
Openwifi: Linux mac80211 compatible full-stack 802.11/Wi-Fi design based on SDR - homarp
https://github.com/open-sdr/openwifi
======
newhouseb
This relies on OpenOFDM for much of the "Physical" layer of WiFi, which has
some INCREDIBLE documentation that is really worth checking out if you want to
understand how modern radios go from a radio signal to packets:

[https://openofdm.readthedocs.io/en/latest/](https://openofdm.readthedocs.io/en/latest/)

(Modern) WiFi shares a lot of similarities to the physical layers of LTE/5G NR
in their more basic modes, so this is useful well beyond WiFi.

~~~
non-entity
Wow. I once wondered about building a wifi card with an SDR but quickly got
discouraged when figuring out how much IEEE charges for the specifications.

~~~
sohkamyung
Most of the IEEE 802 specs (including the base IEEE802.11 WiFi spec) are free
[1]. But you do need to at least register to get access to them.

>New IEEE 802® standards are included in the program after they have been
published in PDF for six months. All standards available in the IEEE GET 802™
program will remain in the program until they are replaced by a superseding
document or are withdrawn. Drafts are not part of the program.

>

>To download these standards, you must sign in with an IEEE Account. If you do
not already have an IEEE Account

[1] [https://ieeexplore.ieee.org/browse/standards/get-
program/pag...](https://ieeexplore.ieee.org/browse/standards/get-
program/page/series?id=68)

~~~
non-entity
I read about this program on several sites including the Linux wireless
project page and the osdev wiki and the links seemed broken everywhere. Not
sure why I didn't find this before.

~~~
sohkamyung
I believe the Get IEEE project has shifted its web location over the years,
which probably explains those broken links.

I did a search for "Get IEEE" which gave me the updated one.

------
jhallenworld
This project (and OpenOFDM) is massively impressive. The standard is complex,
and almost nothing works until just about everything is working. They should
write a blog about when the first ping worked.

Anyway, there is a lot of value as a testbench or as a standard implementation
for others. I can only imagine how much a testbench would cost...

[https://ip.cadence.com/uploads/706/dsv-sim-eth-
wireless80211...](https://ip.cadence.com/uploads/706/dsv-sim-eth-
wireless80211-pdf)

~~~
jxj
I like this sentence "nothing works until just about everything is working".

Actually the first ping worked in the end of 2018 to the beginning of 2019.
But like you also realize, it is complicated, and actually well beyond my
original imagination. So between the first ping and the release status (at the
end of 2019), there was a lot of work. Finally it comes to today, and it runs
"normally": stable ping, stable throughput, less crash. Huge effort is needed
just to make things work as normal.

------
etaioinshrdlu
It seems one of the final missing links to fully open source hardware WiFi
would be the RF transceiver chip. This is, to my understanding, something
similar to a high-bandwidth DAC and ADC coupled with configurable frequency
mixers to access radio frequencies.

Is anyone trying to create an open source version of that chip? I understand
there's not a lot in the way of open source analog chip designs out there, but
with Google/Skywater's free PDK, the time may be ripe to change that.

Also, there are many SDR LTE base stations, but can we make our own SDR LTE
handset as well? Can it connect to an existing cell network?

~~~
myself248
How open does it need to be?

If you're willing to take up a suitcase worth of room, you can use standard
analog ICs and RF building blocks to take a quite normal DAC and upconvert it
to RF, and downconvert the receive chain likewise to a very common ADC. The
standard wifi channel width of 20MHz should place it within reach of quite a
few off-the-shelf chips.

That approach should be able to do the whole thing with no NDAs or whatever;
it would be a fine capstone project for someone chasing an EE/RF degree...

~~~
exikyut
The HackRF One can do 1MHz-6GHz, but also indicates "8-Bit I and 8-Bit Q".

On the one hand I'm like, it's basically just dumping wideband spectrum into
the air, right?

On the other hand the OpenOFDM reference talks quite a bit about much larger
I/Q values, so maybe "8-bit quadrature samples" is exactly why nobody uses it
for Wi-Fi. :(

(Yup, am RF noob)

~~~
fake-name
The HackRF One uses a series of up/down converters, plus a MAX2837 for tuning,
and a MAX5864 for the actual ADC/DAC. It goes 22 MSPS, so it can theoretically
look at any ~20 mhz section of the 1 MHz - 6 GHz tuning range.

WiFi channels are generally 20, 40 or 80 MHz, so the latter two are not
possible given the hardware, and the smallest (20 MHz) would be right at the
limit of the hardware. Additionally, there may be other complications (tx/rx
switching speed, tuning speed (I'm not sure if wifi would need to do frequency
hopping, and if the bandwidth is sufficient to mitigate that need), etc...)

And then someone would have to actually implement it.

~~~
non-entity
Sadly from my research of cheap and hobbyist SDRs, you generally aren't gonna
get high bandwidth. I have a limesdr-usb sitting around which supports ~60mhz
bandwidth iirc which wasn't good enough for a specific application I looked at
which required a channel width _up-to_ 192mhz. Although I'm also an absolute
RF noob, do I may have misinterpreted something.

------
bb88
Question: How does the AGPLv3 work when it's describing/programming hardware?
I have a good idea how it works on software, but less than a good idea on
hardware.

------
homarp
see also
[https://www.youtube.com/watch?v=Notn9X482LI](https://www.youtube.com/watch?v=Notn9X482LI)
a talk introducing OpenWifi

~~~
tambourine_man
0.2 ms latency.

Pretty good.

~~~
mikenew
That's about what I get with my desktop using Cat6 -> Network Switch -> Cat6
-> router. That's very impressive.

------
antsoul
His talk at Fosdem :
[https://fosdem.org/2020/schedule/event/fsr_openwifi/](https://fosdem.org/2020/schedule/event/fsr_openwifi/)

------
Serious_Cheese
Please excuse my ignorance,I'm fairly new to this field. So with OpenWifi,
will I have control as to what packets I would like to send over the air? So
for example, can I construct a specific packet using OpenWifi and then send
them over the air over a specific channel (say channel 11, 2.4 Ghz)?

~~~
alex7o
Not exactly, you can already do this using monitoring mode on your normal WiFi
card. This is using SDR(software defined radio) to create a WiFi card from
scratch. Technical speaking you can recreate any radio signal using SDR, with
some limitations of course.

------
djsumdog
How does licensing work with software defined Wi-Fi? As I understand it,
Australia holds many Wi-Fi patents and most of the money from radios goes into
their University system. Would SDR based implementations be in violation of
those patents? What if someone made a hardware version?

~~~
shakna
Some of those patents have expired, so it would take a lot of research to be
certain. A hardware implementation is likely to be patent-infringing.

The SDR implementation is unlikely to be patent-infringing, as Australia does
not generally allow software patents. [0] Software implementations of existing
hardware are generally not considered to be patent-infringing under the
current interpretations of law.

However! The SDR implementation is still likely to be copyright-infringing, as
Australia does have copyright laws that are rather vague and far reaching, and
Australians are not granted the right to give up copyright.

[0] Software patents can be granted, but they require the idea "improve the
computer" rather than "merely requires generic computer implementation". Which
is a higher hurdle than people expect, and has led to IBM, Microsoft and
others losing and failing to gain software patents in Australia.

~~~
wmf
OpenOFDM looks like Verilog running on an FPGA; is that "software"?

~~~
shakna
So far as I'm aware, that question has yet to be tested in an Australian
court.

As Australia operates under rules that translate to "reasonable
interpretation", rather than strict definitions, the answer to your question
is "Maybe".

------
linuxlizard
Is the paper available elsewhere?
[https://biblio.ugent.be/publication/8663043/file/8663044.pdf](https://biblio.ugent.be/publication/8663043/file/8663044.pdf)

~~~
homarp
try [https://www.orca-project.eu/wp-
content/uploads/sites/4/2020/...](https://www.orca-project.eu/wp-
content/uploads/sites/4/2020/03/openwifi-vtc-antwerp-PID1249076.pdf)

~~~
linuxlizard
Works. Thank you!

------
cjbprime
Extremely surprised to see AGPLv3 used instead of GPLv3, given that this looks
like binaries that you install on a device rather than a network service you
connect to. Anyone know what's up with that?

~~~
wmf
In dual licensing you wan the free option to be as scary as possible.

~~~
epse
The dual licensing is not used at all and getting shit open sourced out of my
uni is a royal pain. Source: doing my masters with openwifi at this research
group

------
jl2718
Somebody shoot holes in my idea. I want to do wifi over coax with the baseband
into the coax and the up/down converter on the antenna side. This is
interesting for such a project, but of course I want full speed modulation
(gigabit). I don’t want to just transmit data like MoCa. I want a direct
interface to an antenna. The point is to make roaming over large distances
completely transparent to the client.

~~~
zbrozek
Downsides:

\- Very nonstandard

\- Limited client density (could be fine in a house)

\- Beam-forming probably out of the question

It would probably work OK though. But why is it better than making 802.11r
work? From my perspective as a user (not as a client node) it's completely
transparent.

------
person_of_color
So what's the max tput?

~~~
jxj
Hello,

This is the author Xianjun.

When communicate with commercial device, tcp can achieve ~30M, UDP can achieve
~38M in 20MHz 11a/g non MIMO mode. We are still working hard to optimize the
whole design, because we know it is not mature enough and there is still lots
of work to be done. For example, the original PHY rx openofdm design is
simplified a lot for a quite small fpga which means performance (like
sensitive) is sacrificed. Now our FPGA is more advanced than the openofdm FPGA
in USRP N210, so there is a chance to improve a lot on both performance and
features (like MIMO and new standard). Recently nlnet.nl gives us a short term
fund to complete the 802.11n feature:
[https://nlnet.nl/project/OpenWifi-80211n/index.html](https://nlnet.nl/project/OpenWifi-80211n/index.html)

There are lots of information (including throughout) in the readme and
“project document” on GitHub ([https://github.com/open-
SDR/openwifi](https://github.com/open-SDR/openwifi)). Worth to read word by
word.

------
knorker
AGPL? Nope nope nope.

It's a shame. Sounded like it would have been interesting.

~~~
jxj
How so?

~~~
knorker
AGPL is very controversial. I'm clearly on the "won't touch it with a 10 meter
pole" side.

There are people with other opinions, but even they agree that this is not
tested in court, and it's more expensive to be sued, even if you win, than to
just buy (or write from scratch) ANY alternative to the AGPL software in
question.

AGPL is a legal landmine. You can't plug it into anything else, even for your
own purposes.

Let's say you use these to create a guest wifi network. According to AGPL it
looks like you must now opensource any and all scripts that you use to manage
this environment.

In other words that one-off script you used to loop over all your access
points during setup must be opensourced. Oh, it has details about your
internal asset tracking system? Well, they now have to be public. Oh, it
_relies_ on your internal database? I guess that's opensource now too.

Did you even keep that one-off script? AGPL demands that others must be able
to run what you run, essentially. It says that everything you do
_operationally_ to your service must now be documented and published.

You want to connect your internal SSO to the AP? Sorry, you better instead
change it so that your internal SSO takes whatever protocol the AGPL software
already takes. Oh, that's not feasible? Ok, give up then.

1 year later… oh shit oh shit oh shit, someone added internal SSO to the AGPL
software! Now we have to opensource that, but we can't because it includes
code we licensed from a third party only for nondistribution!

AGPL only makes sense for organizations that fundamentally ONLY will EVER run
open source software (like FSF and that's it), and usually not even then.

Also ideologically it's a huge violation of freedom. What I do in my own home
is absolutely none of your business. What executes on my hardware is my
business.

For those who disagree about my examples: Yeah… I'm personally not a lawyer
(but HAVE consulted with lawyers about this). You may be right. In the end a
court will decide. But do you want to take this poison pill in order to find
out in court if you die?

~~~
jxj
So GPL doesn’t have this character? Like the GPLv2 taken by Linux kernel. I
have an impression that AGPL only add “A” to GPL to adapt itself to the cloud
era. Because a cloud/service deployment is not treated as redistribution in
GPL, considering there wasn’t cloud at the time GPL was made. So some big
cloud company can deploy GPL software on cloud without open source action
because they are not actually “distribute” software, instead only distribute a
service. AGPL fix only this hole created by cloud.

~~~
knorker
Correct, GPL doesn't have this character.

You say it "fixes" GPL, but as I described it makes AGPL completely unusable
for basically any purpose, and it creates a HUGE risk that's in my opinion
completely unacceptable, as described.

The only way it seems to work is: 1) it's extremely unpopular by number of
projects 2) most private citizens who use it violate the license 3) most
potential corporate users have it vetoed by their legal department, which
means they plain don't use it

That's not a great situation. It only seems to work (in the rare cases that
it's used) because so few people accept it, and the ones that do violate it.

AGPL removes freedom zero, in my opinion.

> The freedom to run the program as you wish, for any purpose (freedom 0).

I think my examples illustrate this, but I'm sure I could elaborate more.

The way I read it you cannot write an automation script for managing the
MongoDB databases for your Etsy store without opensourcing those scripts.

In fact I disagree that "cloud didn't exist when GPL was created". This also
applies to services like banks, and banks certainly existed before GPL, and
provided a service.

So that was never a "hole" in GPL.

AGPL is poison because every time you touch it, even operationally, your work
belongs to someone else. To call that "Freedom" is Orwellian.

~~~
jxj
But in the MongoDB case (when it was still using AGPLv3), those companies who
violated AGPLv3 did have a solution: pay a fee for a commercial license of
MongoDB instead of AGPLv3 which is free. In this way, those companies don't
need to open source their code built based on MongoDB. MongoDB get money to go
further, because I guess MongoDB people need to raise their family.

~~~
knorker
Sure. But if anyone who seriously uses some software (even on a hobby project)
is either violating the license or buying a commercial license, in what sense
is it free/libre software or even open source?

That's saying that AGPL is only useful to the extent that it doesn't exist.

But it's not just software "based on" MongoDB. It's your backup scripts. It's
your cluster scheduling config for the jobs. It's your provisioning script,
etc…

And it implies it being non-free software. It's only one (small) step removed
from a licenes that disallows "commercial use".

A license disallowing commercial use is fine. But it's absolutely not "free
software". Freedom zero was so obviously a freedom that it was initially just
implied, and only added later to be explicit.

~~~
jxj
If you are saying AGPL's virus like behavior is much more severe than the
GPL's virus like behavior, I am not professional on this aspect. Not sure.

If I understand correctly, the open source action is only required when you
"re-distribute" it. So, if you play it only by yourself and never give your
modified software to anyone else, it is OK for you to keep all code close. If
you work on it together with other people in your organization, it is fair
enough that you open the source code to those people for them to work together
easily. But all the code are still kept inside your organization.

Only in a step that you want to re-distribute the software (or the service) to
people (like external user or other company) who you don't want to show source
code, you are facing violating the AGPLv3. But generally speaking, in this
step you already have a plan to make money out of external people (like user
or other company), so fair enough to pay a fee for commercial license.

"free software" or freedom zero is good, but how engineers/companies who
develop free software make survival? Donations? If I am already a billionaire,
I totally support your point.

~~~
knorker
> If you are saying AGPL's virus like behavior is much more severe than the
> GPL's virus like behavior

Well, it is, since it extends GPLs coverage to not just "linking" (a hard to
define term) but also explicitly even to automation scripts.

But I'm also saying it's not just a difference in degree, but in _kind_.

> If I understand correctly, the open source action is only required when you
> "re-distribute" it. So, if you play it only by yourself and never give your
> modified software to anyone else, it is OK for you to keep all code close.

For GPL this is true. For AGPL it appears to apply to any artefacts or other
public interactions too.

> Only in a step that you want to re-distribute the software (or the service)
> to people (like external user or other company) who you don't want to show
> source code, you are facing violating the AGPLv3.

Maybe. It's untested in courts. A very reasonable interpretation (that I
subscribe to) if your BooksOnlineExample.com uses AGPL for backend storage,
then that is covered by AGPL (but not GPL).

But even worse. If you use some AGPL software to compress some data as you
transfer it to your backup tapes, then you are using this AGPL software in
order to run BooksOnlineExample.com (after all, without backups you don't
really have a service), and thus your backup script could very well be in
scope for AGPL and may have to be published.

Google has some opinions on this, e.g. this:
[https://www.theregister.com/2011/03/31/google_on_open_source...](https://www.theregister.com/2011/03/31/google_on_open_source_licenses/)

> But generally speaking, in this step you already have a plan to make money
> out of external people (like user or other company), so fair enough to pay a
> fee for commercial license.

Ah, but AGPL is not about covering the "making money hole". It's about the
"cloud hole". I would argue that GPL never had any intention of preventing
people from making money.

Do you think Linus is upset that maybe tens of thousands of companies have
their own patches to Linux to run their service? Do you think he's upset that
even the ones that _don 't_ patch the kernel don't publish their kernel
config. (I don't know if you've ever built the kernel, like "make menuconfig",
but this is definitely not just "settings", but actually a vital step in order
to "reproduce the same binaries as run on your production servers")

GPL was extreme when it was created. Compare it to the BSD license. Then AGPL
came along and just went absolutely off the wall by having your _interactions_
with the software bind you to publish.

> "free software" or freedom zero is good, but how engineers/companies who
> develop free software make survival?

To be clear, are you saying that the main goal of AGPL is to have people NOT
use it? Because people who do accept and abide by the terms of the AGPL
license do NOT pay for it.

AGPL only prevents use. You're assuming all AGPL software is dual-licensed,
which is very much not the case. Luckily very little software is AGPL.

If it's about money, then why use AGPL at all? Why not just have a commercial
license? Because you're not giving anyone even the most basic freedom with
AGPL.

If the goal of choosing AGPL is to get paid or not use it, then that's just
commercial software. Which is fine, but don't call it free software, since
it's anything but.

~~~
jxj
Ok. Actually I never (and don’t know who) call AGPL software a free software.
Let’s just call it AGPL software! Problem solved.

Just curious, if AGPL is so evil, who made it for what kind of purpose from
the beginning? You give me an impression that AGPL is totally wrong and
shouldn’t be born.

I am not saying that AGPL is born to prevent people to use AGPL software.
Instead, AGPL definitely encourages people to use for free under the license,
or use it after purchase commercial license. Why you have impression that AGPL
was born to let people not use the software?

Like MongoDB, it selected AGPL from the beginning, and many people were using
it (so you can’t say AGPL stop people to use MongoDB), until some big
commercial companies began to deploy it in cloud and violate AGPL (refuse to
open source). This hurt the protocol and MongoDB, so MongoDB decided to change
the license to a more explicit and strict license written by themselves to
rule explicitly that if you deploy the MongoDB in cloud you should be open
source. Otherwise you need to purchase a commercial license. From this point
of view AGPL or the more strict MongoDB protocol find a good balance between
open source and commercial usage. Please tell me if MongoDB uses more free
software style license, like GPL, Apache, MIT, I guess many companies will use
it in non open source style without violating the protocol, then how MongoDB
can survive? If MongoDB can not live a good life, who will contribute to it,
maintain it, help user continuously? MongoDB dies and the world gets nothing.
Happy ending?

I am glad that google doesn’t like AGPL. To me this implies that the thing,
that is not liked by big company, could be interesting. Google has become a
gigantic monster. AGPL just prevents the big companies , like google, amazon,
to use open source software for free.

~~~
knorker
> if AGPL is so evil, who made it for what kind of purpose from the beginning?
> You give me an impression that AGPL is totally wrong and shouldn’t be born.

Then I have succeeded in conveying my opinion. :-)

I think it was made with good intentions, but without thinking through the
repercussions. It's made for a world where everything is opensource, and
everyone has incentives to keep it that way.

But it's a fantasy world that doesn't exist. If all open source OSs were AGPL,
then that would not force Google to start publishing their internal drivers.
It would force Google to write their own Unix-like OS. It's a lot of work,
yes, but especially if it's only for your own purposes it's not _that_ hard.
And they've done it before.

> Why you have impression that AGPL was born to let people not use the
> software?

Like I said any serious (I don't mean commercial) use of software requires
automation and other surrounding stuff to make it work in a given environment.
Yes, you can run MongoDB for fun at home, but considering that I've written
scripts for my Ubiquity access points to collect some data, I'm glad that
their software isn't AGPL. Even in my home use I would be forced to publish
those scripts. Because it's not just me the legal entity that uses my access
points. It's also my friends and family. So I'm in scope

So like I said and tried to give as much proof as possible for, there is only
two ways to use AGPL software: 1) Violate the license. (by not publishing
everything that touches the software) 2) Purchase another license.

(2) is usually not possible. Most software is not dual licensed. (1) is not
really using the license. If you don't agree to the license then you have no
right to it. It's essentially software piracy.

So neither (1) nor (2) is actually using AGPL.

To the extent the software in question is used, it's not used under AGPL.

But I was mostly responding to "so everyone can just buy a commercial license"
(but see (2)), which just means AGPL is only useful insofar as it doesn't
exist.

> Like MongoDB, it selected AGPL from the beginning, and many people were
> using it (so you can’t say AGPL stop people to use MongoDB)

MongoDB is probably the most popular, yeah. Note that OpenBSD still uses
POVRay 3.6, because 3.7 changed to AGPL.

I still maintain that most people who use MongoDB are violating the license,
so they're not really "using" the AGPL.

> until some big commercial companies began to deploy it in cloud and violate
> AGPL (refuse to open source). This hurt the protocol and MongoDB, so MongoDB
> decided to change the license to a more explicit and strict license written
> by themselves to rule explicitly that if you deploy the MongoDB in cloud you
> should be open source

I was not aware of this. So you're saying AGPL failed at the one thing it
attempted to do, which is to plug the so-called "hole" of cloud?

> From this point of view AGPL or the more strict MongoDB protocol find a good
> balance between open source and commercial usage.

"Open source" in the sense that the source is available for viewing? Yes. But
most of the time that's not what that means.

From wikipedia:

> Open-source software is a type of computer software in which source code is
> released under a license in which the copyright holder grants users the
> rights to use, study, change, and distribute the software to anyone and for
> any purpose.

"For any purpose". That's freedom zero, which AGPL doesn't have.

Same with these recent licenses I've seen where the author has said "GPL but
can not be used by the police", due to the author's political views. That's
not what "open source" or "free software" means.

> Please tell me if MongoDB uses more free software style license, like GPL,
> Apache, MIT, I guess many companies will use it in non open source style
> without violating the protocol

Probably yes. I know at least one FAANG company that has purchased a non-AGPL
license of MongoDB. But like I said that's not always possible. And my initial
comment of "nope nope nope" is the legal stance frow actual tech lawyers I've
discussed this with.

But curcially: This is intentional! Open source explicitly allows use _for any
purpose_ , even if that purpose is to interact with non-opensource. That's not
a bug!

> If MongoDB can not live a good life, who will contribute to it, maintain it,
> help user continuously?

But this is two different questions. As I see it AGPL is about politics, not
money. Most AGPL is not dual licensed.

As for maintaining. If you're a company (say Google) that runs GPL software
(say the Linux kernel), then it's better to upstream your patches, _when they
are not specific to your proprietary internal systems_ , than to fork the code
and have to manually apply upstream's patches.

Hell, the BSDs are still alive, and they even allow redistributing the
binaries without providing source code!

The money question is a real one since free software began, but AGPL doesn't
solve it, nor did it ever even attempt to solve it.

> I am glad that google doesn’t like AGPL. To me this implies that the thing,
> that is not liked by big company, could be interesting.

This is a terrible argument. I'm sure Trump also doesn't like it. The enemy of
your enemy is not necessarily your friend. You should look at _why_ they don't
like it, and see if those reasons apply to you.

Google also doesn't like global warming or covid-19, but I don't see you out
there releasing freon or licking ventilators.

Also note that this means none of the, what, 100'000 engineers working for
Google are allowed to touch your software. No, not even contribute to it on
their own time (with one exception:
[https://opensource.google/docs/iarc/](https://opensource.google/docs/iarc/)).
Your community will shrink just because of that.

> AGPL just prevents the big companies , like google, amazon, to use open
> source software for free.

No, it prevents everyone from using it, as described.

Also: Using software for free (in both senses of the word) is literally what
opensource is for.

~~~
jxj
"free software", "for any purpose", beautiful target. But maybe it can not be
achieved in one step.

People select a license for purpose. No matter what is the purpose, the
developer is free to choose, the user is free to accept or deny. If the
license really brings some big hurt, people might change later.

~~~
knorker
Yup. There's nothing illegal about this private contract. I'm just saying it's
a lose-lose license for both parties.

For authors: AGPL is counterproductive to its stated purpose, and will only
drive away users and contributors. AGPL is not "open source" or "free
software". If dual-licensed then you are essentially releasing commercial
software. And that's fine. But own up to that. If not dual-licensed then
pretty much every user will violate your license. So what was the license good
for?

For users: There is no practical way to use AGPL software without violating
the license. Everything you do with AGPL software incurs a huge legal
liability. It is not open source or free software. If it's dual licensed, then
pretend only the other license exists. If it's not, then pretend this software
doesn't exist, and move along.

Actually, there is one way for authors to derive value from AGPL. It's not
ethical, but it exists. Release your AGPL software, and wait for reports of a
company using it. Then sue them. Because they are pretty much guaranteed to be
in violation.

------
nimbius
most of these FPGA's are north of $2000 USD...does anyone know if you can do
something like this with an RTL SDR dongle?

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jxj
2000USD? Not really. Following two options are less than 1000USD:

1\. zed board + fmcomms4 = 883 USD [https://www.digikey.com/product-
detail/en/digilent-inc/410-2...](https://www.digikey.com/product-
detail/en/digilent-inc/410-248/1286-1043-ND/4840855)
[https://www.digikey.com/products/en?keywords=FMCOMMS4](https://www.digikey.com/products/en?keywords=FMCOMMS4)

2\. adrv9364z7020 + crr bob board = 932 USD
[https://www.digikey.com/products/en/rf-if-and-rfid/rf-
transc...](https://www.digikey.com/products/en/rf-if-and-rfid/rf-transceiver-
modules-and-modems/872?k=ADRV9364) [https://www.digikey.com/product-
detail/en/analog-devices-inc...](https://www.digikey.com/product-
detail/en/analog-devices-inc/ADRV1CRR-BOB/ADRV1CRR-BOB-ND/7203205)

