Software-Defined Radio Could Unify Wireless World

mjdroner writes "Technicians in Ireland are testing a device capable of skipping between incompatible wireless standards by tweaking its underlying code. The article states: 'The device can impersonate a multitude of different wireless devices since it uses reconfigurable software to carry out the tasks normally performed by static hardware. The technology promises to let future gadgets jump between frequencies and standards that currently conflict. A cellphone could, for example, automatically detect and jump to a much faster Wi-Fi network when in a local hotspot.'"

Comments

GNU Radio

[mukund]

Perhaps GNU Radio is of a worthy mention here.

A plug for GNU Radio

[InterruptDescriptorT]

Since we're talking about Software Defined Radio, I urge everyone with an interest in the subject to look at the GNU Radio project. They have designed a front end board using generic cable TV tuners feeding an FPGA to perform some initial processing, such as decimation and filtering. The data is then transferred over USB to the host, whose software performs the demodulation and decoding. It's a fascinating project and a great stepping stone into the field.

To really get started on SDR, check out the Ten-Tec RX320D shortwave receiver. It outputs a 12 kHz-wide IF signal from the front end to an audio jack, which can then be fed to a PC soundcard. There are a number of packages that can take this data and demodulate it, including DREAM, an open source DRM (Digital Radio Mondiale) decoder which allows you to listen to the new digital shortwave transmission standard that many of the world's broadcasters are beginning to experiment with.

Re:A plug for GNU Radio

[leighklotz]

Why spend that much ($350+), when you can order a dirt-cheap shortwave radio for maybe $40 and just use a simple 455 kHz to 12 kHz adaptor?

SDR is a broad topic. Wide-band digital modes such as the 12KHz wide DRM or even narrow ones such as HamDream are a simple example.

SDR involves a variety of techniques, but the basic idea is using an A/D at an early stage, and performing operations traditionally done with RF components with DSP software instead.

In its extreme, an SDR has a broadband RF amplifier and a DSP.

Some systems use a tuned RF filter before the RF amplifier to improve dynamic range and reduce overload, and others put the DSP after the first analog mixer. Ham equipment that uses IF DSP does this, such as many of the ICOM radios.

Then there are devices that then mix down to somewhere around the audio range, at least to the 0-96KHz or 0-48KHz range handled by many popular PC sound cards. The RF signal is detected by a an I-Q detector, which produces two signals In Phase and Quadrature (90 degrees out of phase). You might notice that this is a decomposition of a periodic wave into real and complex parts, given v=cos(omega)+j sin(omega). Thus, DSP techniques such as FFT can be applied in the complex domain. If you're seriously interested in this math, look up the Hilbert transform. It lets you modulate or demodulate directly in the DSP, and as a result the transmit and receive software and hardware are very similar. (And wouldn't the Professor on Gilligan's Island like to know that you can make a receiver into a transmitter without using coconuts!)

Anyway, once you get the I-Q signals into the two channels of the sound card, you get a view of the RF spectrum all at once, up to the bandwidth of your sound card sampling. So, if you have a 48KHz sound card you get 48KHz of band scanned simultaneously, and can pick and choose what frequency you want to demodulate, and how you want to demodulate it in software (AM, Single-Side Band, FM, various digital modes such as the aforementioned DRM=digital radio mondial). See here and here.

The SoftRock 40 and its replacement, the SRv5, surface mount kits costing in the $30 range, do this. They're an excellent introduction to SDR techniques, without requiring DSP chip programming. People are doing fun things with them. It's not a transmitter yet, but it will be soon with another board and a ham license).

For software, among others, there is Gnuradio, and also SDRadio, a Windows app. And there's DTTSP, a SourceForge project that runs in Linux and also releases a DLL used by the FlexRadio people. DTTSP has a number of front ends in development, in Java and other languages.

A step up is the FlexRadio SDR-1000, alluded to above. It's a 100W transceiver that does the same thing that the SoftRock does, but does a better job, and also use a VFO that allows it to pick what frequency range it operates on, rather than being limited to a particular crystal-controlled band as the stock SoftRock does. It also costs quite a bit more, and they use a 96KHz sound card to get good quality.

Here's the big deal

[TubeSteak]

The underlying technology has the potential to revolutionise wireless communications but has been difficult to test outside the laboratory until now as the majority of the radio spectrum has already been allocated. Licences are normally limited to a particular radio frequency and modulation but the one issued to CTVR permits a device to hop quickly between many different standards.

The CTVR trial will also test how easily frequencies can be dynamically allocated to different devices. One idea is for companies that own a licence to automatically "sublet" access depending on demand. The licence [to trial the software radio] means we will be the first research centre in the world to practically investigate the commercial potential of dynamic spectrum-allocation,

Re:Great

[jc42]

[I]t used to be that only the military could fark up my garage door opener. Now everybody will be able to.

Heh.

However, to put it in perspective, we should note that this is directly in line with the original design, back when the Internet was called ARPAnet.

The funding came entirely from the US Dept of Defense, and if you dig up the early ARPAnet docs, you'll find lots of diagrams of military scenarios, with everything communicating via wireless links. This makes sense, of course, because you really can't tie together tanks, jet fighters, aircraft carriers, etc. with wires.

If you read the docs, you'll find that there was a strong emphasis on automatic reconfiguration, as the enemy shot down your comm equipment. Routes were to be reconfigured dynamically. The network was to use whatever comm equipment was available. It was to use whatever frequencies were usable to get the data through.

But primarily, as things got shot down, everything was supposed to constantly monitor the electronic environment, and dynamically reconfigure itself so that it kept working.

Now it's four decades later, and people are coming up with the same ideas, and pushing them as something new. Except now the "enemy" is the FCC and the corporations that want to control their part of the spectrum and block access to the competitors' equipment.

Maybe some day we'll actually get what was conceived back in the 1960's.

Re:antennas?

[SuperQ]

Antennas only affect the shape of the RF output, and the frequency range at which you can efficiently radiate.

Take some examples:
Omni-directional wifi antennas on most APs: a single stick with a fraction of the wavelength of 2.4ghz. Very simple, can do anything from SSB, AM, FM, or OFDM modulation.

Most of what software defined radios is talking about modulation changes, not frequncy changes.

The only difference between 802.11b and 802.11g is the modulation (CCK vs OFDM)

Re:antennas?

[satguy]

I understand how you can use software to replace some of the active circuitry, but how are you going to change the size and shape of an antenna via software?

You don't necessarily need to change the size, you need to change the resonant frequency and impedance. This is currently done with 'automatic' antenna tuning circuits using varicaps and other components/switching circuitry that varies the resonant frequency by varying bias voltages.

Re:Software radios a step towards real deregulatio

[SagSaw]

Sure, some people will say "What prevents Megacorp YYY from blasting 100,000 watts over every frequency?" That's pretty simple -- energy costs make it prohibitive to transmit anything but profitable data.

No, it's not practical to blast 100,000 watts over ever frequency. I'm not worried about such a shot-gun approach. What I'm much more worried about is the "sniper" approach. Let's say that you're using the newly-deregulated spectrum to provide some service. Perhaps your trying to operate a local public interest radio station, or providing internet service, or selling wireless telephone service of some sort. Now somebody with an interest in preventing _you_ specifically from providing your service comes along. Maybe they don't like the message from your radio station, or are your competitor in the ISP/phone market. All they have to do to keep you off the air is tranmit a signal which degrates the SNR of your signal sufficiently to render it useless. If they're willing to pay a little more for the power to produce their signal then you are for the power to produce your signal, they'll win.

I'd much prefer minimal regulation (i.e. just enough to force licensees to co-operate to avoid and resolve cases of interfearance.) to no regulation.

Cap max. wattage allowed & ban delbrt interfer

[Anonymous Coward]

What prevents Megacorp YYY from blasting 100,000 watts over every frequency?

Well miscreants may do it .. or well political groups may do it to silence broadcasts etc.

It's better to simply ban intentional misuse and place a wattage cap for license free broadcast. Also open up more spectrum for WiFi and devices that are non parasitic (fine people who don't follow spread spectrum rules etc. if they are broadcasting above a certain wattage).

I would really love to live in a world where all that analog TV, digital TV, analog radio, digital radio, CB, HAM and every other heavily regulated piece of spectrum could be allocated to being used for just information transmission.

That's the way it is today. Except a corporation known as government owns it and uses / rents it out to make money. Shareholders in govt. are called "taxpayers". You are pro entity ownership right?