Re: [amsat-bb] July 2001 President's Letter

[Phil Karn <karn@xxxxxxxx>]

>  IMHO it sounds like this bent-pipe transponder with no regeneration
>is much like an SSB transponder and actually it would be possible to
>transmit other kind of signals that would happily be downlinked!?!?

I propose that the transponder hard-limits, as this can greatly
increase DC-RF conversion efficiency. This means it would not be very
useful for SSB because of the severe intermodulation distortion.  It
will be suitable only for one signal at a time, and only when this
signal has constant (or nearly constant) envelope. That's what
dictates that the access mode be TDMA and the modulation mode be PSK
or MSK.

>  Anyway I would be very happy to know what are the main ideias in terms of 
>what users should be able to do with this TDMA system, because actually I 
>think we have spoken little about it :-)

The actual service provided by the system would be IP (internet
protocol) with multicast support. This would directly support
interactive multimedia conferencing tools such as "rat"; see
http://www-mice.cs.ucl.ac.uk/multimedia/software/

--Phil

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