[Sls-slp] CCSDS Proximity-1 default hailing parameters/over the air directive set for Lunar

Wed Mar 27 13:07:23 UTC 2024

Dear all,

This email to confirm that the LP ICD symbol rate table match with the Prox1 standard and I would like to add a few points of clarification.

First, the tables enable a direct comparison of LDPC rate ½ and it works fine (see check). The same principle of symbol rate to data rate matching has been used by LP:

LP ICD

CCSDS Prox-1

check
Prox-1 Coded Symbol Rates
Prox-1 LDPC r=2/3 computed data rates (Rd) [b/s]
LDPC r=1/2 computed data rates (Rd) [b/s]

Prox-1 Convolutionally Coded Data Rates (Rd)
Prox-1 LDPC conputed data rates (Rd)

(Rcs)
Rd = 0.65979 Rcs
Rd = 0.48485 Rcs

 Rd = 0.5 Rcs
 Rd = 0.48484 Rcs

1000
N/A
N/A

N/A
N/A

2000
1319.587629
969.6969697

1000
969.6969697

TRUE
4000
2639.175258
1939.3939394

2000
1939.393939

TRUE
8000
5278.350515
3878.7878788

4000
3878.787879

TRUE
16000
10556.701031
7757.5757576

8000
7757.575758

TRUE
32000
21113.402062
15515.1515152

16000
15515.15152

TRUE
64000
42226.804124
31030.3030303

32000
31030.30303

TRUE
128000
84453.608247
62060.6060606

64000
62060.60606

TRUE
256000
168907.216495
124121.2121212

128000
124121.2121

TRUE
512000
337814.432990
248242.4242424

256000
248242.4242

TRUE
1024000
675628.865979
496484.8484848

512000
496484.8485

TRUE
2048000
1351257.731959
992969.6969697

1024000
992969.697

TRUE
4096000
2702515.463918
1985939.3939394

2048000
1985939.394

TRUE

The ratios are the following:

  *   LDPC 2/3 = 4096/(4096*3/2+64)
  *   LDPC 1/2 = 1024/(1024*2+64)

Then, I believe there were several points that made it unnecessarily complex:

  *   I confirm we should all talk about coded symbol rate, this is the actual fixed reference value for each line (Rcs),
  *   The Prox1 directives of the current datalink standard are mentioning TX data rates or RX data rates and not symbol rates, which I believe is not adequate,
  *   The LP ICD explanation is a bit complex for something that is, in the end, rather simple when simply using the reference table and clearer if the first column would mention Rcs and not Rd as currently.

A typo in Prox1:  The Prox1 symbol rate reference table is mentioning a LDPC ½ ratio of 0.48484, whereas it should be 0.48485 (the next number is a '8')

With best regards,

[cid:image001.png at 01DA804E.364BE980]
Brice Dellandrea
Lunar Pathfinder System Engineer  & Moonlight User Interface Engineer
Commercialisation & Innovation Team (HRE-XI)
Directorate of Human Spaceflight & Robotic Exploration
European Space Research and Technology Centre (ESTEC)
Keplerlaan 1, PO Box 299
NL-2200 AG Noordwijk, The Netherlands

From: Kazz, Greg (US 312B) <greg.j.kazz at jpl.nasa.gov>
Sent: Monday, March 25, 2024 9:55 PM
To: Kazz, Greg (US 312B) via SLS-SLP <sls-slp at mailman.ccsds.org>; Ben Schwarz <BSchwarz at sstl.co.uk>; plobell at sstl.co.uk; Fadl, Ahmed M. (GSFC-8500) <ahmed.m.fadl at nasa.gov>; Shihabi, Mazen M (US 337K) <mshihabi at jpl.nasa.gov>; ymarashi at vulcanwireless.com; gsignori at dscosys.space; Brice Dellandrea <Brice.Dellandrea at esa.int>; Lee, Dennis K (US 332G) <dennis.k.lee at jpl.nasa.gov>
Subject: CCSDS Proximity-1 default hailing parameters/over the air directive set for Lunar

Hi All,

Attached are the current versions of two TBD normative annexes that the CCSDS SLP WG is trying to finalize at the upcoming Spring CCSDS meetings in Washington, D.C. during the last week of April/Beginning of May 2024.

Please let me know if you have any comments/concerns regarding this material.
(I will also place it into the SLP WG folder on the CCSDS CWE as well. (For those of you who are new to CCSDS, once you get the invitation to join the WG, you will also be able to access these files and future ones that way as well.)

The default hailing parameters provides the minimum  interoperability for two separate enterprises: 1) Mars at UHF and 2) Lunar at S-band.

The over the air directive set introduces the "new" set of directives for lunar ops called SPDU Type 4. There was a question at our meeting today along the lines of do these directives provide enough operability concerning a negotiated link establishment process? After examining the directives, please let me know if you think they don't and why?

Some notes below:

  *   The SLP WG has defined up to 32 physical channels slots in the directives (more than we currently need but it provides room to grow.)
  *   All rates are given as Symbol Rates and NOT as data rates. Note that the user can select the specific symbol rate they desire unlike the approach used for Mars.
  *   I will add those folks to the SLP WG above in the distribution list once I find the time to do so.
  *   Mod Index values still need to be defined

Thanks again for a very productive meeting and best regards,

Greg

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