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

[Ed Greenberg]

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.