
NPR: New Packet Radio - wglb
https://hackaday.io/project/164092-npr-new-packet-radio
======
gonzoflip
This is a very cool project!

I would be concerned about unintentionally running afoul of FCC regulations
since encryption is not allowed on US amateur frequencies, that means using
something like SSH or loading an SSL webpage with this modem would be a
violation. I would also be very concerned with the OS background processes
that may use encryption by default.

~~~
edoo
They don't allow any prototyping or experimenting on the amateur bands either.
That is why this is using the unlicensed ISM bands.

I want to see it adapted for the lower frequency ISM bands. I just got into
ham and SDR this last year and I'm looking forward to making a super long
distance super low speed link to my buddies on the other coast as a backup
comm channel in case the primaries go down.

~~~
mises
> super long distance super low speed link

Interesting, can you provide any more information? How could you do radio that
far? Googling shows it is at least 2,092 miles. What kind of radio can go that
far?

~~~
sciurus
The HF bands (below 3 and 30 Mhz, also called shortwave) propagate by bouncing
of the ionosphere. A major part of amateur radio is using them for
intercontinental communication.

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

~~~
sciurus
That should have said between, not below.

Also, I'll add a link to
[http://wsprnet.org/drupal/wsprnet/map](http://wsprnet.org/drupal/wsprnet/map)
. Essentially this shows the transmitter and receiver locations for low power
beacons, which might give you a sense of what HF propogation looks like. It
will vary according to the time of day and solar conditions.

------
bloomer
Useful description from the documentation about what is new about this as
amateur packet radio has a long history.

The NPR protocol is designed to transfer IP data over radio links, in a
bidirectional way (single frequency). This protocol is in the middle between
old packet radio (AX.25) and HSMM-Hamnet with Wifi equipment. This protocol is
designed by a HAM for HAMs. The project is 100% open source : specification,
software, PCB.

This solution is complementary to HSMM-Hamnet (which uses Wifi equipments), on
lower frequencies 70cm). Radio links on 70cm band is much more robust to
obstacles. The data-rate available is also much smaller, but yet useable. We
can achieve several hundreds of kbps. The protocol is designed for “point to
multipoint” topology, with 1 central relay (called Master) and several clients
around.

------
nickysielicki
I wonder if IP is really the right decision. AX25 isn't the bottleneck with
existing packet radio, and because it's made for hams, it makes it easy to be
sure that you're really within your license requirements. ie: identification.
It's also difficult to accidentally send encrypted messages over AX25, whereas
on IP you have to really watch Wireshark and make sure you're not doing
something wrong. It's also not as chatty, which is a real concern when you
have a mesh network and someone is hearing you better than you're hearing them
--- it could get really messy without coordination. That being said, this is a
very exciting project. I'd love to see packet radio make some progress since
the 80s (outside of just repurposing 802.11 gear).

We need the ARRL to stop wasting their time on a watered down HOA bill that
they've been working on for like a decade, and start talking to the FCC about
modernizing regulations for the 21st century. Two things that come to mind are
that the spread spectrum/transmit bandwith restrictions are outdated, and
encryption requirements need to be formally relaxed so that common digital
communication like SSH or HTTPS can be supported to an extent -- I'm not
saying I want the ham bands filled with encrypted traffic, but I'm fine with
the small community of packet radio enthusiasts being able to remote into a
computer from afar.

~~~
robocat
> start talking to the FCC about modernizing regulations for the 21st century

I would have thought that HAM operators need to fight to keep the regulations
that they have, and that trying to make big changes would lead to worse
outcomes?

~~~
bloomer
Any of the regulations predate most digital communications so there are a
bunch of obsolete rules specifying the maximum symbol rate for digital
transmissions rather then restricting the bandwidth which is what one actual
cares about for sharing the available frequency space. This restriction
artificially precludes use of many modern transmission schemes and hamstrings
experimentation.

------
theWheez
This is very cool!

I had an idea for something like this a few years back, would love to
experiment!

Any idea where this falls in terms of broadcast regulations? From what I can
recall in the US, data must be in the clear and not encrypted on ham
frequencies, although I am not a licensed ham so can't say for sure.

Love this!

~~~
wglb
You are correct.

Additionally, no commerce is allowed, so connecting this to the actual
internet would be fraught with risk.

~~~
goda90
So encryption isn't allowed, but is there any way to authenticate information
sent over packet radio? Open communication has plenty of uses, but some of
those can be spoiled by bad actors impersonating others.

Edit: I found this article on authentication that supposedly is fine, but I'm
not licensed so I don't know how valid it is.
[https://rietta.com/blog/2009/08/17/authentication-without-
en...](https://rietta.com/blog/2009/08/17/authentication-without-encryption-
for/)

~~~
nominatronic
There's no problem in principle with using public key cryptography to sign
messages sent by ham radio. So authentication is possible although it's not
common in practice. It's encrypting the content of messages that's not
permitted.

~~~
kawfey
Legally speaking, it's "messages encoded for the purpose of obscuring their
meaning" [0] that's illegal, which is fraught with conflicting interpretations
and loopholes.

[0] [https://www.ecfr.gov/cgi-bin/text-
idx?SID=f9e42063714bbba9b7...](https://www.ecfr.gov/cgi-bin/text-
idx?SID=f9e42063714bbba9b7bb83ef26e844ca&mc=true&node=pt47.5.97&rgn=div5#se47.5.97_1113)

------
chooseaname
In my utopia, everyone would have access to something like this and the
internet would be free from the chains of corporate greed.

There's a lot to overcome (having everything be completely decentralized), but
a person can dream...

~~~
reaperducer
50 years ago the notion of everyone having their own computer (or several!)
would have been laughable.

Perhaps in the next 50 years people will have their own personal satellites in
orbit and we will achieve your goal.

~~~
penagwin
Getting a satellite into space is ~50,000$ for a 1U cube sat when I looked
around. You _might_ be able to get NASA or somebody to send it up for free if
it's educational and they have room.

So it's getting cheaper for sure! While that's certainly not the cheapest,
it's now within reach of small startups/passionate makers which is exciting!

~~~
monocasa
More likely in 50-100 years is manufacturing capacity in space gets to the
point that building a 1u satellite up there is way cheaper than sending from a
deep gravity well like Earth's. I imagine at some point, rockets will only be
used for sending people and other things that can't be transmitted or
manufacturered.

~~~
jonfw
Still going to pay transport costs on getting raw materials to space, although
I imagine raw mats will be densers and the volume savings will reduce costs.

~~~
monocasa
There's plenty of raw materials in space via asteroid mining, particularly
everything you need for satellites.

~~~
penagwin
But on currently on earth we have many massive factories to collect, refine,
and process just the raw materials. Those factories will require massive
amounts of resources to boot, and we don't start with any resources in
space....

~~~
monocasa
Right, so it's a bootstrapping question. If this was your long term goal,
you'd right now be working on reusable rockets that you'd soon be using at
cost to send up large quantities of infrastructure (cough cough Blue Origin
and Space X, Space X being further along and openly talking about Starlink).
Next step is mining asteroids for stuff like platinum and dropping it down to
earth. Step after that is manufacturing with those raw materials in micro G.
Now you have a complete manufacturing chain without gravity wells, and
ostensibly a multi trillion dollar company.

~~~
ngold
This is the exciting future of space.

I love that comment sections are inevitably choked up with people say can't or
won't since it's easy to say no.

------
rsync
Forgive my ignorance ...

What is the range of HSMM/Hamnet ?

Can you have a "Hamnet BBS" and if so, do you need a separate radio for each
"line" ? Or can the BBS have a single radio that shares incoming connections
on different sub-frequencies of (whatever band you're using) ?

~~~
jrockway
This is on the 70cm band so basically line of sight. The curvature of the
Earth is the limiting factor (but you can always bounce it off something
reflective in the sky; see meteor scatter, airplane scatter, moonbounce, etc.)

------
henrikeh
I’m so happy to see something like this! Communication engineering is a field
which impacts everyday life all over the world and more people should have a
chance to learn about it. Open hardware and software is an excellent resource.

------
kerouanton
Nice project, but why are all hardware guys designing projects without ANY
security?

Page 14, the guide explains the connection to the modem is possible with
Telnet with no password...

That's a common issue in IoT and embedded systems, it seems, so I'm wondering
if there is a reason why hardware developers just fail at security ?

~~~
microcolonel
This protocol is designed for HAM, and for the most part you can not make
encrypted transmissions over amateur radio.

~~~
kerouanton
Maybe (I'm also a HAM licensee) but making a device available on a IP network
without any authentication and weak protocols such as telnet doesn't justify
this.

~~~
microcolonel
I don't think there would be any issue with signing your datagrams, you just
can't obscure the content of the communication or its purpose.

So yea on authenticity and access control, nay on transmitting ciphertext.

------
philpem
I love the concept - I've been working on something similar myself using an
MMDVM (with custom programming) and a pair of Icom mobile transceivers.

My only comments from reading the protocol spec -- and I need to emphasize,
this is one British ham's opinion and is worth precisely what you paid for it,
i.e. nowt :)

\- Data whitening is a great addition. Too few ham protocols use this, and as
a result it's a pain to find suitable transceivers (other than ham-spec ones)
for them on the used market.

\- Forward error correction scheme looks a bit weak. Nice compared to most ham
protocols though (which sometimes just have a CRC). The main thing is, if you
get a burst error which straddles two blocks, you lose block N's CRC and block
N+1's first few data bytes -- which would be uncorrectable.

\- It'd be nice to see some narrowband modes, maybe 8Kbps in a 12k5 narrow
channel or 16Kbps in a 25kHz channel. With 45kHz deviation 360kbps 4GMSK (Mode
22), you're looking at 270kHz bandwidth. That's pretty darn wide! So wide, in
fact, it wouldn't be reasonably usable in the UK if you wanted to adhere to
the RSGB Bandplan.

I think it should be possible to get some pretty big improvements in error
correction by using a better error-correction code (POCSAG's (31,21)BCH code
would be a good starting point) and employing bitwise interleaving.

The idea is -- you'd add the error correction first, then interleave the bits.
This means that when you deinterleave things at the other end, any burst
errors will become single-bit errors in multiple codewords. Single-bit errors
are much easier to fix than bursts!

8:1 interleaving with POCSAG's error-correction scheme would give a 21-byte
packet size inside a 32-byte transmitted block (giving ~67% efficiency or ~33%
overhead). It'd be able to correct up to a 16-bit error burst thanks to
(31,21)BCH's ability to correct 2 erroneous bits. This is, actually the same
method used by the FLEX-TD paging protocol (documented in ARIB standard RCR
STD-43) :)

73's, de M0OFX :)

EDIT: Forgot to show my working, oops! The GFSK occupied bandwidth formula I
used was from here:
[https://www.silabs.com/community/wireless/proprietary/knowle...](https://www.silabs.com/community/wireless/proprietary/knowledge-
base.entry.html/2015/02/17/calculation_of_theo-S9wI) (bear in mind GMSK is
GFSK with the requirement that the modulation be phase-synchronous, i.e. data
changes only occur when the IF/RF is at zero phase)

I just calculated the OBW of Mode 24 (4GMSK 500ksym/sec). 750kHz! That'd be 30
of the 25kHz Digital Comms channels... yikes. I'd expect complaints from local
hams about the QRM.

------
zamadatix
I think IP is a better fit for the 900mhz range though I'm no expert in the
radio space. It's a shame 802.11ah never took off in hardware.

~~~
int_19h
You get higher bitrates at higher frequencies, but you also get more
attenuation and hence shorter distances.

------
johnklos
Ummm... Could you pick a name that isn't already taken by something we all
already know?

------
tyingq
Very cool. Might consider that having the terms "NPR" and "Radio" in the same
phrase will confuse some people. Most will think of
[https://www.npr.org/](https://www.npr.org/)

~~~
joncp
I bet they'll be hearing from NPR's lawyers

~~~
24gttghh
Just call it GNPR?

