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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>For your information.<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<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>
<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"'> Kazz, Greg J (313B)
<br>
<b>Sent:</b> Thursday, September 24, 2009 4:45 PM<br>
<b>To:</b> 'Unnikrishnan E'<br>
<b>Cc:</b> slp@mailman.ccsds.org<br>
<b>Subject:</b> RE: proximity-1 clarifications<o:p></o:p></span></p>
</div>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Dear Unnikrishnan E,<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'>My answers are below in between ** **.<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>
<table class=MsoNormalTable border=0 cellspacing=0 cellpadding=0>
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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. <o:p></o:p></span></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;
margin-left:.5in'><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>** The orbiter is only assigned one spacecraft ID for all space
links. There is the concept of a Global SCID (GSCID) as well. It consists of
the SCID plus the Transfer Frame Version Number. **</span><span
style='font-size:11.0pt;font-family:"Calibri","sans-serif"'> </span><o:p></o:p></p>
<p class=MsoNormal style='margin-bottom:10.0pt'><span style='font-size:11.0pt;
font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></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 style='color:#1F497D'> ** implementation
dependent as to how many bit errors are allowed in the ASM by the frame
synchronization process – typically very few bit errors in the ASM are
allowed **</span><o:p></o:p></span></p>
<p class=MsoNormal style='margin-bottom:10.0pt'><span style='font-size:11.0pt;
font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></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
style='color:#1F497D'> ** correct **</span><o:p></o:p></span></p>
<p class=MsoNormal style='margin-bottom:10.0pt'><span style='font-size:11.0pt;
font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></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. <o:p></o:p></span></p>
<p class=MsoNormal style='margin-bottom:10.0pt'><span style='font-size:11.0pt;
font-family:"Calibri","sans-serif";color:#1F497D'>** CCSDS documents say to
use ASM to resolve data ambiguity. ** <o:p></o:p></span></p>
<p class=MsoNormal style='margin-bottom:10.0pt'><span style='font-size:11.0pt;
font-family:"Calibri","sans-serif";color:#1F497D'>** I will forward your
question about phase ambiguity resolution on to my colleague, Dennis Lee for
an answer **<o:p></o:p></span></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.<o:p></o:p></span></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>**
I don’t understand what you mean by “remove IDLE data” in this context,
however IDLE data should be ignored until the first occurrence of the ASM is
detected. **</span><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>
</span><o:p></o:p></p>
<p class=MsoNormal style='margin-bottom:10.0pt'><span style='font-size:11.0pt;
font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></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.<o:p></o:p></span></p>
<p class=MsoNormal style='margin-bottom:10.0pt'><span style='font-size:11.0pt;
font-family:"Calibri","sans-serif";color:#1F497D'>** This ASM pattern was
chosen as to minimize the probability of that pattern occurring in the data
(low autocorrelation). **<o:p></o:p></span></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.<o:p></o:p></span></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;
margin-left:.5in'><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>**Here again we are talking about implementation issues. Fixed
length frame synchronization is easier to implement. However, We envisioned
Prox-1 to transfer messages across the Proximity Link. Messages are typically
of variable length and are most efficiently transported over an asynchronous
data link. However some agencies have implemented Prox-1 having the transmitter
generating fix length frames, but having the receiver handle both fixed and
variable length frames. From a performance point of view, the fixed
length frame synchronization typically would achieve synchronization much
faster than on a variable length frame. **</span><span style='font-size:11.0pt;
font-family:"Calibri","sans-serif"'> </span><o:p></o:p></p>
<p class=MsoNormal style='margin-bottom:10.0pt'><span style='font-size:11.0pt;
font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></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. <o:p></o:p></span></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;
margin-left:.5in'><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>** I will poll the CCSDS agencies to find out who has such an implementation
and if it is available. For example, NASA/JPL has some of the Proximity-1
functions in a reference implementation, but I am currently uncertain about
it’s availability. **</span><o:p></o:p></p>
<p class=MsoNormal style='margin-bottom:10.0pt'><span style='font-size:11.0pt;
font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></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>
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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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