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Re: DSP software on Sunsat SO-35



> 13 Feb 00 18:40, WB4APR wrote:
> 
>  BB> Similarly, we could VASTLY improve the downlinks of bulk files from
>  BB> our existing pacsats if..... just let everyone pool their captures
>  BB> together.  This would permit a 10 fold improvement in data throughput
>  BB> or more... (unless someone is already doing this)...

Tony Langdon replied:
> This would require the implementation of some form of multicasting, such as
> exists in TCP/IP, and some mechanism to manage who's involved in the sessions
> (such as IGMP does in the TCP/IP world).
> Might be an interesting experiment.

That's what's so neat is that No changes to the satelilte are required.

And on the ground, the software that collects multiple disparate
simultaneous, redundant feeds and distributes a single combined
dupes-removed stream has been in place for years in the APRServe system
written by Steve Dimse.  To see it live, just TELNET to 199.227.86.221.

Yes, you would still need at least one PACSAT station requesting donwloads
in the usual fashion per footprint, but all the other receive-only
stations would simply be providing spacial-diversity reception and pooling
their packets captured with everyone elses.

Since the PACSAT protocol already fully identifies every packet for later
re-construction into contiguous files, there is no need for any change on
the spacecraft...

The APRServe software has been doing this kind of Internet colllection and
distribution for many years... and I think can handle hundreds of
simultaneous connections...  But again, Steve DImse K4HG is the expert...

We invited satellite ops to try it but the best we got was the few MIR
feeds a few years ago because of the simplicity of the no-tune, omni
downlink.   But it is ideal when you have lots of data on the spacecraft
that needs to get down...

de WB4APR, Bob


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