[Sls-slp] RE: proximity-1 clarifications

Kazz, Greg J (313B) greg.j.kazz at jpl.nasa.gov
Fri Sep 18 18:38:28 UTC 2009

Dear Unnikrishnan E

We are working on your questions and we will have a reply back to you by next week. Thank you for your inquiry.

Best regards,

Greg Kazz

From: Unnikrishnan E [mailto:unnikrishnane at yahoo.com]
Sent: Thursday, September 17, 2009 11:10 PM
To: Kazz, Greg J (313B)
Cc: slp at mailman.ccsds.org
Subject: proximity-1 clarifications

Dear Sir,
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.
1.       SCID (Spacecraft ID)
Do the Proximity link and TC link on an Orbiter share the same SCID (space craft id) or two separate SCIDs will be allotted.
2.       ASM ( Attached Synchronization Marker)
When convolutional coding is not selected any error is allowed in the ASM (24 bits) for synchronization.
When convolutional coding is selected is ASM also convolutionally encoded.
3.       Data Ambiguity Resolution
What is the suggested method for data ambiguity resolution if it is not performed by the Physical layer.
 Is phase ambiguity always resolved at the physical layer by eg., with differential modulation technique.
4.       Removal of IDLEs at receiving side
Is searching for the first occurrence of ASM in the received bits sufficient to remove the IDLEs.
5.       Synchronization Procedure
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.
6.       Variable and Fixed frame length.
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.
7.       Availability of Reference Implementations
Is any standard reference implementation (hardware or software) available for carrying out protocol testing.
Thanking you,
Unnikrishnan E
Head, Digital Commn. Section,
Digital System Group,
ISAC, Bangalore,

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