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Software Defined Radio Systems

Posted by timothy on 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."

11 of 60 comments (clear)

  1. If only I could get a USB version.... by squeegee-me · · Score: 2, Insightful

    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.

    --
    Who wants Pork Chops?
  2. Changing Standards by trcooper · · Score: 2
    "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

  3. Cell phones by bartle · · Score: 2

    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.

    1. Re:Cell phones by mellifluous · · Score: 2, Insightful

      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.

  4. Re:ObNotNew by color+of+static · · Score: 2

    It's been around longer then three years. I remember seeing COTS components to do just this in the early 90's. Between being able to sample an entire IF, and use wide band mixers with software controlled Direct Digital Synthesis (DDS) you can almost make an entire radio software defined, front and back end.
    Your exactly right about costs. It's cheap and easy to make a simple radio that recieves a narrow band, and has a simple decoder. Adding total flexibility means you have a similiar component count, but instead of 10 for a penny they cost 1 for $10.

  5. Re:a new wave of techno-hams? by Detritus · · Score: 2
    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.

    --
    Mea navis aericumbens anguillis abundat
  6. This has been around for a while by Animats · · Score: 2
    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.

  7. Re:SDF Stuff by Gordonjcp · · Score: 2

    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.

  8. Re:Could someone explain... by Detritus · · Score: 2

    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.

    --
    Mea navis aericumbens anguillis abundat
  9. I work with this stuff every day... by wowbagger · · Score: 2

    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
    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
    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.

    --
    www.eFax.com are spammers
  10. Re:SDF Stuff by Gordonjcp · · Score: 2

    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.