Introduction to GNU Radio
What is the GNU Radio Project?
The normal way of implementing waveforms and radio functions is having hardware-based
systems do all the work. Generation, modulation/demodulation, alter functions, up/down-
conversion of frequencies, everything is done with electronics in some way. Therefore, there
are some limitations to what a specific machine can do. For example, your normal FM-radio
in your kitchen knows how to do exactly one thing, convert FM radio waves into sound you
can listen to.Now imagine a radio technology that can turn your kitchen radio into a GSM telephone,
or a GPS receiver, or maybe a satellite communications terminal. Or why not a garage door
opener? Thats exactly the opportunities that emerge with software radios!
Straight From the Masterminds Themselves:
Eric Blossom and Matt Ettus on cccamp 2007
Presenting on GNU Radio and the USRP2
Matt Ettus on TechTV
Talking about Software Radio – Gnuradio
Watch (youtube)
The GNU radio project was the brainchild of Eric Blossom, who wanted to create a software HDTV receiver… He teamed up with Ettus, but they lacked a radio platform that was cheap enough… Ettus secured National Science Foundation funding through the University of Utah to design what would become the USRP.
The idea behind soft-radio is that you grab a signal from the air and use software to ‘decode’ it instead of hardware. So all decoding becomes an issue of software and not hardware.
You can grab an FM signal from an antenna, use some software ’stuff’, and get your favorite local
station to come out the computer speaker. The only hardware you need is an antenna and a frontend
to pump the signal into your computer. This device is that frontend interface between the RF capture
device (antenna, dish, etc) and the computer, via a USB2 plug. The reason it was developed was that
this kind of hardware was either very specific (grab only FM signals or TV signals) or very expensive
(the cost of a new computer or two).Geeks will lament as not only is this device a reciever but it’s a transmiter as well. Want to
make an ad-hoc WiFi-like network on some other frequency? What about a smart ‘cell’ phone that
makes it’s own network so you don’t need a common provider (think p2p phones)? As it’s so new,
the possibilities have not been well thought out, but technologies like this are a solution
looking for a problem, kinda like the PC in the 1980s.-Anonymous on Slashdot
Some More Resources:
GNU Radio – An introduction(PDF – 3MB) Eric Blossom answering questions on Slashdot(HTML – 500KB) Reddit Comments on GNU Radio(HTML – 300KB) |
1on1 with Eric BlossomGNU Radio: Free Software Radio Collides with Hollywood’s Lawyers (Eric Blossom)Mark Petrovic interviews Eric Blossom on GNU Radio |
All modern ham radio transceivers connect to computers anyway, so the connectivity
between radio and computers is already there and has been for a long time. That’s
not the real innovation. The real innovation here, with SDR technology, is that modulation and demodulation of radio signals is conducted via software, instead of hardware.Traditional radio transceivers work like this : receive the signal, then pass it through
another circuit that demodulates. For transceivers that can receive AM, FM, USB, LSB, CW,
there are separate demodulation circuits for each mode of modulation. Then, after
demodulation, the signal is usually passed through filtering and DSP (digital signal processing)
circuits that clean up the signal and aid in reception of weak signals. All that crammed into a single traditional transceiver adds up! Most amateur radio transceivers range in price from $1500 – $10,000, simply because of the complexity involved.Enter SDR. Instead of having all these individual circuits, an SDR radio can have 1 circuit,
yet be capable of everything a traditional transceiver can do. Receive the signal, downconvert
it to a frequency range appropriate for digital sampling via an ADC (analog to digital converter),
then perform all demodulation, filtering, DSP, etc. within software!The USRP covered in the wired article utilizes it’s own ADC chips capable of sampling wide
bandwith signals, such as “wide FM” (broadcast) and HDTV. Such chips are expensive, and thus, contributes to the $500 cost of these SDR devices.-csb92376 on Digg
How Do You Start?
You’ll need a frontend hardware to capture the signal, preferably the USRP (which could cost as much as $1500 with daughterboards), a regular computer to connect it up and run the software on, and finally the software, GNU Radio (which is a free download) and you are ready to begin! But before that check out some of the applications that GNU Radio and the USRP were used in.
-anon
