
LoRaWAN packet received at record distance of 702 km - htdvisser
https://www.thethingsnetwork.org/article/ground-breaking-world-record-lorawan-packet-received-at-702-km-436-miles-distance
======
owenversteeg
So, this raises a question I've been meaning to ask for a while. Let's say you
want to transmit a very small amount of information over a very long distance
(say 80 bytes over a minimum distance of hundreds to thousands of kilometers.)
What options are there that are relatively small-sized?

Let's say maximum receiver size is roughly 10cm by 10cm, and power consumption
can't be over 10 watts, but the "base station" can be as large and powerful as
you want.

[edit] cause this is getting some upvotes, here's some thinking I was doing:
you can't go through the ground (unless you're at ultra low frequencies and
those need antennas measured in tens of kilometers long). So you pretty much
have to bounce stuff off the atmosphere, right? When you see stuff like this
[0], with thousands of kilometers of range, I imagine that's what happening.
Especially as that's 10MHz, which is 30 meters wavelength, which bounces off
the atmosphere pretty well IIRC. The only thing with that is that the powers
are incredibly low and the antennas are huge. What if you increased the power
but decreased the antenna size, for example a 10cm x 10cm antenna with 10W?
100W? 1kW? Would transmissions across thousands of kilometers still be
possible?

~~~
PoachedSausage
What you are describing there is basically longwave AM radio broadcasting.
Large transmitter, small transistor radio receiver.

Low speed data can be and is sent using such transmitters, it is done by phase
modulating the carrier. The data can be used to switch electrical appliances
on and off.

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

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

Droitwich puts out 500kW and reception range is on the order of 1000km.

~~~
owenversteeg
Right, but that's only one direction. I thought I put it in my comment, but
I'm only curious about bidirectional stuff. The best path forward here seems
to be WSPR- like stuff, but that requires larger transmitters on the order of
tens of meters.

~~~
PoachedSausage
That's the problem, an asymmetry in transceiver size does not really lend
itself to bidirectional unless its relatively short distances like cellular
phone networks.

------
Animats
Wow. Both the receiving and transmitting antennas were omnidirectional.
There's no problem doing this with a dish pointed at a dish, but that low
power without directional antennas is impressive.

~~~
sbierwagen
Ho ho, is nothing! Try 7,869km, transmitting at 10 milliwatts. The
transmitter? A couple passives attached to a GPIO pin on a raspberry pi:
[https://gerolfziegenhain.wordpress.com/2013/04/13/raspi-
as-w...](https://gerolfziegenhain.wordpress.com/2013/04/13/raspi-as-wspr-
transmitter/)

The catch is, thanks to Shannon of course, bandwidth. WSPR will do something
like 1.46 baud. That and the 13 meter long antenna.

~~~
revelation
Try hundreds of meters deep in seawater, all around the earth:

[https://en.wikipedia.org/wiki/Communication_with_submarines#...](https://en.wikipedia.org/wiki/Communication_with_submarines#Extremely_low_frequency)

Bandwidth is even worse though (<<1 baud), and don't start on antenna length.

~~~
Cyph0n
How about while drilling 1000s of meters underground? How do you transmit data
back to the surface? This is a problem faced by oil drilling and exploration
companies, and they have a solution for it. Take a guess what it is...

Mud modulation.

Basically, while drilling, mud is pumped down the drill string and back out
for cooling and cleaning purposes.

Some genius at one of the major oil drilling companies (maybe Schlumberger?)
came up with the crazy idea of modulating the mud pressure to transmit
information into the depths of the earth. You can control the drill bit speed,
angle of drilling, and monitor all sorts of diagnostics over a mud-based
communication channel. The bandwidth is decent (think: dial-up), especially
when the drilling tools use an efficient modulation scheme.

It's amazing stuff to see first-hand.

~~~
orf
That's... both crazy and ingenious in one package. I love it.

~~~
trhway
>both crazy and ingenious in one package.

wait until you see the NSA mud-pipe-tap.

------
vvanders
Good stuff, HAAT(height above average terrain) always makes a big difference.

I regularly see APRS packets of 120mi+, although probably at a lot more power.
The current record seems to be near ~2,000 mile[1] bounced from the ISS.

[1] - [http://qrznow.com/new-iss-packet-distance-record-
claimed/](http://qrznow.com/new-iss-packet-distance-record-claimed/)

~~~
egeekuk
Might just be me, but I read this as ~2 kilometers, rather than the intended
~2,000 miles.

~~~
vvanders
Haha good catch fixed that, meant 2,000 miles.

------
api
On the higher speed front: has anyone looked into 802.11ah (900mhz wifi) or
any of the smart "TV white space" stuff? It's standardized but I can't find
any hardware on the market. There is a company near us (Irvine, CA) that
apparently has an 802.11ah chipset but no cards or USB versions and emails go
strangely unanswered. Found them since they had a press release about hitting
like a few tens of megabits at over a kilometer on very low power and a small
omnidirectional antenna.

~~~
jlgaddis
Motorola (Canopy) used to make a bunch of 900 MHz (ISM) radios that were
popular with WISPs. They weren't technically Wi-Fi but a proprietary protocol.

I can't recall if Ubiquiti ever had any 900 MHz radios or not but they have
plenty in the 2.4/5 GHz (unlicensed) bands as well as the 3.65 GHz (licensed)
bands that would probably serve your needs for cheap. Unfortunately, the 900
MHz band is getting quite crowded these days, leading to lots of interference
and reduced "throughput".

Mimosa is another (younger) company making similar gear that's relatively
cheap with good bang for the buck.

A place I do some work for has several 15-20 mile links (6/11 GHz) pushing
~500 Mbps although those are much more expensive.

------
aw3c2
From a balloon in almost 40km altitude. Still impressive but nowhere as
impressive as I read this headline. I thought this was ground to ground...

~~~
vvanders
Ground-to-ground is limited by the curvature of the earth(unless you're
bouncing things off the atmosphere like with HF radio). Generally even with a
repeater on a mountain nearby the best you can expect is ~100mi.

~~~
jws
There are many spots on the Earth with longer LoS views. Here is an
interesting list along with photographs people have made of them:
[https://beyondhorizons.eu/lines-of-sight/](https://beyondhorizons.eu/lines-
of-sight/)

The longest one with a photograph is 443km (275mi).

~~~
DanWaterworth
Comments like this are why I still read hacker news.

~~~
mhh__
IIRC the above link was the frontpage not that long ago. Very interesting

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kbumsik
That’s great. I am wondering what was the throughput at that distance...

~~~
dfox
It's LoRa, so probably 50-ish byte packet transmitted at 800-ish bits per
second.

~~~
ju-st
How many channels does LoRa have?

~~~
dfox
It is variable-bandwith spread spectrum modulation, so talking about discrete
channels does not make that much sense. But each of frequency bands it
operates in is notionally divided into 9-11 uplink and downlink channels.

The modulation scheme is essentially FM with a twist: high bitrate mode is
essentially straight FSK and lower rate modes are FM modulated with sawtooth,
which is or is not inverted in each period depending on the transmitted bit.
The idea is essentially same as various QRP modes involving painting images on
waterfall diagram. (Full gateway nodes receive full band and can track ~50
transmitting nodes at once)

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qwerty_asdf
This is the most "out there" thread, involving emerging technology, that I've
seen on HN in a while.

