottom:
10.0pt;margin-left:.5in'><span style='font-family:"Calibri","sans-serif"'>When
convolutional coding is selected is ASM also convolutionally encoded. </span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:0in;margin-right:0in;margin-bottom:
10.0pt;margin-left:51.75pt;text-indent:-.25in'><span style='font-family:"Calibri","sans-serif"'>3.</span><span
style='font-size:7.0pt'> </span><span
style='font-family:"Calibri","sans-serif"'>Data Ambiguity Resolution </span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:0in;margin-right:0in;margin-bottom:
10.0pt;margin-left:.5in'><span style='font-family:"Calibri","sans-serif"'>What
is the suggested method for data ambiguity resolution if it is not performed
by the Physical layer.</span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:0in;margin-right:0in;margin-bottom:
10.0pt;margin-left:.5in'><span style='font-family:"Calibri","sans-serif"'> Is
phase ambiguity always resolved at the physical layer by eg., with
differential modulation technique. </span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:0in;margin-right:0in;margin-bottom:
10.0pt;margin-left:51.75pt;text-indent:-.25in'><span style='font-family:"Calibri","sans-serif"'>4.</span><span
style='font-size:7.0pt'> </span><span
style='font-family:"Calibri","sans-serif"'>Removal of IDLEs at receiving side
</span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:0in;margin-right:0in;margin-bottom:
10.0pt;margin-left:.5in'><span style='font-family:"Calibri","sans-serif"'>Is
searching for the first occurrence of ASM in the received bits sufficient to
remove the IDLEs.</span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:0in;margin-right:0in;margin-bottom:
10.0pt;margin-left:51.75pt;text-indent:-.25in'><span style='font-family:"Calibri","sans-serif"'>5.</span><span
style='font-size:7.0pt'> </span><span
style='font-family:"Calibri","sans-serif"'>Synchronization Procedure </span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:0in;margin-right:0in;margin-bottom:
10.0pt;margin-left:.5in'><span style='font-family:"Calibri","sans-serif"'>Is
searching for the first occurrence of ASM in the received bits sufficient for
synchronization. How any ‘bit slips’ or patterns of ASM in the data bits are
taken care in the protocol.</span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:0in;margin-right:0in;margin-bottom:
10.0pt;margin-left:51.75pt;text-indent:-.25in'><span style='font-family:"Calibri","sans-serif"'>6.</span><span
style='font-size:7.0pt'> </span><span
style='font-family:"Calibri","sans-serif"'>Variable and Fixed frame length.</span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:0in;margin-right:0in;margin-bottom:
10.0pt;margin-left:.5in'><span style='font-family:"Calibri","sans-serif"'>Is
there any difference in the synchronization procedure for variable length
frame and fixed length frame. I came across a suggestion to use fixed frame
length when BER is poorer than 10x-6. Please comment.</span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:0in;margin-right:0in;margin-bottom:
10.0pt;margin-left:51.75pt;text-indent:-.25in'><span style='font-family:"Calibri","sans-serif"'>7.</span><span
style='font-size:7.0pt'> </span><span
style='font-family:"Calibri","sans-serif"'>Availability of Reference
Implementations </span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:0in;margin-right:0in;margin-bottom:
10.0pt;margin-left:.5in'><span style='font-family:"Calibri","sans-serif"'>Is
any standard reference implementation (hardware or software) available for
carrying out protocol testing. </span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:0in;margin-right:0in;margin-bottom:
10.0pt;margin-left:.5in'><span style='font-family:"Calibri","sans-serif"'>Thanking
you,</span><o:p></o:p></p>
<p class=MsoNormal style='margin-bottom:10.0pt'><span style='font-family:
"Calibri","sans-serif"'>Unnikrishnan E</span><o:p></o:p></p>
<p class=MsoNormal style='margin-bottom:10.0pt'><span style='font-family:
"Calibri","sans-serif"'>Head, Digital Commn. Section,</span><o:p></o:p></p>
<p class=MsoNormal style='margin-bottom:10.0pt'><span style='font-family:
"Calibri","sans-serif"'>Digital System Group, </span><o:p></o:p></p>
<p class=MsoNormal style='margin-bottom:10.0pt'><span style='font-family:
"Calibri","sans-serif"'>ISAC, Bangalore, </span><o:p></o:p></p>
<p class=MsoNormal style='margin-bottom:10.0pt'><span style='font-family:
"Calibri","sans-serif"'>India </span><o:p></o:p></p>
</td>
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<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri","sans-serif"'><o:p> </o:p></span></p>
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