[Sls-slp] Proposed Update to Proximity-1 Hailing Sequence

[Greg Kazz]

Jean-Luc,

I believe we ensure backward compatibility of Proximity-1 on an 
enterprise  basis and for a specific time period. For example, for 
the Mars enterprise for a given period of time (MER/MEX era) all 
participating space agencies should agreed to operate the same 
version of the protocol. The same principle should be extended to the 
next generation of spacecraft at Mars (ExoMars, NASA Mars Scouts) 
whenever these spacecraft need to interoperate with one another.

Greg


At 11:38 PM 1/14/2008, Jean-Luc.Gerner at esa.int wrote:
>Greg,
>Given that many developments have been made with the current version of
>Prox-1, one should make sure of full backward compatibility. How can we
>ensure it?
>
>Cheers
>
>Jean-Luc Gerner
>TEC-ETN
>Tel: +31 71 565 4473
>
>
>
>              Greg Kazz
>              <greg.j.kazz at jpl.n
>              asa.gov>                                                     To
>              Sent by:                   sls-slp at mailman.ccsds.org
>              sls-slp-bounces at ma                                           cc
>              ilman.ccsds.org            Peter.M.Shames at jpl.nasa.gov,
>                                         tomg at aiaa.org,
>                                         Charles.A.Edwards at jpl.nasa.gov
>              15/01/2008 01:13                                        Subject
>                                         [Sls-slp] Proposed Update to
>                                         Proximity-1 Hailing Sequence
>
>
>
>
>
>
>
>
>
>
>All,
>
>Your comments on the following are welcome!
>
>Attached please find a word document containing a small enhancement
>to the current Proximity-1 Space Data Link Protocol Hailing Sequence
>in full and half-duplex. This modification was the result of the
>development of a reference implementation of the protocol at JPL by
>the Electra Transceiver Project. In their testing, members of the
>Electra team have identified the following modifications to the Space
>data link portion of the protocol. I believe these changes although
>slight, require a version change to that document, and cannot be
>considered Technical Corrigendum. Therefore, I propose a CCSDS BOF
>activity to be started now to solicit feedback on the proposed
>attached changes . My goal is to have sufficient time for all
>interested parties to review these proposed changes before the March
>meetings, so that we can move them out quickly for agency review thereafter.
>
>Summary of changes to Prox-1 hailing sequence:
>
> >1. Regarding the state transitions to S41 Radiate Carrier Only (Figure 6-1)
>full duplex in E9. Also E37 in half-duplex as well.
>
>
> >In a space environment, we can see that it is reasonable to include
> >the E9 event (Valid Transfer Frame received) while in State S34
> >(Send Hail Tail) as a transition to S41. The tail idle sequence was
> >especially provided in the case that Convolutional Encoding was
> >provided in order to ensure that a sufficient number of bits went
> >through the convolutional decoder for the decoding process to
> >terminate. However in that process, we now see that it's possible
> >for the caller to receive a valid frame in state S34 before going to
> >S35. The same logic also applies to half-duplex. See attachment for changes.
>
>2. Also, in the State Table for hailing, we are also recommending to
>CCSDS that the implementation note for transitioning from S35 to S41
>by achieving bit synchronization alone (i.e., valid frame not
>required) being an implementation specific transition be removed -
>since we cannot justify its existence anymore. The same
>implementation option will also be removed from the text for
>half-duplex as well. See attachment.
>
>
>Note that the Word revision feature does not allow for redlines of
>diagrams. Therefore in this text, I will note the changes to the two
>State Diagrams. All other changes are marked in RED and or strike out
>text where appropriate.
>
>Diagram changes:
>
>Figure 6 -1:  Full Duplex State Transition Diagram
>
>State S41 can now be reached in Event E9 from either S34 (new line
>from S34 to S41) or S35
>
>Figure 6-2: Half Duplex State Transition Diagram
>
>State S60 can now be reached in E14 (new line from S14 to S60) from
>either S14 or S36.
>
>best regards,
>
>Greg
>
>[attachment "Prox1_Hailing_Sequence_Update.doc" deleted by Jean-Luc
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