[Ground-station] UI for SDR

Phil Karn karn at ka9q.net
Sat Jun 30 16:23:12 EDT 2018


On 6/28/18 08:14, Michelle Thompson via Ground-Station wrote:
> Douglas (and all),
> 
> What are your thoughts on a UI design for IP multicast-based SDR? 
> 
> The distributed and flexible nature would seem to be something that
> should come through. 
> 
> I think there's broad agreement about panadapter+waterfall being the
> very best UI for narrowband signals of any type. 

Agreed.

> 
> Is there something as compelling for wideband digital?

Wideband signals are really too specialized to give a general answer. If
we're trying to build something like an Internet, then standard Internet
network monitoring and management tools would be appropriate.

But what levels are you interested in? If you're interested in the
physical layer, you'll want to see physical layer stuff like RSSI, noise
and interference levels, bit error rates, retransmission rates,
modulation and coding scheme (MCS) adapatations over time, etc.

At higher levels you can use standard Internet packet tools like
Wireshark (which can decode 802.11 control packet headers if they're
available from the hardware).

I recently bought a bunch of Ubiquiti access points that come with their
own management package called "UniFi". I was reluctant at first since
it's proprietary to them, but it looks fairly nice. You run it on a
local system (including Linux) and talk to it with a web browser. Among
its utilities is a way to command an access point to do an RF survey and
plot local activity as measurements of signal strength and intensity (%
of time busy) vs frequency.

Soapbox time....

I would like IP (and IPv6) multicast to be a central feature of any
large-scale ham Internet that we build. I think it's an absolute natural
for traditional ham radio applications, especially nets and roundtables.

A *lot* of work went into IP multicasting about 20 years ago yet it's
largely stillborn in the public Internet. It *is* heavily used in some
walled gardens such as AT&T U-verse and some corporate Internets. The
closest approximation to what hams might already know is a DMR
"talkgroup", which is a very pale imitation of what's possible with IP
multicast.

My baseline multicast application for many years has been a tactical
digital voice net. I've been thinking about this ever since 9/11 when I
heard about how many first responder lives were lost to the
communications failures within the WTC towers. Today I *know* we could
build a very effective prototype using just RPis and USB headsets, and
we could extend it into a much larger network.

Here's where I think hams could still make a significant contribution to
the state of the art. We could basically do what Motorola should have
done years ago, except that they're such a monopoly in the public safety
radio business that they've had no incentive to innovate. Our advantage
as hams is that we don't need a financial incentive to do that; it comes
naturally. That's why we were playing with TCP/IP over radio in the mid
1980s, long before the world saw it coming.

Phil



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