[Sls-slp] Security, NGU and New TC services and there effect on COP-1

Greenberg, Edward (313B) edward.greenberg at jpl.nasa.gov
Tue Oct 13 16:35:43 UTC 2009

Last week Majorie De Lande Long posed the question as to how the new
security header and its placement in the TC frame would effect COP-1.
A few weeks ago Greg and I had a long discussion with Matt Cosby on this
very topic.  We concluded that if the security was processed prior to the
COP there is no issue.  The only problem is that the FEC decoding should be
performed before the security process.

This leads us to another item that can be put on the table.  The CCSDS is in
the final phases of approving the LDPC codes and the new generation uplink
team is investigating how to improve performance for commanding.  One of the
things being considered is to use the LDPC code for all uplinks by placing
it in the physical layer.  I this way the code would be put on synchronously
to carry the synchronous bits required in the link but independent of the
frames contain in the link.  Thus taking advantage of the 8 db gain provided
by the coding without changing the link layer protocol.  One of the benefits
of this approach is that the TC link layer protocol need not be modified and
ESA's current flight command decoder implementation need not be changed. The
only that that would be required on the flight side is an LDPC decoder with
a security processor that outputs the TC frame as currently defined
(eliminating the inserted security data fields and decrypting the data frame
data field.  


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