[Sis-csi] Cislunar Section 8

[Adrian J. Hooke]

At 12:17 PM 8/23/2005, Keith Hogie wrote:
>3 - The protocol stack diagram is nice but I'm not sure about the AOS 
>boxes.  Normally AOS is used for data coming down from space.

Not so - the original architecture that was developed for ISS was 
completely symmetric - the AOS frame was intended to be used as either a 
unidirectional or a bi-directional space link protocol. See 
http://public.ccsds.org/publications/archive/701x0b3.pdf page 2-3.

>It also has Reed-Solomon coding on it.  The diagram uses AOS in both 
>directions.  Are we proposing the use of AOS and Reed-Solomon coding both 
>ways.  This would require R/S encoders at ground stations and decoders 
>installed on spacecraft?

The CCSDS space link protocols are cleanly layered: 
http://public.ccsds.org/publications/archive/130x0g1.pdf

In particular, the current AOS Space Link Protocol as defined in:
http://public.ccsds.org/publications/archive/732x0b1.pdf is decoupled from 
its underlying coding layers.

The coding layer that underlies AOS or conventional TM space links is 
defined in: http://public.ccsds.org/publications/archive/131x0b1.pdf and 
note that it is NOT confined to R-S coding. It may be also expected to 
evolve as new codes (such as LDPC) mature.

>   Do we want to get into the details of lower layer protocols to use for 
> two-way links

No; other CCSDS WGs (by charter) take care of these. The Cislunar WG may 
want to form SIGs to correspond with them, though, if the Chairman thinks 
that this is appropriate.

>If this group is not dealing with lower layers, should the diagrams just 
>leave them blank and start with the network layer?

Chris's Section 8.1.1 is clearly identified as an "example". As such, it is 
fully appropriate that it could show a representative set of underlying 
standard protocols. Since there's nothing technically incorrect about the 
diagram, as an example it is probably useful.

Best regards

Adrian J. Hooke
Chairman, CCSDS Engineering Steering Group (CESG)
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