
Delay-Tolerant Networks Might Be the Killer App Ham Radio Needs - DyslexicAtheist
https://faradayrf.com/delay-tolerant-networks-killer-app/
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jvanderbot
I work at JPL and have begun using the ION implementation of DTN as part of a
distributed computing research project. The development of this stack is very
active, and momentum is pretty solid internally. It wouldn't surprise me to
see more use of DTN in the near future. The lead devs are active and
responsive despite being promoted away from front line work most of the time.
Also, this is TRL 8/9, so ION / DTN is pretty stable.

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phaedrus
I looked into this in 2007 - 2008, when I was in college. I was doing a NASA
internship, working on an engineering study of IP communication over deep
space links. However my directive concerned IP protocol specifically. DTN was
an interesting case study to me, but we weren't trying to use the DTN protocol
so I never tried to actually set it up. I thought it was a neat idea, but I
hadn't kept up with developments in that field since then.

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calgoo
I think of this as well, especially when looking towards the future with Mars
colonies etc. However, I see it as a mix of data dumps of the internet as we
know it and some sort of email system as well.

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jvanderbot
I actually think IoT is a great application, as devices become producers, but
also relays for messaging. The use case for this functionality is orbiter
relay, but there's nothing to prevent any moving agent to be a "router" in
DTN, no matter how long it's offline.

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Steltek
Mirror link please? (Oddly Google on Firefox Mobile doesn't appear to offer
cache links)

And IMO, the shot of adrenaline that ham radio needs is for the FCC to take
the gloves off of data modes on HF. 300 baud, are you kidding me? The same RF
bandwidth that analog voice gets to use could deliver magnitudes more as a
digital signal.

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VLM
Its a weird case of legislating good engineering into political law. Its not
needed; should be able to just quote FCC part 97.101(a) "In all respects not
specifically covered by FCC Rules each amateur station must be operated in
accordance with good engineering and good amateur practice"

Google up "digital transmission on fading multipath channels" or similar and
for example there's a nice whitepaper from National

[http://www.ni.com/white-paper/14931/en/](http://www.ni.com/white-
paper/14931/en/)

The ionosphere makes massive incredible multipath distortion causing
intersymbol interference making anything over 100 or so symbols per second
basically broadband noise aka jamming. Even if by some miracle a (short NVIS?)
hop were decodable between hams X and Y, the ionosphere being what it is means
everyone else on the band would be hearing distorted broadband noise.

Most of the work recently (like last 30 years) has been in very low baud rate
systems. From memory, doesn't FT8 run at 5.86 baud? It uses multi channel fsk
and some FEC weirdness to push a remarkable number of bits per symbol.

Like a decade ago I used to talk to people using Olivia mode which runs at
31.25 baud which frankly was too fast for conditions. Olivia also encoded
quite a few bits per symbol. Generally symbol rates (baud rates) have been
dropping while bits/sec has been increasing for a very long time. In the
really old days like RTTY the baud rate was the bits/sec rate so the ratio of
bits/baud was 1, it hasn't been that low in a long time. It was very
frustrating and weird (an annoying!) to watch a waterfall display as multipath
fading drifted thru a band and destroyed just the mark or just the space
carrier of a RTTY signal. 45 baud rtty is probably the highest baud rate
you'll see on HF digital ham radio.

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lightlyused
"Most of the work recently (like last 30 years) has been in very low baud rate
systems. From memory, doesn't FT8 run at 5.86 baud? It uses multi channel fsk
and some FEC weirdness to push a remarkable number of bits per symbol."

It also makes communications possible where normal modes just don't work well.
For example, six meter (50MHz) band contacts where the signal signal level is
extremely weak and the opens very brief.

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Animats
He's re-inventing UUCP.[1]

[1] [https://en.wikipedia.org/wiki/UUCP](https://en.wikipedia.org/wiki/UUCP)

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vvanders
Yeah, yeah everything old is new again.

The one thing I like about faradayrf is they're at least trying. Right now the
state of packet radio is either 1200bps bell tones with no FEC or modern
modulation and on the other end something like FT8 which is incredible but has
almost zero bandwidth and good for only communicating "I heard you".

I'd love to see a more modern packet infrastructure that isn't stuck in the
80s.

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kb1lqc
Spot on ;)

In fact this post was meant to start the discussion you are alluding to. Let's
not reinvent the wheel as so much as take what we have available to us now and
use it combined with some new technology to propel ham radio into modern
communications.

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vvanders
Yeah, I would love to see some modern N-QAM, FEC spec make it's way into the
APRS space. The number of times I see 144.390 key up at S8+ and no packet has
to be at least 50% of the time.

Some of the stuff that happens in DMR space is pretty cool, even simple TDMA
opens up so many possibilities. You could do Voice+APRS at the same time over
the modern repeater network. For instance we've got BawFaw that covers most of
SW Washington, would be awesome to be able to run something like that for
packet radio.

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zeckalpha
Curiously, the “relay” mentioned in ARRL, is a form of a DTN. They were doing
this a hundred years ago, just manually!

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macintux
Tried to comment on the page before it died. There's at least one vaguely
plausible chain of events that could lead to DTN being ubiquitous: if/as
vehicles start communicating with each other as we approach full autonomy,
incorporating DTN into those communications would seem a possibility.

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kb1lqc
Woops, try again. Network issues this morning with the website.

(I am one of the co-founders of FaradayRF ;)

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tlrobinson
I wonder if there's opportunity for collaboration with Secure Scuttlebutt,
which is essentially a DTN:
[https://www.scuttlebutt.nz/](https://www.scuttlebutt.nz/)

