Ask Eric Blossom about Software-Defined Radio

Eric Blossom is an electrical engineer with a history of working with radio and communications security. He gave a presentation at the recent H2K2 conference about his work with GNU Radio, which is, bar none, the single most exciting software project in existence today. (Imagine computing devices that communicate seamlessly across the entire electromagnetic spectrum.) As usual, we'll forward some of the best questions to Eric and post his responses when we receive them.

Comments

FCC vs. Software Radio

[minddog]

I was recently at H2K2 and heard this forum which right away made me ecstatic(sp?). An issue that was brought up was how this can impact the DMCA, FCC, and the big corps. You guys were saying Sony, and the other conglomerates were forming a committee that would do a digital signature to say what was allowed to be copied, and not through a dual channel checking...My question is what is the status of digital radio and its rights in the present world? To my understanding you can have a very high number of digital channels inside a single band which makes licensed analog frequencies just a waste of money to corporations if they use GNURadio as a means to transmit data long distances. Anyways, looking forward to some feedback and goodwork, I'll be joining this revolution soon, just got the dual server built ;)

Re:FCC vs. Software Radio

[killthiskid]

I'm thought something along the same lines... used to be that any RF that came into a person's airspace was fair game... now that's not true. It can be illegal just to 'listen in' (esp. if it involves decrypting the signal).

It seems to me we're moving the complexity away from expense to duplicate hardware into 'free' to duplicate software. With the increase in power and decrease in cost of general purpose (programable) electronics (i.e. CPU, radio recievers, ADCs, etc), one person can write complex software that can then be used to utilize the (relativiely) inexpensive hardware.

Once you have the hardware setup, you can change the software and:

• Listen to police band.
• Listen to cell phone.
• Listen to XM radio
• Listen to satelite transmissions
• Listen to military communications?

Hardware requirements

[wowbagger]

The GNU radio page is a little thin on the hardware requirements to run the code - could you spell them out?

I realize this might be complex, and that the answer might be of the form

to demodulate a 16QAM signal at 115.2kBaud, you would need an XYZ digitizer card reading the 455 kHz IF and a AAA GHz Athlon CPU. To recover standard multplex FM, you would need a 123 digitizer reading the 455 kHz IF and a BBB GHz Athlon. To decode GSM you need a FFF digitizer reading the 10.7 MHz IF and a quad Athlon.

But as both a ham and one who designs SDRs, I'd like to know where this resides on the Home Hacking Scale....

Sounds familiar

[FreshMeat-BWG]

As in WinModems doing the modulation/demodulation. These devices were a nightmare. After trying several I went back to a good old hardware-based-modulation modem.

Are there parallels to this technology? and if so, how will GNU Radio avoid those pitfalls?

What external hardware?

[Consul]

I read through the GNU Radio website, and even though I found it informative in terms of the basic idea and examples, I couldn't find anything relating to what extra hardware is needed. (Maybe I just didn't look long enough?)

What extra hardware is needed in addition to a computer? Are we talking DSP chips and boards, or something a little more exotic?

Thank you for a potentially exciting project, though. This makes me want to renew my ham radio license. :o)

Work Arounds

[haplo21112]

With the restrictions to broaccasting on the internet that seem to be spring up by the day do you think this tech can become a work around. In otherwords most restrictions ar based on the faact that its the audio being rebroadcast. Perhaps is it were the Stations actual signal being broadcast across the net and recided by a capable piece of software, many of the restrictions would no longer apply. Since its the carrier signal taking the content to my computer rather than an audio codec. This would negate most of the complaints that have caused many internet radio stations to go offline....

Your thoughts?

GNU Radio vs Motorola

[Gekko]

What work has been done with the DoD. Can GNU Radio realistly be expected to compete with the likes of the Motorola DMR in the Defense sector?

You can transmit radio signals without speakers to

[Anonymous Coward]

Using speakers to transmit the signal is of course the simple way to go about creating software radio transmitter and receiver, but not the only one. This software, called Tempest-AM (and I hear Frequency Modulation is coded too, though not released) creates a pattern on the monitor screen which causes the monitor to transmit radio signal on the selected carrier and frequency. The software could be used to transmit data as well, at least if a bit more novel modulation would be employed.

Describe your dream hardware for a software radio

[geirt]

I want a feature list containing all the geeky details

• Frequency range.
• Bandwidth (do you want to sample the whole FM band (or GSM/GPS/CB/ham bands), or just a single channel/station).
• Sample frequency and depth (ie, fast and few bits, and do decimation in software or slow and many bits with less CPU overhead)
• Necessary spurious free dynamic range, or some other dynamic range specification.
• Interface to the PC (PCI, firewire, USB ...).
• Antenna connector (OK, I know that one: BNC)

Radio design is about trading features against each other, eg. if you want a large frequency range, you will usually end up with noisy oscillators giving you poor large signal handling, and low selectivity (ability to listen to weak stations close (in frequency) to a strong one. If you want good sensitivity, you loose large signal handling. If you want narrow filters, you get lower sensitivity (ok, this is a software radio, so you can do extra filtering in software, so this might not apply). You get the idea. Always compromises.

Re:Bar none?

[Wumpus]

With CPU cycles being as cheap as they are now, and with most desktop systems being ridiculously fast for what they're asked to do, I could think of a few interesting things you could pull off with something like this.

Hook your computer up to your digital cable system, and have it do the QAM demodulation. Then, pump the results to an MPEG transport demux and MPEG decoder. Boom. Instant digital cable box.

Same thing, in reverse. Output IF, and hook it up to an upconverter and amplifier. Now you're your own cable company. The equipment typically used to do this is insanely expansive, and hard to get. This can make community cable television, for example, much easier and cheaper to implement.

Interestingly, the decoding/encoding is all done on a commodity, general purpose computer, so all copy protection schemes become hackable, the way they were with software DVD players.

More importantly, software is easier to fix and upgrade than hardware. This could result in significant cost savings for people who want to use this kind of technology commercially. ...and, having said that, this is not a new concept - winmodems have been doing this for a while now.

Some explanation of what can be done with this

[eyefish]

After reading some posts, some people seem to be a bit confused as to what this is and how it can be used. Well, for the /. crowd, here's a specific example which will put all this into perspective:

Now that generating waves becomes a software problem, it means that theoretically anything that before needed hardware to modulate/demodulate (or encode/decode, depending how you look at it) signals can now be done in software. Practially, this means that you can transform your machine into a WiFi or Bluetooth system by simply installing the right software. It also means that as new future wireless technologies emerge, your hardware can support them by a simple software install.

Similarly, anything that uses radio waves can be "emulated", like a good old FM/AM radio (the website has sample code for this), a Walky-Talkie, a home wireless phone, or even a cell phone!!!

So now you see why there's a lot of exitement around this. If the project could only get more funding (Intel? AMD? IBM? Sun? Motorolla? Sony?) to speed this up...

applications

[mountain_penguin]

In the future will this project let me do the folloing.

Watch digital TV
Listen to digital radio

and analog of the above
using just my PC and an inexpensive cature card eg bt848?
what about encryped signals will systems like this be able to brute force encrypted digital TV/ cabel/satterlite chanels?

UWB, remote communications

[Anonymous Coward]

Hi, I've read a few snippets about Ultra Wide Band (UWB) which sound really promising. Could you please comment on UWB?

Second, what is the bandwidth limitations of the SDR in the GNU project, if any? Audio?

Finally, I want a duplex link to a remote device (more than 100 miles away) that I can send commands to and get back data such as pictures from a digital camera. Low bandwidth in the link is OK. What would you suggest?

Regards,
Chip

...what it means to business

[jukal]

this thesis work gives some insight, summarum:

• new capabilities and applications
• principal limitations: A/d converters & processors
  
• SR disrupts the traditional value chain:
  - dedicated semiconductors vs general-purpose processors
  - Vendors vs OS designers and software programmers
• Cellular industry: Cost reduction > 30%, new business models, promotion of VMNOs & improved roaming
• Regulatory impact:
  - short term: certification
  - long term: standardication & spectrum management

Hardware patents?

[cornice]

Up until now, free software has mostly threatened closed commercial software. GNU Radio, however, might make some hardware manufacturers squirm a bit. If I can use a generic device along with GNU Radio to emulate a range of devices how will this impact the makers of those devices and are you (or users of GNU Radio) possibly violating patents for some of those devices? It seems that GNU Radio will stir up more mud in the IP and DRM debates. What are your thoughts on this?

I read what GNU Radio about, but what's it about?

[Anonymous Coward]

Will GNU Radio serve as an open source engine of sorts to facilitate the decoding of live signals like POCSAG, FLEX, MDT, RTTY, etc..etc.. for developers who want to focus solely on decoding the protocols without the bother of doing DSP, or is this there a bigger picture? How will GNU Radio receive signals to process? What will be the requirements of the DAC equipment to be support under GNU Radio?

Question for Eric

[Anonymous Coward]

How does this project relate to other Open Software defined radio projects such as the ARRL digital radio group and the Tuscan Amateur Packet Radio's Software Defined radio project?

Can you give us more information on the goals of your project in relation to the goals for these other projects? Thanks.

See http://www.tapr.org/tapr/dv/index.html for info on the TAPR digital voice group. Go to http://www.arrl.org/announce/reports-0107/digital. html for a report from the ARRL committee.

Jay Sissom KA9OKT