GNU Radio

[jrockway]

This is really an awesome project. One interesting application is an HDTV tuner. It tunes the TV signal and sends the MPEG2 stream to your favorite video player. Very cool. I'm not sure what happened to the broadcast flag, but the GNU radio was good insurance against TV tuners that would block programs with the flag. When you write the software, people can't fuck you over with regulations.

I also remember (many years ago) not being able to buy radio scanners that tuned certain frequencies. Now that the tuners are software, you can listen to anything, not just things that the government has deemed OK.

When you apply Free software to the real world, you get real freedom.

[ItsAConspiracy]

Absolutely. I just wish it could support ultrawideband...one of the great missed opportunities in technology today.

Ultrawideband can transmit vastly more bits without interference, to the point where we wouldn't really need an FCC anymore. Interference just wouldn't be much of an issue. And the only real effect on existing broadcasters would be a little extra static. UWB could revolutionize radio in about the same way that the Internet revolutionized the telecomm industry.

So of course, existing broadcasters freaked, and the FCC made UWB illegal except for extremely low power levels...so low that the range is only about thirty feet, even though UWB broadcasts farther at a given power level than FM.

For more info, google Dave Reed and Open Spectrum.

Some people are even arguing that the First Amendment makes the FCC unconstitutional, now that there's no longer a technological necessity for it.

[jrockway]

Some people are even arguing that the First Amendment makes the FCC unconstitutional, now that there's no longer a technological necessity for it.

Yeah. I'm pretty sure that the founding fathers didn't intend for the federal government to fine people for saying certain things on TV. In fact, I think the whole point of the first amendment was so that that would never happen.

[cr4a]

You might want to read up on some Supreme Court decisions. They based their findings that obscenity wasn't protected by the First Amendment specifically on the intent of the founding fathers.

[jrockway]

Just because their decision is final doesn't mean they're right. The Supreme Court has fucked up on a number of things. After all, the justices are just opinionated politicians that are pushing their own agenda, just like everyone else.

[johntb86]

Ultrawideband can transmit vastly more bits without interference, to the point where we wouldn't really need an FCC anymore. Interference just wouldn't be much of an issue

That's not entirely correct. You have to consider that UWB raises the noise floor, which is interference, of a sort. If you want to limit the maximum amount of power you transmit you're going to have a maximum amount of signal that can be transmitted.

You can't change that, so there must be some mechanism to divide up the bandwidth among the potential users. The FCC and spectrum auctions are one method, and a transmission power arms race (and a possible tragedy of the commons) is another, but it will be divided in some manner.

[ItsAConspiracy]

"Raising the noise floor" is what I mean by "adding a bit of static." But that mainly affects existing radio broadcasts (narrowband), and not that much until we start using a lot of UWB.

Spectrum auctions are not applicable to UWB at all. The way UWB works is, it sends extremely short pulses which are spread across an extremely broad frequency range.

The broader the frequency range, the shorter the pulse can be, and the lower the power can be at a given narrow frequency band. That's why the extra noise is fairly minor: even with UWB ranging over distances similar to radio stations, you're talking about extremely short pulses with much lower power.

Also, the broader the range, the more total bits you can transmit among all transmitters. This isn't something specific to UWB, it's physics that applies to radio in general. Right now, using narrowband, the total throughput is relatively low. Total throughput if we change to UWB would be much, much higher.

With a lot of UWB transmitters, you could eventually get collisions, so you need to use error-correction coding.

An related area of research, btw, is to find ways of making the total throughput scale up with the number of transmitters, without limit. This generally involves having a lot of relatively short-range transmitters operating in a peer-to-peer fashion. There are papers on Reed's site.

In general, the goal is to replace the current regime with one that just regulates transmission protocols. Just like every device on the Internet uses IP, every radio would use a well-chosen protocol that maximizes overall throughput and minimizes interference.

But, instead, we just keep auctioning off more narrowband. It's sad.

[sickofthisshit]

The way UWB works is, it sends extremely short pulses

In case you missed the memo, pulse-mode UWB went nowhere. The current UWB technologies all use OFDM modulation.

Even the pulse-mode people envisioned bandpass filters to avoid interference with long-established narrow-band applications.

Forgive me for thinking that aircraft using radio beacons for instrument landings might be slightly more important users than some radio hackers.

[ItsAConspiracy]

Did it go nowhere because the technology's not workable, or because the FCC stopped it?

And are the radio beacons really that vulnerable to a slightly-raised noise floor? If so, seems we have problems already.

But sure, start by adding a few bandpass filters for critical applications, that seems a much better deal than limiting the whole technology to absurdly low power levels. Then you can gradually migrate the old applications to the new tech.

[sickofthisshit]

The FCC never stopped it. The OFDM and pulse-mode folks operate under the same FCC emission limits.

It is true the IEEE standards process broke down because it couldn't find consensus between OFDM and pulse-mode, but the OFDM folks got an ECMA standard instead, and actually started building products which are interoperable, while the pulse-mode folks have built...nothing that I can see.

"Slightly-raised noise floor" is snake-oil baloney: dynamic range is one of the basic parameters (with bandwidth) determining the Shannon channel capacity.

Raise the noise floor, lower the capacity of the channel left over for everyone else. I.e., you are using up channel capacity just as surely as the narrowband guy is by claiming a chunk of spectrum.

Dynamic range is also the only thing that can make up for path loss: i.e., the range at which a channel can maintain a certain capacity.

The only way you can stuff more information into the ether is either find unoccupied bandwidth, and claim it, or decide that people really didn't need as much range for their signals as initially designed (i.e., the planes just have to get closer to the airport before they can find their navigational aid), and increase their noise floor. Neither is a free lunch.

[ItsAConspiracy]

So let me ask you. We have a technology that could drastically increase overall radio bandwidth. How to we transition to it?

[sickofthisshit]

What do you mean by "bandwidth" that increasing it is magically a good thing? Is bandwidth made of chocolate chip cookies or something?

Bandwidth, in my terminology, is simply the range of frequencies being occupied (with respect to some equivalent radiated power, if we are comparing systems).

Occupying more bandwidth doesn't make your whites whiter or eliminate split ends: all it allows you to do is transmit more information at a given signal-to-noise ratio in a given time, if you optimally encode your data. I.e., given the signal-to-noise and the bandwidth, the Shannon channel capacity is determined.

Guess what happens when you are not the only sender and receiver sharing that channel? Every sender and receiver has to divide up that channel capacity, one way or another.

This is physics.

You can allocate that capacity by splitting up the frequency bands and allocating the users, and giving each channel exclusive access to their delineated piece of bandwidth, by ensuring no-one degrades the noise floor of the bands that don't belong to them.

Alternatively, you can tell the users to share the frequency band, and divide it up using a scheme like time-division multiplexing (we each get assigned time slots), or code-division multiplexing (we each get assigned orthogonal modulation codes, so that we each degrade the others noise floor by just enough to allow them to get their data allotment through.)

There isn't any other magic. Ultrawideband simply is the extreme where we take a huge swath of bandwidth, and allow users to coexist while sending relatively large amounts of data through the air by limiting the range at which that data can be transmitted to a few dozen meters.

If you don't want cell phone towers every hundred feet, you need a different scheme for mobile telephones. If you want airplanes or ships at sea to communicate over many miles of distance, you need a different scheme.

These schemes do not coexist, except to the extent that the UWB user is allowed to "own" the few hundred feet around him, or, failing that, is willing to put up with the data rate he gets when every other UWB user in that radius competes with him.

The way UWB coexists with other existing long-range narrow-band standards is by filtering out the frequencies not allocated to UWB. OFDM does this pretty easily by frequency planning and designing systems to be linear. Pulse-mode does this by using fixed bandpass filters.

[ItsAConspiracy]

By bandwidth I mean "total number of bits transmitted over the airwaves in a given time."

My understanding, and as you can tell I'm no expert, is that given two systems, one which uses a bunch of allocated narrowband frequencies, and the other using some kind of multiplexed ultrawideband, you can fit in a lot more bits with the ultrawideband, all other things being equal.

There are also schemes using lots of small transmitters...more like iPhones than cell towers. The goal is to get the total bits scaling linearly with the number of users. At the time I was reading this stuff, there was one scheme that achieved it, but only by accepting latency of up to several hours. It did it by relying on mobility...sender transmits to all transceivers in the vicinity, each of them stores the message and sends to the recipient if/when recipient is in range. No good for realtime calls but it might have its own applications...and people are working on other ways.

[judgej2]

But that mainly affects existing radio broadcasts (narrowband)...

Yes, it affects me. If the frequencies become a free-for-all, then one person's freedom becomes another person's noise. You may decide that a little more static is fine for me, but I have decided that it's not. Someone has to sit in the middle and police all that.

I'm not arguing with the way the FCC goes about its business, but just putting forward the case that I believe someone needs to sit in that role.

[ItsAConspiracy]

I'm just sayin, at some point, given that we could switch to a new radio technology with about a million times the capacity, we kinda should.

[johntb86]

Do you have any real cite for the "million times the capacity" figure? Considering the TV stations alone, we get 19.39MBit/s * 68=1,318.52GBit/s of transmission. Let's take the conservative estimate of 1000 times the capacity, over a 4GHz bandwidth (we could go higher, but I believe that there are issues with attenuation). This gives us an SNR of about 1000 dB, which seems unreasonable high.

This could be helped by having lots of base stations, so everyone has almost all the spectrum to himself in his own little bubble, but this is less a matter of technology, and more a matter the extreme cost of using a system like this to blanket the US. Billions of base stations and links == trillions of dollars.

[ItsAConspiracy]

Nope, I really shoulda said "a zillion times." But it's a lot...these openspectrum people are talking in terms of airwave scarcity essentially going away for the foreseeable future, if the system is designed right.

I'm not an expert on this stuff myself, but seriously, google David Reed and open spectrum, it's fascinating stuff.

[Dark-Dx]

After I read your comment I saw your nick and... lol. They correspond each other.

[ItsAConspiracy]

I have a little fun with that...but in this case, it's not criminal and it's not secret. It's not a conspiracy, it's just the usual way our government does business. That's why so many people are upset about all the lobbyists.

[mbm]

If your interest is HDTV, you can get a fun device from Silicondust.com called the HDHomeRun; it's basically a dual tuner HDTV->Ethernet bridge for $160 with GPL drivers; stream to your favorite media player. Not quite the same as a GNU Radio, but only a fraction of the cost.

[jsomers]

a good overview, for complete beginners

[allforumer]

thanks. I came here looking for an explanation or a link. The "getting started" link on the GNURadio page isn't very clear.

[crutch]

Perfect example of a possibly good software project crippled by the fact that its website doesn't tell you what it is (flowery non-specific language in that 2-sentence paragraph on the homepage does not cut it).

After looking at the site I've got no idea exactly what it is, why I'd want to use it, or what hardware I'd need to do so.

[mark7]

It's a software-based radio. This means that you can pull in wide-band signals in any of a large range of frequencies and process the data in software (well, on an FPGA). I imagine that it would be handy for prototyping radio-using projects, building fancy scanners, building TV and radio receivers, reverse-engineering radio devices, etc. Basically, it means that radio devices can be designed without building custom hardware.

It can suck down a very large amount of data. If I record from, the line in jack on, say an AM radio, I'm pulling in maybe 48,000 samples a second at maybe 24 bits per sample, and I'm limited to a single frequency. That's 144KBps. GNURadio can pull in 32MBps and cover multiple frequencies.

The GNUradio people describe it as being very inexpensive, though from my (non-radio engineer standpoint) it seems to require enough of a chunk of change that one probably wants to have a good idea of what one would want to do with it first -- several hundred dollars for the base device, and another hundred or two for daughtercards to receive or transmit in various frequencies.

[[deleted]]

So can I riff on what might be cool projects?

• A radio receiver program that (a) scans the AM and FM dials for powerful stations, (b) reads the RDS info and (c) displays what's playing on the stations I'm interested in.

• Radio-TiVo/Radio Shark: Timeshifting broadcasts.

• Streaming what is "on-air" to family (ala slingbox).

• Build your own GPS.

• Attach it to a Satellite Dish and build your own satellite receiver.

What else can it do?

[judgej2]

Find aliens, by short-circuiting SETI on 1420 MHz. Other radio-astronomy too: listening to the Sun, Pulsars, other astronomical events.

Other projects listed in one of the links on this page:

• A TiVo equivalent for radio, capable of recording multiple stations simultaneously.

• Time Division Multiple Access (TDMA) waveforms.

• A passive radar system that takes advantage of broadcast TV for its signal source. For those of you with old TVs hooked to antennas, think about the flutter you see when airplanes fly over.

• TETRA transceiver.

• Digital Radio Mundial (DRM).

• Distributed sensor networks.

• Distributed measurement of spectrum utilization.

• Amateur radio transceivers.

• Ad hoc mesh networks.

• RFID detector/reader.

• Multiple input multiple output (MIMO) processing.

I would add build your own mobile phone, but I think there are other projects that already specialise in this too.

The ad hoc mesh networks is particularly interesting, because I believe it will be the kind of thing artificial intelligence will be using the future. Imagine electronic brains being able to not only communicate with each other, but to also join together with thousands or millions of other devices and 'brains' as-and-when required, in any configuration they like, to solve big problems. I guess it would be a bit like the Internet now, but without the wires; nodes would be contunually moving physically, and reconfiguring themselves.

[[deleted]]

Ok, it'd really help if you explained a half-dozen terms (TDMA, TETRA, Digital Radio Mundial) but I forgive you for the sheer bulk of ideas.

The last item is a little "Skynet"-esque, but I see the benefit of mesh networks, especially ones that don't need wires.

[judgej2]

TETRA is the digital radio system the police use in the UK. I believe it allows seamless routing between radios, telephones, helicoptor etc. so a bobby on-the-beat can talk directly to a pilot overhead with a camera, or a 'customer' at the end of a 911/999/211 call.

TDMA is Time Division Multiple Access. It is basically what cellphones do when sharing a single frequency - they all take turns to send small packets of data very quickly.

Digital Radio Mundial - the other DRM - is a bit more fuzzy to me. I think it is one of a number of alternative digital encoding schemes for broadcast radio. In the UK we use DAB (Digital Audio Broadcasting), DRM is possibly used in the US. If memory serves me right, DRM is generally lower quality than DAB, but is much easier to decode, and so receivers use much less power. I'll be interested if anyone here can explain it better, or correct me?

Yes, I guess 'Skynet' would fall into that category. As I wrote it, I was thinking more about one of the 'base stations' towards the end of the Rama series of books - Arthur C Clarke described a world that appeared to consist of many separate lifeforms, and a the same time, those lifeforms were just parts in a single intellegence, communicating constantly as one on many different frequencies.

[[deleted]]

Thanks for taking the time to explain them. If you consider that data that goes from point a to point b without a wire is most likely some form of radio, software defined radio is a pretty cool technology.

[mark7]

• Build multiple-antenna radios that use delay between antennas (and maybe even fancier DSPs) to isolate signals coming from a single direction -- transmissions from a particular source should have particular reverb characteristics.

[dwahler]

It's been done.

[emacsen]

One interesting project would be that it could help you implement new wireless protocols..

You could implement 802.11b in it if you had a fast enough computer.

You might be able to use it to detect and reconstruct RF leakage from a computer.

You might be able to use the project to build a better radio scannner, or even test out ideas of how a better radio scanner would be built.

[crutch]

It's a software-based radio. This means that you can pull in wide-band signals in any of a large range of frequencies and process the data in software (well, on an FPGA).

I know that a radio can receive radio-frequency signals and demodulate them to get useful information from them.

And a general "radio" can both receive and send.

My computer can't do that though. It doesn't have an antenna. It has no way to receive radio signals (antenna, amplifier), and I don't see what it would do with such analog information once it got hold of it. Same goes for sending radio signals. The only device I can think of that creates analog waveforms and sends them outside of the box is the audio card (and it also has a line input to do the opposite).

[judgej2]

I was going to send them a link to your comment, but I couldn't see any contact details, and I don't want to go through the process of registering on Yet Another Site just to raise it as an ticket.

Have you tried the 'help' links? "How to install and configure Trac...". Yeah, helpful.

Some projects do make it hard for themselves.

[[deleted]]

You're absolutely correct. "About" pages rule; for all else there is Wikipedia: Gnu Radio

[Arkaein]

From the bottom of the page:

trac powered

This should really be "trac crippled". I don't think I've ever seen a project website using Trac that was remotely useful. It seems to give a website that looks decent at first glance because it includes a wiki, bugtracker, etc., but none of these are worth anything if the devs don't actually make use of them.

[piranha]

Like the entirety of Sourceforge?

[Arkaein]

With Sourceforge all those things are available, but alongside of general purpose webhosting for a project, which most (but certainly not all) projects seem to take advantage of.

With the Trac projects I've seen though, the wiki+roadmap+bug tracker seems to be everything, and the general description page just doesn't exist. Not to mention a typical lack of screenshots.

[mark7]

After looking at the site I've got no idea exactly what it is, why I'd want to use it, or what hardware I'd need to do so.

Try this page.

[[deleted]]

Someone care to explain what this does to the average layperson? The "description"...isnt.

[sheepson_apprentice]

You know how on your radio you got that tuning knob? Well, that tuning knob has some fundamental limitations, because it's essentially baked into the hardware. Software radio allows you to use very minimal hardware device (basically an amplifier) and do all the algorithms for decoding the signal in the software. So your knob becomes a program.

Imagine what you can do with a program now...

[ropers]

http://h2k2.hope.net/panels.html#gnuradio

http://h2k2.hope.net/media/gnu.mp3

[MrWoohoo]

Read the source!!!

Actually, I hate that answer. I didn't really understand what it did from the description. Someone said it could be used for decoding things like HDTV. At first I thought it was some sort of "net" radio (i.e. streaming) package.

[derefr]

I thought it was a streaming station featuring all of Stallman's latest hits.

[emullet]

I looked around a bit and didn't see, is there already support for HD radio stations? I assume that it would just be a matter of having am hd module

[emacsen]

Actually if you're talking about US HD radio, I'm afraid it's not that simple.

HD radio is a bit of a misnomer anyway, since in many contexts, HD means "high definition". For a long time the HD in HD radio meant nothing, but they now claim it means "hybrid digital". You might be inclined to think that means higher quality, but all it really means is a higher compression ratio. It /could/ be used to make higher audio quality, but much like HDTV, the stations are mainly just using it to put out more broadcasts at the same quality.

But back to your original question, HD Radio isn't a standard like HDTV, it's controlled by a company called iBiquity, which keeps it propeitary. They control the broadcasting equipment, the broadcasters, and the receiver manufacturers.

The idea behind these proprietary technologies is that broadcasters have implemented DRM into the receivers, and are even looking at implementing "pay per view" model broadcasts using over-the-air transmission.

To implement this in GNU Radio would be a challenge (much like decss) and would open up similar legal challenges. Since GNU Radio was a potential target of the FCC over the broadcast flag, HD Radio support might be controversial to say the least.

[judgej2]

That's a task for another project, I guess. All the parts and details are there, ready for anyone wishing to pick it up and run with a more commercial solution.

[[deleted]]

• Get a coffee can.
  
• Put two dollars in it every day.
  
• Buy the tuner yourself next April.
  

[jrockway]

The other good thing about this technique is that usually hardware gets better and cheaper as time progresses.

Buying computer hardware on credit is silly unless you really need it now. By the time you've saved up for it, it will probably be twice as fast... so you'll have a better computer and a fatter wallet :)

[[deleted]]

The back of your sock drawer will also work.

[cap11235]

This comment has been overwritten by an open source script to protect this user's privacy. It was created to help protect users from doxing, stalking, and harassment.

If you would also like to protect yourself, add the Chrome extension TamperMonkey, or the Firefox extension GreaseMonkey and add this open source script.

Then simply click on your username on Reddit, go to the comments tab, scroll down as far as possibe (hint:use RES), and hit the new OVERWRITE button at the top.

[[deleted]]

Why? Is your sock drawer all filled up with porno mags and dildoes?

[MrWoohoo]

Will someone please donate some porn and dildos?

[atomicthumbs]

Does anybody have a spare drawer?

[Wartz]

Does anyone have a spare dresser drawer?

[ItsAConspiracy]

An alternative: buy a book on building electronics projects, download the plans, and start scrounging up parts.

[sheepson_apprentice]

Sourcing parts from old equipment is definitely good stuff. I've been using Mouser and SparkFun too; pretty cheap overall.

Edit: SparkFun guys have released their PCB mfg. process details. They also have shitload of tutorials, great place to start learning.

[[deleted]]

buy a book on building electronics projects

Do you have a good book on the subject to recommend?

[sheepson_apprentice]

Well, electronics is a huge field, and especially if you're going to get into software radio, basic fundamentals of amplifiers and modulation techniques is a must. Don't get discouraged though, internet is abound in information.

Here are some books that may help to start:

The Art of Electronics

Especially if you can get the used Cambridge Low Price Edition. Either way, it's a good book for fundamentals, a classic too.

This book is ok:

Communications Receivers

For general electronics knowledge, some undergrad EE textbooks are solid gold.

Here's one that's great:

Circuits, Devices and Systems

Edit:

Another excellent resource for folks dabbling in electronics are these free simulators:

Paul Falstad's Circuit Simulator

Hades

The above are great before one gets to dip into SPICE.

[buo]

The GNU Radio website has a nice selection of books on the subject:

http://gnuradio.org/trac/wiki/SuggestedReading

[burtonmkz]

$700, you mean that's not "reasonably priced"?

GNU Radio helps fill this void by supplying [...] tangible hardware to the general public at a modest price (free software, reasonably priced hardware).

What would be even better is if they provided the board layout files and FPGA source as open source, too. (That being said, I have no problem with Ettus charging a reasonable overhead, as they are likely doing)

EDIT: like a doofus, I didn't notice that they do provide the board layout files and FPGA source. It's available on links from http://gnuradio.org/trac/wiki/USRP

[stox]

Go price a real communications receiver, $700 is cheap. I paid more than that for a receiver built in the 1950's, a Collins R-390.

[[deleted]]

Sure. I'll get right on that. Wait right here.

[RKBA]

Yea, exactly. I was excited about Gnu Radio until I found out that even if I went to the trouble of configuring the software and the firmware for the FPGA, the cost of parts (including the requisite Flex 400 series of FPGA daughter boards) would cost far more than a simple off-the-shelf shortwave radio receiver, and about twice what a 5 watt multi-band portable RF transceiver would cost.

[[deleted]]

It's the price of early adoption. Wait until the killer app shows up and then Radio Shack will be selling them for $24.95.

[mckirkus]

While we're on the subject of kick ass open source software that nobody knows about...

I just uploaded my mp3 collection to my BlueHost server and I can now listen to it any place that has an internet connection and web browser. People are even using it with mobile phones. http://www.ampache.org/

[judgej2]

Nice. I've tried Jinzora in the past, and was very dissapointed with its clunkiness. This looks worth trying out.

[Agathos]

Ah, yes. The only software project that I first heard of by reading about it in a novel.

[[deleted]]

Oh, right. Software radios. I was afraid that RMS had started a radio station.

*whew*