<span style=" font-size:10pt;font-family:sans-serif">Dear Peter,</span>
<br><span style=" font-size:10pt;font-family:sans-serif">
a friend of mine uses to say that "if you ask
for advice to a sufficient number of persons, at least one will eventually
recommend you what you wanted to do".</span>
<br><span style=" font-size:10pt;font-family:sans-serif">In the same way,
I am sure that looking around for sufficient time we will find the "One
Thousand and One Arabian Layers" book by Shahrazad.</span>
<br>
<br><span style=" font-size:10pt;font-family:sans-serif">I think we shall
ensure consistency in CCSDS and therefore I stick to CCSDS books.</span>
<br><span style=" font-size:10pt;font-family:sans-serif">BTW, I do not
find fully correct stating that <in CCSDS we have “data link” == SDLP
and C&S, and “physical” == RF & Mod and now optical>.</span>
<br><span style=" font-size:10pt;font-family:sans-serif">As the figures
(in my original mail) show the OSI Data Link Layer is indeed split by CCSDS
into two sublayer. Conversely the Physical Layer (1:1 correspondence between
OSI and CCSDS) can be characterised in many ways: RF, Optical, Cable, etc.</span>
<br><span style=" font-size:10pt;font-family:sans-serif">In one case we
have splitting, in the other one we have "characterization (according
to physical characteristics)".</span>
<br>
<br><span style=" font-size:10pt;font-family:sans-serif">Can you please
define what you call <</span><span style=" font-size:11pt;font-family:Calibri">
“normal” CCSDS standards</span><span style=" font-size:10pt;font-family:sans-serif">>?</span>
<br>
<br><span style=" font-size:10pt;font-family:sans-serif">It is true that
in many CCSDS Standards (as e.g. the Space Data Link Protocols, but not
only), in order to conserve bandwidth on the space link, some parameters
associated with the given standard are handled by management rather than
by inline communications protocol. </span>
<br><span style=" font-size:10pt;font-family:sans-serif">Usually there
is a mixing of managed and inline parameters. Just to mention an example,
</span><a href=https://public.ccsds.org/Pubs/732x0b3e1.pdf><span style=" font-size:10pt;color:blue;font-family:sans-serif">https://public.ccsds.org/Pubs/732x0b3e1.pdf</span></a><span style=" font-size:10pt;font-family:sans-serif">
uses in the Frame Header a Virtual Channel identifier and even a "Signaling
Field".</span>
<br><span style=" font-size:10pt;font-family:sans-serif">Actually, USLP
( </span><a href=https://public.ccsds.org/Pubs/732x1b1.pdf><span style=" font-size:10pt;color:blue;font-family:sans-serif">https://public.ccsds.org/Pubs/732x1b1.pdf</span></a><span style=" font-size:10pt;font-family:sans-serif">
) goes further and - as you know - Greg proudly remarks that USLP increases
the number of signalling fields.</span>
<br>
<br><span style=" font-size:10pt;font-family:sans-serif">Indeed the </span><span style=" font-size:11pt;font-family:Calibri"> diagrams
I sent do not really reflect any of the details added by the "VCM
family" because it was not the scope of those figures.</span>
<br><span style=" font-size:11pt;font-family:Calibri">Other diagrams in
the various standards clarify the details that have nothing to do with
layering.</span>
<br>
<br><span style=" font-size:11pt;font-family:Calibri">My conclusion is
that all CCSDS Standards are "normal" CCSDS Standards and include
both managed parameters and inline parameters.</span>
<br><span style=" font-size:11pt;font-family:Calibri">Increasing the inline
parameters - as USLP shows just to give an example outside coding and modulation
fields - increases complexity but I am not aware of a CCSDS mandate for
only keeping simple things and/or stopping progress.</span>
<br><span style=" font-size:11pt;font-family:Calibri">The increased complexity
(in general) is a price to pay for modernity and efficiency and - luckily
- a price we can pay thanks to new technologies as e.g. LDPC codes
- invented by Gallager ( </span><a href=https://en.wikipedia.org/wiki/Robert_G._Gallager><span style=" font-size:11pt;color:blue;font-family:Calibri">https://en.wikipedia.org/wiki/Robert_G._Gallager</span></a><span style=" font-size:11pt;font-family:Calibri">
) in 1960 when their implementation was unrealistic for the technology
available at that time - do show.</span>
<br>
<br><span style=" font-size:11pt;font-family:Calibri">This closes my discussions
on layering.</span>
<br><span style=" font-size:11pt;font-family:Calibri">Otherwise I confirm
my statement: </span><span style=" font-size:10pt;font-family:Arial">I
still need to digest all the aspects of your message, however I can ensure
that SLS (with proper coordination) will try to provide some punctual technical
comments on the individual items.</span><span style=" font-size:11pt;font-family:Calibri">
</span>
<br>
<br><span style=" font-size:11pt;font-family:Calibri">Best regards</span>
<br>
<br><span style=" font-size:11pt;font-family:Calibri">Gippo</span>
<br>
<br>
<br>
<br>
<br><span style=" font-size:9pt;color:#5f5f5f;font-family:sans-serif">From:
</span><span style=" font-size:9pt;font-family:sans-serif">"Shames,
Peter M (US 312B)" <peter.m.shames@jpl.nasa.gov></span>
<br><span style=" font-size:9pt;color:#5f5f5f;font-family:sans-serif">To:
</span><span style=" font-size:9pt;font-family:sans-serif">"Gian.Paolo.Calzolari@esa.int"
<Gian.Paolo.Calzolari@esa.int></span>
<br><span style=" font-size:9pt;color:#5f5f5f;font-family:sans-serif">Cc:
</span><span style=" font-size:9pt;font-family:sans-serif">"SEA-SA"
<sea-sa@mailman.ccsds.org>, "SLS - Space Link Services Area"
<sls@mailman.ccsds.org></span>
<br><span style=" font-size:9pt;color:#5f5f5f;font-family:sans-serif">Date:
</span><span style=" font-size:9pt;font-family:sans-serif">03-03-21
23:08</span>
<br><span style=" font-size:9pt;color:#5f5f5f;font-family:sans-serif">Subject:
</span><span style=" font-size:9pt;font-family:sans-serif">Re:
[EXTERNAL] It is a smaller sandwich: [Sea-sa] Background materials for
today's SEA-SA SCCS-ARD discussion</span>
<br>
<hr noshade>
<br>
<br>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:11pt;font-family:Calibri">Hi
Gippo,</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:11pt;font-family:Calibri"> </span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:11pt;font-family:Calibri">We
welcome the inputs from the SLS Area in ensuring that what gets reflected
in the SCCS-ARD is accurate. We use as sources for all of these materials
the published standards (and the draft ones that are sufficiently mature,
as noted).</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:11pt;font-family:Calibri"> </span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:11pt;font-family:Calibri">As
for “how many layers”, that sort of depends on how you count them. We
all know that the ISO BRM only lists “data link - layer 2” and “physical
- layer 1”. But in CCSDS we have “data link” == SDLP and C&S,
and “physical” == RF & Mod and now optical. The fact that
C&S and RF&Mod both include an “and” reflects that these are
themselves compound entities, with “sub-layers” of sorts. And we
are all aware that SDLP frame lengths get bound to C&S block lengths
in special ways.</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:11pt;font-family:Calibri"> </span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:11pt;font-family:Calibri">Furthermore,
in all of the “normal” CCSDS standards the approach that has consistently
been taken is to use “managed parameters” in many cases and thereby require
that the two ends of the comm link, sender and receiver, coordinate ahead
of time and choreograph communications assets for pointing as well as choreograph
data rate changes and changes to “communications modes”, such as low
rate, high rate, emergency mode, one-way, two-way, etc. It all gets
pre-planned and “baked in” to the communications pass. There is
no signaling aside from whatever gets transmitted.</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:11pt;font-family:Calibri"> </span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:11pt;font-family:Calibri">But
in the SCCC and DVB-S2, and now the VCM too, we introduce a new signaling
mechanism, a new physical layer “framing” approach, and with ACM a feedback
loop from receiver back to sender. The diagrams you sent do not really
reflect any of this added detail or complexity, which is why we produced
the more detailed diagrams that show these features, which were extracted
from the standards themselves. It would be useful to have your team
review these more accurate diagrams and make sure that they correctly reflect
the all of the features, and their ordering and connections, that are present
in these standards. I find them to be much more useful than those
block diagrams that leave out all of these details.</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:11pt;font-family:Calibri"> </span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:11pt;font-family:Calibri">Is
that something you can do?</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:11pt;font-family:Calibri"> </span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:11pt;font-family:Calibri">We
can argue over how many “layers”, relative to the ISO BRM, but it seems
pretty clear that CCSDS has for years been treating L1 and L2 as having
sub-layers. And it seems pretty clear that these newer, more complicated,
standards introduce even more sub-layers, as well as some new “cross layer”
management and control “sub-layers” that live “on the side” and control
behavior of these other sub-layers.</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:11pt;font-family:Calibri"> </span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:11pt;font-family:Calibri">It
would be good to get your feedback to make sure that we represent all of
this accurately.</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:11pt;font-family:Calibri"> </span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:11pt;font-family:Calibri">Thanks,
Peter</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:11pt;font-family:Calibri"> </span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:11pt;font-family:Calibri"> </span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:12pt;font-family:Calibri"><b>From:
</b>Gian Paolo Calzolari <Gian.Paolo.Calzolari@esa.int><b><br>
Date: </b>Wednesday, March 3, 2021 at 10:18 AM<b><br>
To: </b>Peter Shames <peter.m.shames@jpl.nasa.gov><b><br>
Cc: </b>SEA-SA <sea-sa@mailman.ccsds.org>, SLS - Space Link Services
Area <sls@mailman.ccsds.org><b><br>
Subject: </b>[EXTERNAL] It is a smaller sandwich: [Sea-sa] Background materials
for today's SEA-SA SCCS-ARD discussion</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:11pt;font-family:Calibri"> </span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:10pt;font-family:Arial">Dear
Peter,</span><span style=" font-size:11pt;font-family:Calibri"> </span><span style=" font-size:10pt;font-family:Arial"><br>
I must say that I am quite puzzled by this
mail.</span><span style=" font-size:11pt;font-family:Calibri"> </span><span style=" font-size:10pt;font-family:Arial"><br>
I still need to digest all the aspects of your message, however I can ensure
that SLS (with proper coordination) will try to provide some punctual technical
comments on the individual items.</span><span style=" font-size:11pt;font-family:Calibri">
<br>
</span><span style=" font-size:10pt;font-family:Arial"><br>
Here, after a check with SLS colleagues, I want to comment on your statement
about the </span><span style=" font-size:11pt;font-family:Calibri">“3-layer
sandwich” </span><span style=" font-size:10pt;font-family:Arial">.</span><span style=" font-size:11pt;font-family:Calibri">
</span><span style=" font-size:10pt;font-family:Arial"><br>
Indeed that sandwich is not so big as you claim.</span><span style=" font-size:11pt;font-family:Calibri">
<br>
</span><span style=" font-size:10pt;font-family:Arial"><br>
Actually all the following documents</span><span style=" font-size:11pt;font-family:Calibri">
</span><span style=" font-size:11pt;color:blue;font-family:Calibri"><u><br>
</u></span><a href="https://urldefense.us/v3/__https:/public.ccsds.org/Pubs/131x2b1e1.pdf__;!!PvBDto6Hs4WbVuu7!demyENKGsE_7PJJrR6SbeOXkhtjiGFopt8LGoDr7ESP8cpphnhgTNO8cfJxgRGhPQApStP0N$"><span style=" font-size:10pt;color:blue;font-family:Arial"><u>https://public.ccsds.org/Pubs/131x2b1e1.pdf</u></span></a><span style=" font-size:11pt;font-family:Calibri">
</span><span style=" font-size:11pt;color:blue;font-family:Calibri"><u><br>
</u></span><a href="https://urldefense.us/v3/__https:/public.ccsds.org/Pubs/131x3b1.pdf__;!!PvBDto6Hs4WbVuu7!demyENKGsE_7PJJrR6SbeOXkhtjiGFopt8LGoDr7ESP8cpphnhgTNO8cfJxgRGhPQHLhWGkA$"><span style=" font-size:10pt;color:blue;font-family:Arial"><u>https://public.ccsds.org/Pubs/131x3b1.pdf</u></span></a><span style=" font-size:11pt;font-family:Calibri">
</span><span style=" font-size:11pt;color:blue;font-family:Calibri"><u><br>
</u></span><a href="https://urldefense.us/v3/__https:/public.ccsds.org/Pubs/431x0b1.pdf__;!!PvBDto6Hs4WbVuu7!demyENKGsE_7PJJrR6SbeOXkhtjiGFopt8LGoDr7ESP8cpphnhgTNO8cfJxgRGhPQEFDXIjo$"><span style=" font-size:10pt;color:blue;font-family:Arial"><u>https://public.ccsds.org/Pubs/431x0b1.pdf</u></span></a><span style=" font-size:11pt;font-family:Calibri">
<br>
</span><span style=" font-size:10pt;font-family:Arial"><br>
clearly state that "This Recommended Standard covers the functions
of both the Synchronization and Channel Coding Sublayer and the Physical
Layer"; i.e. the layers combined are two (or let's say 1 and half
as one layer and one sublayer are combined).</span><span style=" font-size:11pt;font-family:Calibri">
</span><span style=" font-size:10pt;font-family:Arial"><br>
They all also show this (even with some minor differences) in their "Figure
2-1: Relationship with OSI Layers" showing together the</span><span style=" font-size:11pt;font-family:Calibri">
</span><span style=" font-size:10pt;font-family:Arial"><br>
1) Synchronization and Channel Coding Sublayer that provides methods of
synchronization and channel coding for transferring Transfer Frames over
a space link and the <br>
2) Physical Layer that provides the RF and modulation methods for transferring
a stream of bits over a space link in a single direction</span><span style=" font-size:11pt;font-family:Calibri">
<br>
</span><span style=" font-size:10pt;font-family:Arial"><br>
For reference the three figures are attached as snapshots.</span><span style=" font-size:11pt;font-family:Calibri">
<br>
</span><span style=" font-size:10pt;font-family:Arial"><br>
Best regards</span><span style=" font-size:11pt;font-family:Calibri"> <br>
</span><span style=" font-size:10pt;font-family:Arial"><br>
Gian Paolo </span><span style=" font-size:11pt;font-family:Calibri"><br>
<br>
<br>
</span><img src=cid:_1_0B68C3280B68AE48003563FAC125868E style="border:0px solid;"><img src=cid:_1_0B68C55C0B68AE48003563FAC125868E style="border:0px solid;"><span style=" font-size:10pt;font-family:Arial">
</span><img src=cid:_1_0B68C7A80B68AE48003563FAC125868E style="border:0px solid;"><span style=" font-size:11pt;font-family:Calibri"> <br>
<br>
</span><span style=" font-size:9pt;color:#5f5f5f;font-family:Arial"><br>
From: </span><span style=" font-size:9pt;font-family:Arial">"Shames,
Peter M\(US 312B\) via SEA-SA" <sea-sa@mailman.ccsds.org></span><span style=" font-size:11pt;font-family:Calibri">
</span><span style=" font-size:9pt;color:#5f5f5f;font-family:Arial"><br>
To: </span><span style=" font-size:9pt;font-family:Arial">"SEA-SA"
<sea-sa@mailman.ccsds.org></span><span style=" font-size:11pt;font-family:Calibri">
</span><span style=" font-size:9pt;color:#5f5f5f;font-family:Arial"><br>
Date: </span><span style=" font-size:9pt;font-family:Arial">02-03-21
23:37</span><span style=" font-size:11pt;font-family:Calibri"> </span><span style=" font-size:9pt;color:#5f5f5f;font-family:Arial"><br>
Subject: </span><span style=" font-size:9pt;font-family:Arial">[Sea-sa]
Background materials for today's SEA-SA SCCS-ARD discussion</span><span style=" font-size:11pt;font-family:Calibri">
</span><span style=" font-size:9pt;color:#5f5f5f;font-family:Arial"><br>
Sent by: </span><span style=" font-size:9pt;font-family:Arial">"SEA-SA"
<sea-sa-bounces@mailman.ccsds.org></span><span style=" font-size:11pt;font-family:Calibri">
</span></p>
<div align=center>
<hr noshade></div>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:11pt;font-family:Calibri"><br>
</span><span style=" font-size:10pt;font-family:Arial"><br>
[attachment "431x1b0_CESG_Approval.pdf" deleted by Gian Paolo
Calzolari/esoc/ESA] </span></p>
<br><span style=" font-size:12pt">Dear SCCS-ARD sub-team,</span>
<br><span style=" font-size:12pt"> </span>
<br><span style=" font-size:12pt">During today’s SEA-SA SCCS-ARD discussion
we spent quite a period of time discussing the challenges in create a reasonably
compact, and also accurate, table that reflects the currently documented
set of configurations that are made available by the suite of space data
link, coding, synchronization, modulation, RF (and optical), and physical
layer signaling standards. There are many situations where there
is no one, simple, statement, or even set of statements, that can be made.
We have had to resort to a tabular presentation, Table 6-8 in Sec
6 on protocols, to address this. A copy of this table is attached,
along with the “cheat sheet” of notes that encode the cells in this table.</span>
<br><span style=" font-size:12pt"> </span>
<br><span style=" font-size:12pt">Any standards that are expected to come
into being within the next 6-12 months, but that are not yet final, are
highlighted in yellow. We hope these are final before we publish
this document, but all of those dates are still rather uncertain.</span>
<br><span style=" font-size:12pt"> </span>
<br><span style=" font-size:12pt">Note that uplink is separate from downlink,
that RF coding and modulation is separate from optical coding and modulation,
and that SCCC and DVB-S2 (which both contain coding, modulation, and physical
layer signaling in a single standard) are separated from the “normal”
CCSDS standards that break these into three separate layers. The
new Variable Coding and Modulation (VCM) spec that is now in progress is
also shown as a separate layer. This VCM spec is related to the “bottom”
parts of the DVB and SCCC specs, but it is different from them in distinct
ways. </span>
<br><span style=" font-size:12pt"> </span>
<br><span style=" font-size:12pt">It became clear during discussion that
most of those on the call were unfamiliar with the details and complexities
represented in this table. Furthermore, most are unfamiliar with
the complexities inherent in the “3-layer sandwich” that SCCC and DVB
present, and with how they compare with the “normal” CCSDS link layer,
coding, synch, modulation, physical layer and RF stack. I have attached
a presentation that some of us constructed in order to make sure that we
understood what those relationships are. It is named “SEA high rate
comm issue 1Mar21” and is attached here. This is a statement of
the recent issues and also a set of diagrams comparing these different
protocol sets. It does not address optical comm.</span>
<br><span style=" font-size:12pt"> </span>
<br><span style=" font-size:12pt">It should be noted that the “bottom”
part of the DVB and SCCC specs includes a specialized set of physical layer
signaling mechanisms. These are not present in normal CCSDS protocol
stacks, where any choices that are made for different coding, synchronization,
and modulation combinations are made “by management”. That phrase
“by management” means that the mission manages these choices manually,
outside of the protocols themselves, that the protocol layers contain no
“signals” as to which choices were made, and that any changes to the
coding and modulation must be agreed to and managed out of band, by pre-agreement.
</span>
<br><span style=" font-size:12pt"> </span>
<br><span style=" font-size:12pt">In the DVB and SCCC, and in the new draft
CCSDS VCM spec (CCSDS 431.1-b-1) which is attached here as a CESG draft
spec, a physical layer signaling mechanism is introduced. VCM is
defined as “<b>variable coded modulation, VCM</b>: A method to adapt the
transmission scheme to channel conditions following a predetermined schedule.
”. This includes two separate physical layer structures: 1)
the “Pilot Symbols” and 2) the encoded and modulated data symbols. The
CCSDS 431.1 spec describes two different VCM “types”. Type 1 uses
the DVB-S2 VCM pilot symbol and data symbol length approach, Type 2 uses
the SCCC VCM pilot symbol and data symbol length approach. These
pilot symbols are, in both cases, just short blocks of 7 bits, protected
by a linear code and BPSK modulation (see attached Table from Annex E).
Five of these bits are used to identify one of the 32 possible sets
of code and modulation pairs that are applied to the encoded and modulated
symbols that follow the pilot. </span>
<br><span style=" font-size:12pt"> </span>
<br><span style=" font-size:12pt">Where these DVB Type 1, SCCC Type 2,
and CCSDS Type 1 or 2 schemes differ is in the length of the symbol strings
and the sets of code/modulation pairs that are allowed. </span>
<ul>
<li><span style=" font-size:11pt;font-family:Calibri">DVB-S2 has its own
set shown in Table 3-4. It allows different code rates, from 1 /
4 (0.25) up to 9 / 10 (0.9), different input lengths from 2992 up to 58112
bits, different modulations (QPSK, 8-PSK, 16 & 32-APSK) and its own
set of DVB-S2 codes that are patented. </span>
<li><span style=" font-size:11pt;font-family:Calibri">SCCC has its own
set shown in Table 3-3. It allows different code rates, from 0.36
up to 0.9, different input lengths from 5758 up to 43678 bits, the same
set of modulations (QPSK, 8-PSK, 16 & 32-APSK) and its own set of SCCC
codes that are patented. </span>
<li><span style=" font-size:11pt;font-family:Calibri">The CCSDS VCM has
its own set shown in Table 3-2. It allows different (CCSDS standard)
code rates, from 1 / 6 (0.16) up to 223/255 (0.875), different (CCSDS standard)
input lengths from 1748 up to 16384 bits, the same set of modulations plus
BPSK (BPSK, QPSK, 8-PSK, 16 & 32-APSK) and the standard LDPC codes.
</span>
<br><span style=" font-size:12pt"> </span></ul><span style=" font-size:11pt;font-family:Calibri">You
can see that these are similar, and that the modulation set largely overlaps,
but they are different. In all cases specialized equipment will be
needed in the RF front ends to handle the pilot symbols and the continually
changing coding and modulation . The other difference is that the
CCSDS VCM expects to signal a pre-planned set of code & modulation
changes, but the SCCC and DVB-S2 also include adaptive coding and modulation
(ACM), which uses signals sent back from the receiver to the sender. To
quote from SCCC, CCSDS 131x2b1d1, Sec 3.2.7: </span>
<br><span style=" font-size:12pt;color:#424282;font-family:TimesNewRomanPSMT">NOTE
– </span>
<br><span style=" font-size:12pt;color:#424282;font-family:TimesNewRomanPSMT">Changes
of the value of the information block size </span><span style=" font-size:12pt;color:#424282"><i>K
</i></span><span style=" font-size:12pt;color:#424282;font-family:TimesNewRomanPSMT">are
done by a system to adjust the modulation and coding schemes. This is achieved
through, e.g., one of the following approaches: the ground receiver provides
the signal quality estimation (or prediction) through a feedback channel
(e.g., via telecommand) or the change of modulation and coding schemes
is pre-scheduled for each satellite pass based on geometrical information
(elevation angle). </span>
<br><span style=" font-size:12pt">So the SCCC may use a feedback loop,
but no specific protocol appears to be specified for this. The DVB-S2
standard, as adapted for CCSDS, makes essentially the same statement.
The full ETSI DVB-S2 spec, however, defines an actual feedback protocol
that is, in my opinion, only of use over a near Earth (or at least a “local”)
communications path where the RTLT is sufficiently short to allow requests
for data rate changes to be responded to. This is not appropriate
for use in deep space where the RTLT may be measures in 10’s of minutes
or tens of hours. They also bring substantial added complexity which,
in the general case, may not be worth the added cost of engineering, testing,
etc unless the mission is a) in a near Earth orbit, and b) can make use
of available commercial parts.</span>
<br><span style=" font-size:12pt"> </span>
<br><span style=" font-size:12pt">As I suggested during the webex, I think
we must treat the following groups of standards separately, because to
do otherwise will overly complicate the core of the CCSDS standard suite,
that I estimate meets 95% of the users.</span>
<br><span style=" font-size:12pt"> </span>
<br><span style=" font-size:10pt;font-family:Arial">1.
</span><span style=" font-size:12pt">The “CCSDS standard” suite
of link layer, coding, synchronization, modulation, and RF standards</span>
<br><span style=" font-size:10pt;font-family:Arial">2.
</span><span style=" font-size:12pt">A subsection on the Optical
coding and modulation standards that slot in underneath the normal link
layer protocols, along with a brief description</span>
<br><span style=" font-size:10pt;font-family:Arial">3.
</span><span style=" font-size:12pt">A separate subsection on the
VCM and the associated SCCC and DVB-S2 “omnibus” standards that replace
the standard CCSDS coding, synchronization, modulation and add physical
layer signaling.</span>
<br><span style=" font-size:12pt"> </span>
<br><span style=" font-size:12pt">If anyone has issues with this approach
please bring them up now. I think this is the only sensible way to
handle this issue of these very different approaches to the lower layer
protocols.</span>
<br><span style=" font-size:12pt"> </span>
<br><span style=" font-size:12pt">Thanks, Peter</span>
<br><span style=" font-size:12pt"> </span>
<br><span style=" font-size:12pt"> </span>
<br><span style=" font-size:12pt"> </span><span style=" font-size:10pt;font-family:Courier New">_______________________________________________<br>
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<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:10pt;font-family:Arial"><br>
[attachment "SEA High Rate comm issue 1Mar21.pptx" deleted by
Gian Paolo Calzolari/esoc/ESA] [attachment "CCSDS 431 VCM protocol
layers.pdf" deleted by Gian Paolo Calzolari/esoc/ESA] [attachment
"CCSDS 431 VCM pilot pattern.pdf" deleted by Gian Paolo Calzolari/esoc/ESA]
[attachment "CCSDS 431 DVB SCCC pilot approaches.pdf" deleted
by Gian Paolo Calzolari/esoc/ESA] [attachment "SCCS-ARD Table 6-8
Notes 1Mar21.pdf" deleted by Gian Paolo Calzolari/esoc/ESA] [attachment
"SCCS-ARD Table 6-8 proto layer options.pdf" deleted by Gian
Paolo Calzolari/esoc/ESA] </span></p>
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