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Technology

Software Defined Radio Systems 60

Posted by timothy from the intelligent-systems dept.
sundbug writes: "Very good article on CommVerge about a new technology called Software Defined Radio Systems. Pretty cool to have one computer receive and potentially send over several protocols."
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Software Defined Radio Systems More

Software Defined Radio Systems

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  • Is it just my browser, or is there a monkey in the middle of the text on that web page?
  • You know, this would be wonderful. Now all the l33t h4x0rz don't need to buy a $200 radio scanner to know that the FBI is coming to take them down for cracking that zip file full of pr0n the night before. Think about it. You could tune in to your neighbor's cordless phone and listen to them battle it out. You could tune in to the chick down the street and listen to her steamy tales of PK on UO/EQ/AO. All in the privacy of your own home! But, then again, where would the limit be? If there were no frequency limit, you could listen to about anything! I suspect that the whole thing of ownership of radiowaves would come up (but their radio waves cross into MY property, I'm ENTITLED to listen in on the phonesex going on next door...). I suspect a move to phones that are corded, with a double-shielded cord. Or a phone that uses 256bit encryptation.
    • A bit about legal control over radio frequency -

      The frequency spectrum is considered a "natural resource" and is public property. The FCC was granted control over the allocation of this spectrum in the Communications Act of 1934. You can license frequencies from the FCC, but you do not gain ownership of them. Location has nothing to do with the control over the frequency spectrum. It is within the FCC's authority to limit the rights to monitor signals within certain frequency bands (whether or not it is enforceable is another matter).

      I am not necessarily advocating the state of affairs, but it is the law of the land. Since I am of course oversimplifying, you may want to check out the issues raised here [cato.org].
    • Most "cordless" phones (ie. a base station that plugs in, and a cordless handset, as opposed to a mobile phone) use a base station frequency around 1.8MHz.

      A slightly tweaked AM radio can tune it. Car radios are best for this, because they're much more sensitive.
      • I used to have a shitty $50 scanner and I could pick up people all in my neighborhood who had anything less than a 900MHz phone. Pretty interesting conversations, including one regarding Slashdot. I live in a pretty small town (Norris, TN) near Knoxville. The funny part was that the people I heard were like, rednecks. They were like, try dubyahdubyahdubya dawt slashdot dawt org, seeh if yewh can read that page! Aside from the usual teenage sex, death threats, and political arguments, not much was to be heard over Norris' airwaves. Yeah, I know you don't really OWN them so to speak, but if they took away your right to listen in on radiowaves that went into your property, you could be arrested for looking at your neighbor in his yard.
      • 1.8MHz are you kidding me???? Cordless phones are in a couple places. Older style ones are in the 40MHz range (around 42 and around 49MHz). Newer style have chunks in the 900MHz range, probably a few more places as well, I don't remember.

        Cell phones are 900ish for analog and well above that for newer digital ones.

        I've never seen an AM phone so even if you could tweak your AM readio it'd sound all funky since it's a narrow FM signal (so it wouldn't come thru on a regular stereo very well or at all since they use a wider bandwidth). New ones are also starting to go spread-spectrum so that reduces the chances of listening in to virtually nil.

        Trust me, I've got several scanners and the phone calls come in loud and clear (even the cells on my older pre-ban rig)

        As for it being illegal...I find it difficult to understand how the government claims it can tell me if I'm allowed to receive an electromagnetic wave that just happens to be bouncing around the air.

        Frankly, if they don't want me to listen they should use better encryption (which they are). Not that I listen anyway. I don't think it's really right to do it and besides people's phone calls are boring anyway. But I think that if there was more of an effort to get people to realize it's even possible to listen (I've shocked a LOT of friends by showing them how easy it is to do...) then people would quit using their crappy analog cordless phones and it wouldn't be an issue anymore anyway.
        • Maybe they're different in the US. I did see one that used 49MHz *years* ago. This was one of the first ones, and had a push-to-talk button like on a conventional transceiver.

          In the UK, at least, older analogue portable phones used 1.8MHz from the base station to the handset and 27MHz from the handset to the base.

          Now, of course, they all use DECT on around 900MHz. It's digital so much harder to eavesdrop.
  • This would be a sweet toy if they could get it in say USB and for under $200. This would replace any type of scanner anyone would want to use, and let you have a lot of fun to. Unfortunatly, this will not happen. Unless someone hacks the unit and gets a nockoff out on the market.

    Just think, Private Video broadcasts (like X-10), TV, Satelite broadcasts, Police, Military, aircraft, cell phones, coreless phones, FM radio, Racecar Cams, HDTV, WI-FI, and so on. All from one little box on your PC/laptop.
    • Oh, I forgot, Mobile News vans. So you can see the true panic of the field reporter when they are off the air, you know, like when you see the fools on TV standing in driving rain and lightning telling us, "Yes it is windy and rainy durring a hurricane, and there went my glasses..."

  • harumph! (Score:1, Informative)

    by Anonymous Coward
    What a bunch of fluff. It pisses me off when an MBA walzes in & their genius revelation is that it would be nice if "everything worked together". Fundamental differences at all layers of the OSI model, combined with competing technologies that won't open up their systems make this vision unobtainable. Yeah, let's weave together this short range wireless token ring network with this IP net - all we have to do is NAT all boxes in the token ring net. Then we have cell phones - don't have any IPs for them, guess we want them to talk IPv4 since the rest already is - NAT them too. Shit, is the garage door opener supposed to be on this magical pixie network? Screw it, time for IPv6 - OK everyone, upgrade everything you have to talk IPv6, and you garage door opener manufacturers schedule a tech meeting with these cellular manufacturers over here because your frequencies overlap. What were we doing again? oh yeah, trying to get actual work done at the nodes instead of playing with the paths.

    Nice suit. Get out of the engineering department. we have real work to do.
  • "WCDMA has changed 240 times in the last two years, due to both technological and political factors,"

    Good Christ! That's nearly as many times as Redhat has changed their direcory structure! :p

  • This kind of technology (using software in the RF stage) would appear to make ham radio appealing to those with the same inventive spirit that brought a lot of innovation to radio technology.

    One thing that made Amateur Radio appealing to a lot of the old timers was the fact that they could build their own transmitters and receivers and antennas. With Software Defined Radio Systems, hams could build their own antennas and code their own radios.

    Code could be shared among enthusiasts that worked particularly well for particular applications... Hard core hams could overclock their systems to run serious number crunching code for enhanced dynamic range to pull out weak signals, etc.


    KF8QE

    • This is already happening to a certain extent. AMSAT has a PSK demodulator that is implemented with a programmable DSP. Many of the experimental digital modes on HF use a PC with a sound card and the appropriate software to demodulate the audio from the transceiver. DSPs have become popular for audio filtering and processing, like the boxes that will automatically notch out unmodulated carriers from the audio in a SSB receiver.

      The trick would be to design a reasonably priced receiver that fed the IF into an ADC, allowing a microprocessor to do IF filtering, demodulation etc.

    • Except that they don't. The vast majority of hams, if they even acknowledge the existence of such technology, are content to let a tiny minority innovate while they merely consume.

      The fact that this stuff is viewed as significant (it is far from new) merely shows how badly out of touch most hams are with anything resembling modern technology.

      Grumble!

      ...a ham
    • Well, I am not directly involved with SDR tech yet in ham radio, but I understand the tech, and when I have the time, I will get involved. Anyway, here is the link: http://www.tapr.org/sdr/ [tapr.org]

      So, any hams that want to get involved, there is a start, I know I will be some time in the next 12 months, I'm really hanging out for a HF version, or maybe even a 6m one, maybe I should design one...

      VK3TST

  • I have been wondering about technology like this for a while. More specifically, the possibility to build cellular stations that are compatable with every communications protocol. If a company could build small communication units that were completely reprogrammable, they could place them around cities and open lease agreements with various phone and communication companies.

    I'm not familiar enough with FCC regulations to know that someone could actually build a business model around this, but the idea still intrigues me. We're going to be using radio based gadgets for the foreseeable future, and a company that could move itself to become an all purpose wireless provider would have a good deal of potential.

    • Re:Cell phones (Score:2, Insightful)

      by mellifluous ( 249700 )
      It is technically feasible, but also a major headache. There would also be some serious economic considerations. Here are some obstacles such a technology would have to overcome:

      1) Making the cost/benefit ratio of the processing power required for software radio competitive with a single-technology solution.

      2) Ease of integration into different infrastructures. Just because you can make the air interface work with any type of radio technology does not mean that you've fixed the whole problem. Every layer of the OSI model must be satisfied.

      3) Regulatory requirements. Such a device would have to demonstrate compliance with a wider range of standards (both government and industry-enforced) than normal. This could make time to market longer and more expensive than a simpler product.

      I'm not saying that this shouldn't be pursued, but given the current state of affairs I would be surprised if someone could make it profitable.
    • If you build such base stations and sell them, there goes your hardware business. In my company (GSM cell phone base stations) we are JUST starting to sell software as a separate product..as in last year for the first time. Before that all sales were hardware.
  • Motorola was working on a chipset for the cell phone market that was highly programmable - it could simulate differing standards on the fly. What killed the project was horrible battery drain - hopefull these people have figgured it out.
  • ...is that when people start talking about everything playing well with other devices there is a problem.

    It could even function as an FRS (family radio service) walkie-talkie, listen in on your baby monitor, and act as a garage-door opener.

    I am of the opinion that if I can monitor my baby and open my garage door, so can someone else. And with the lack of security that most people tend to apply to their equipment I do not like this idea at all.
  • Swap mp3's while driving down the freeway.
    What could be better?
  • The first big application for this was cellular base stations for AMPS, the first big cellular technology. AMPS is narrowband FM analog voice, with up to 800 channels in a cell site. Early implementations required one physical tranceiver per channel, which was expensive and bulky, even though they were packaged as rackmount boards with lots of shielding covers.


    The digital implementation sucks up the whole cellular band, downconverts it to a traditional IF with an oscillator and mixer, applies IF filters, and then digitizes the result. A DSP system then simulates all the receivers simultaneously.
    (FFT the whole band once, then read out the value for each channel.) The trick is having enough compute power.

  • The [gnu.org]
    GNU Radio project is doing stuff like this. There's some pretty neat code already developed, using cheap A/D converters and varactor tuners from old TV sets. Cool stuff.
  • why we all think software-defined radios are cool but software-defined modems are crap?
    • Most modern modems are "software defined". The modem is implemented as software for a general purpose programmable DSP. The "winmodems" just use your system's CPU to replace the DSP on the modem board. The problem with a winmodem is that it replaces a $5 DSP on the modem board with a $200 CPU on your motherboard.
    • Because a propper SDR would have a dedicated processor, and that is why software defined modems are crap, if they used an internal processor, and DSP, software modems might actually be good!

      VK3TST
  • SDR can implement the old protocols but not the new ones.

    It takes complicated signal structures and protocols to pack the most information into the least bandwidth. With bandwidth getting more expensive in the FCC auctions, wireless service providers require the most effective (and complex) protocols. Basically they implement what the technology supports after very careful study...$Billions ride on getting the choice right. The most cost effective designs use bleeding edge custom ASIC's.

    The performance available from custom chips far exceeds what someone can implement in a DSP or general purpose processor (or even an FPGA).

    Sure you can wait 5-10 years and software will catch up. But by then, the wireless operators will have upgraded to a new protocol that software can't do.
  • And I agree with several of the posters - I'd like to see this sort of thing work its way into a box next to the computer.

    Take [intersil.com]
    this bad boy, a four channel programmable down converter - 4 radios on a chip. You feed in 1 to 4 IF data streams, and this guy will decode them - about 2 billion operations per second, on a chip the size of your thumbnail (micro-ball-grid array). I work with its little brother, the 50214, on [p25.com]
    my project, and I can't wait until I get past the big stuff and get some time to play.

    That's the sick thing about soft radios: you do one down conversion from RF to IF, then digitize it, and from there on it's all math. When you are a ham operator, a math geek, and a software engineer, and you get paid to play with these, well, life is good.
    • Wowbagger,
      I'd really like to hear more about your project and get your opinion of an idea of mine as well. Please drop me a line at none_yobidness (at) hotmail dot com.

      Thanks!
      • Well, as far as telling you more about my project... I'd feel very uncomforable going into any greater detail than the marketing data I pointed to in the main post - there are issues of disclosure.

        As for hearing about your idea - same thing. If your idea is close to something we are already working on, then it opens up a huge can of worms. If your idea ISN'T something we are working on, but pertains to what we do, then it's not just a can, it's a barrel.

        Basically, if you don't feel comfortable detailing it in a post to Slashdot, then I don't feel comfortable discussing it without running past Legal. Sucks, but that's life in the twenty-first century.
        • I understand. I dislike that it has to be that way, but I understand. It's not that I want to turn my idea into a commercial product - in fact, I'd rather it be an 'open hardware' project. The only reason I'd hesitate to describe it here is so that it doesn't get patented out from under me (the concept of 'Prior Art' is dead) which would preclude it from being 'open hardware.'

          I appreciate your reply, and good luck with your project!
          • I would disagree with your statement that "prior art is dead" - the biggest issue is to make sure that your prior art is well established and incontrivertable. The best thing would be to start a section on a high profile location, like your journal here or on Sourceforge, as well as trying to get a story in an appropriate trade journal.

            Since we are talking about software radio, I'd suggest writing up your idea, and submitting it to QST (http://www.arrl.org). ANYBODY in the radio profession will read QST (and QEX), and that makes it very hard for a would-be patent scum to say "I didn't see that!".

            I'm glad you took my response correctly - I was afraid you'd think I was blowing you off, rather than covering my own ass. If I owned the company, it might be different (hence why if I ever did strike out on my own, I would avoid letting my company become publicly traded: as soon as you become publicly traded, you no longer own the company.).

            • Ah, a fellow ham! I subscribe to both QST and QEX. I would love to publish the project, but I'm a little over my head as far as the 'state of the art' in digital radio design. I've been looking at the Analog Devices chips, which seem very powerful, but I don't know enough about DSP and such to get a working prototype going.

              Maybe your company would like to sponsor the project in return for commercial rights (as long as experimenters can still make their own version) and recognition in the article? 8-)

  • Software Defined Radios are going to change the radio world (the two-way radio world at least) in dramatic ways. They open up the possibility of completely getting rid of the "real estate" approach to spectrum allocation.


    It's still very expensive to do a true SDR that can suck in DC to daylight (or any reasonable subset thereof) and digitize it. However, you can take beginning steps by using traditional methods for the "front end" of the radio, and using DSP techniques at the back end. Hams are doing that now, and we're seeing some very interesting results.


    Bob Larkin, W7PUA, developed a DSP radio called the DSP-10 that works at the ham 2M (144-148MHz) band, with a DSP board that's essentially a souped-up sound card. In addition to handling normal communication modes, Bob programmed the DSP for several unique modes that involve extremely narrow bandwidths (easy for DSP, virtually impossible to do in analog) and very long data integration times.


    The result is that a pair of these radios were able to talk to each other via "moonbounce" (yes, bouncing signals off the moon) with power levels and antennas far below the macho amplifiers and antennas normally required.


    The DSP-10 software is fully open source, so it's wide open for experimenters to work with. The radio itself is being sold as a kit by TAPR (http://www.tapr.org) [tapr.org], a ham radio R&D organization. Details on the DSP-10 are at http://www.tapr.org/tapr/html/Fdsp10.html [tapr.org].

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