[Sls-rfm] [Sls-slp] Table form of Prox-1 Phy Layer

Thu Mar 31 18:26:58 UTC 2005

Ed,
I like your wise words. I would add that what we are building is for the
coming 20 years; we must make sure that we make optimal use of the system
potentialities. If we were to introduce lousy requirements, no doubts that
CCSDS would loose part of its credibility. We can't take such a risk. This
400 MHz system is already rather capacity-limited; hence we MUST make the
best out of it.

best regards
Jean-Luc Gerner
TEC-ETT
Tel: +31 71 565 4473

                      Ed Greenberg                                                                                                      
                      <egreenbe at jpl.nasa.gov         To:      thomas.c.jedrey at jpl.nasa.gov, "'Matthew Cosby'"                           
                      >                              <MCosby at space.qinetiq.com>, sls-slp at mailman.ccsds.org                              
                      Sent by:                       cc:      adstanton at keltik.co.uk, adstanton at space.qinetiq.com,                      
                      sls-slp-bounces at mailma         SJKynaston at space.qinetiq.com, "'Dennis Lee'" <Dennis.K.Lee at jpl.nasa.gov>,          
                      n.ccsds.org                    Charles.D.Edwards at jpl.nasa.gov, Eric.Schwartzbaum at jpl.nasa.gov,                    
                                                     David.J.Bell at jpl.nasa.gov                                                          
                                                     Subject: RE: [Sls-rfm] [Sls-slp] Table form of Prox-1 Phy Layer                    
                      24/03/2005 20:44                                                                                                  

Gentlemen,  We are all trying to get to a Standard that will provide
service to all any agencies transceiver.  I think that the problem may be
related to the generalization of the specification.  The real variations
are related to the selected data rate and the non-integer divisor.  Can we
identify the symbol to symbol variance at the specific Prox-1 rates so that
we can a) determine if these are workable or not,  and if they are workable
then we can try to define them in a manner that is rate specific so we can
proceed.

Ed

At 10:27 AM 3/24/2005 -0800, Thomas Jedrey wrote:
>Matthew,
>
>A symbol to symbol to symbol variation was included.
>
>Your comments on the decision to use a non-integer divisor are correct in
>that it was a program decision to use this.  Unfortunately this is not a
>negotiable point since this form of the radio will be providing network
>support at Mars for the next 20 years or so.  So any design expecting
>support from the NASA Mars network assets will have to be compatible with
>these specifications - regardless of whether they are included in the prox-1
>specification or not.
>
>Thomas C. Jedrey
>Supervisor, Wireless Communications Group
>Jet Propulsion Laboratory
>Phone: 818-354-5187
>Fax: 818-354-6825
>
>
>-----Original Message-----
>From: Matthew Cosby [mailto:MCosby at space.qinetiq.com]
>Sent: Thursday, March 24, 2005 8:26 AM
>To: sls-slp at mailman.ccsds.org
>Cc: David.J.Bell at jpl.nasa.gov; Eric.Schwartzbaum at jpl.nasa.gov;
>Thomas.C.Jedrey at jpl.nasa.gov; Dennis Lee; Charles.D.Edwards at jpl.nasa.gov;
>SJKynaston at space.qinetiq.com; adstanton at keltik.co.uk;
>adstanton at space.qinetiq.com
>Subject: [Sls-rfm] [Sls-slp] Table form of Prox-1 Phy Layer
>
>Greg,
>
>here are the BNSC responses to the new pink sheets...
>
>See you in Athens.
>
>Matt.
>
>We would like to voice our concerns regarding this new pink sheets for the
>data rate stability for Proximity-1. These concerns have been developed in
>consultation with engineers at QinetiQ (Steve Kynaston, Dai Stanton and
>myself) who have been responsible for several baseband and RF CCSDS
>systems, including 2 implementations of Proximity 1.
>
>We can't accept a change to a recommendation just because a single
>implementation cannot meet the current specification. The reason why
>Electra could not meet this requirement is due to a design decision not
>because the specification is too stringent. Making this type of change has
>serious knock-on interoperability issues.
>
>The correct cause of action would be for the Electra implementers to issue
>a waiver, to their customers, indicating that they don't meet the current
>Proximity-1 specification. We should not accommodate in the recommendation
>a symbol-to-symbol timing deviation that could lead to, at best, large
>implementation losses in the bit synchroniser and, at worst, a total
>inability of a bit synchroniser to track the incoming data.
>
>We believe that the modifications made to the recommendation at the Autumn
>2004 meeting have severely compromised interoperability between orbiters
>and landers (both extant and planned) by not specifying a symbol-to-symbol
>frequency deviation. The current form of words and, to a greater extent,
>the statements in the pink sheets allow for pathologically behaved baseband
>implementations which would be impossible to decode. (E.g. a waveform which
>had a symbol 99 bit periods long followed by 99 symbols squeezed into a
>single period). We do not believe that it is prudent to issue a
>recommendation which does not provide enough rigor to guarantee
>orbiter/lander interoperability at the bit synchronisation level.
>
>
>
>------------------------------------------------
>Matthew Cosby
>Digital & Embedded Technology,
>Space Department,
>Arthur C Clarke Building,
>QinetiQ Ltd,
>Cody Technology Park,
>Farnborough,
>Hants, UK.
>GU14 0LX.
>
>Tel:            +44 (0)1252 396313
>Pager:  +44 (0)7659 130547
>------------------------------------------------
>e-mail  : MCosby at space.QinetiQ.com
>WWW : http://www.QinetiQ.com
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Progress is impossible when you always do things the way they have always
been done.

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