Catch up on stories from the past week (and beyond) at the Slashdot story archive


Forgot your password?
What's the story with these ads on Slashdot? Check out our new blog post to find out. ×
Microsoft Wireless Networking

Microsoft Sniffs Out Unused Wireless Spectrum 102

alphadogg writes "Microsoft researchers have designed a scheme for measuring whether licensed radio frequencies are actually being used so unlicensed devices can use it, something that may become necessary as demand for wireless applications grows. The architecture, called SpecNet, would sense and map where spectrum is being used and more particularly where it's not — so-called white spaces, according to a paper being presented next week at the USENIX Symposium on Networked Systems Design and Implementation in Cambridge, Mass."
This discussion has been archived. No new comments can be posted.

Microsoft Sniffs Out Unused Wireless Spectrum

Comments Filter:
  • If you're using licensed spectrum, you must be licensed. So your "unlicensed" device must be licensed to use the licensed spectrum. It's not like the FCC's going to be like "Oh, well you are not licensed to use spectrum xx.x, but if nobody else is then what the hell, go ahead!". So really this is a licensed device that can optionally use unlicensed spectrum.
    • by Z00L00K (682162) on Sunday March 27, 2011 @02:47PM (#35631534) Homepage

      I can agree that it can cause quite a racket if the FCC ever gets a report of abused radio spectrum.

      And what looks like unused may not be unused at all but can actually be used for measurements, alarm systems or even remote detonations so you can't tell that it's unused by sniffing it.

      Something like the parking spot right outside your window that's empty when you are at home - that actually is used when you are at work by the maintenance company that happens to have an office in the building you live in.

    • In quite a few places you can use a licensed spectrum legally without a license if your use is low powered and does not cause issue with a licensed device - if it does, the licensed device or user has the onus and can shut you down.
    • by Anonymous Coward

      Yea, this isn't a technical problem. It's a legislative one. Meaning: forget thinking about it unless you have a few spare millions to bribe politicians.

    • by Sir_Sri (199544)

      Imagine for a minute you could build a generically unlicenced device, which shouldn't interfere with licenced ones. So it works on unlicenced space (or on licenced space but it can't find a free channel), now you have two choices, either the device can fail to operate, since there are too many devices. Or it can automatically go hunting for new channel space.

      Ideally a device should be able to hunt around for free wireless spectrum, and then resolve if it can stay there when something else shows up. I can

      • This connotes that both sender and receiver know when channels switch. In Bluetooth, there's frequency hopping that allows this, albeit at really low power. But if your device is at one channel, and must suddenly shift away, then sender and receiver must know what they are, otherwise you're a broadcaster. Low power broadcast is ok, within certain bounds in the US, given certain spectra.

        When the low power device interferes with something in a licensed band, it could be critical equipment, public safety, FAA,

    • Well I may not be understanding this right but that would basically just be a issue of firmware. I know I unlocked more channels for my wireless router by installing FOSS firmware on it and if using unlicensed channels became legal all you would have to do is update firmware for existing devices.

    • by Anonymous Coward

      In traditional /. fashion, I didn't RTFA, but I did see a MS researcher give an eerily similar sounding presentation a couple months ago. He discussed an algorithm to detect users on the 700 MHz spectrum. This is a "licensed" spectrum, but has been opened up by the FCC for unlicensed use on unoccupied channels. A major issue was determining which channels were not being used, and how to adaptively change when a licensed user starting using the channel. They discussed proposing a protocol to the FCC specific

  • Snore (Score:4, Informative)

    by dtmos (447842) * on Sunday March 27, 2011 @02:51PM (#35631554)

    Microsoft has been in this space for years. They, for example, contributed to the original FCC TV white space trials in 2008 [] (see the February and March entries).

  • by Anonymous Coward
    Nothing found at L1, lets use this free spectrum for WiFi.
  • by $RANDOMLUSER (804576) on Sunday March 27, 2011 @03:06PM (#35631652)
    Remember assigning static IP addresses by the seat of your pants? Pull a number, X, between 2 and 253 out of your ass, ping 192.168.254.X, if nobody answered, go ahead and assign your new network printer to it. Hey, what could go wrong?
    • Ah, I remember that as a tech back at my high school. Only problem is, we had more than 254 computers, so we would be continuously knocking computers off the network. But it was OK, because it was almost never the same people. Then Netware would break, and things got interesting.

      Eventually we figured out that we could assign the lab computers to a subnet. Implementing this took some fighting becase "it worked well enough".

      Glad to be done with that...

      • by Bios_Hakr (68586)

        If you had a single class-c, wouldn't subnetting make it worse?

        A /24 has 254 usable IPs. A /25 only has 252 usable. For every subnet bit you set, you lose more and more usable IP space.

        With that being said, subnetting (especially CIDR) is an invaluable tool. It breaks my heart that a lot of our newer network engineers just can't do it. They learned it to pass the CCNA and then went back to using CIDR calculators.

        • Can't say I'm a network engineer, so subnet may be the wrong term. We were all behind a NAT, so we just made a new /24

          • by Bios_Hakr (68586)

            No problem. Yeah, NAT is the way to go for most networks.

            If you have a large network, you can do a and then subnet/VLAN that down.

        • by kullnd (760403)
          I would agree with you if anyone calls themselves a network engineer (or even network administrator) they should be able to figure out CIDR without a tool, but you bet I use a calculator! Are you suggesting that I should pull out a piece of paper and write a bunch of ones and zeros when I can just pull up the CIDR app on my phone and be done with it? I subscribe to the "work smarter not harder" idea, which includes the use of tools I have available to make my life easier... And no, I am not a "newer net
        • by bryan1945 (301828)

          "They learned it to pass the CCNA and then went back to using CIDR calculators."

          Just like I had to learn the capitals of the 50 states, then went back to looking it up when I needed to. No, I'm not a network engineer nor a CCNA; did have to do some network subnetting once in a (rare) while. There is a reason we human-like beings build tools- to make make stuff easier and quicker. But if you're happy memorizing stuff a program can do just as well, more power to you (seriously- I have respect for anyone th

      • by cthulhu11 (842924)
        How friggin big was your high school that it had more than 254 computers??
        • Well, it was a high school and a middle school, separated by a block or two. They actually had a pretty decent 10 megabit (or so) microwave link set up between the schools, because they could only afford a T1 at the one and centralizing the network made sense (I guess?)

          In any case, the middle school had 5 computers or so per classroom (to facilitate group projects), the library had about two dozen, and all the offices and other rooms had a few each. Probably about the same in the high school, except each te

          • by cthulhu11 (842924)
            Wow. My high school had five computers -- Apple ]['s. Four in the physics classroom where the asshole teacher only let them be used once a year, and one in a math classroom where the hoods camped on it playing games. Oh, yeah the attached Vo-Tech had an IBM 360 that a former teacher had run FORTRAN card jobs on.
            • Uh, this was about 6 years ago. But the computers might as well have been Apple ][s. To their credit, they weren't wasting money - the computer labs and library got the new computers on about a 3-year cycle (30 new computers a year or so), and the rest got 'trickled down' through the district on a need-based system - labs in the high school and the HS library got them first, those newish machines went to the teachers in the high school, and their only-slightly older machines went to the middle school and el

    • by bledri (1283728)

      Remember assigning static IP addresses by the seat of your pants? Pull a number, X, between 2 and 253 out of your ass, ping 192.168.254.X, if nobody answered, go ahead and assign your new network printer to it. Hey, what could go wrong?

      Actually, the practice is getting standardized: ZeroConf []

  • Did you say "SenseNet"? I don't see how could *that* could go wrong...
  • Interesting. When they were creating the white space spec. MS (and others) said there was no way to create a device like this. Guess now they want one, it's easy, lol
  • If this will really be attempted, operators of emergency radio systems and HAM radio operators are going to collect a bucketful of fines!
  • "One major hurdle to clear: the cost of the analyzers, which go for $10,000 to $40,000 each. " I guess they haven't seen the RF cochlea []. That could be developed into something that could be included in every mobile RF device.
    • by artor3 (1344997)

      That's a really interesting design, thanks for posting it. However, from their paper [] (paywall) it seems like the RBW (to use the spectrum analyzer term) is dependent on how many of these filters you put in. If you want a fine resolution over a wide band, you're going to need hundreds of these things per decade, and thousands overall. Certainly possible, and I wouldn't be surprised to start seeing them before long, but maybe not that much cheaper than conventional spec ans -- remember, a lot of that $10k

    • See US patent 6,768,398 [], filed 12 December 2001. The RF cochlea is a relatively old idea.

  • This is BS (Score:4, Informative)

    by hazydave (96747) on Sunday March 27, 2011 @04:30PM (#35632100)

    The Microsoft thing is BS.. not the idea in general.

    The whole FCC idea of "Whitespace" is that we have a huge chunk of the best overall spectrum put aside for OTA television. But in most areas, most of that spectrum isn't used.. even given the losses due to original cellular (channels up to 83) and the more recent 700MHz auction for 4G (channels in the 60's on UHF).

    So the idea of whitespace radio is simple: treat it as ISM radio (like 900MHz and 2.4GHz in the USA) once you acertain that the channel (in 6MHz chunks, just like TV, in the USA) is not used.

    The problem is, just using sensing, you can't know if the channel you pick is clear. Your receiver can go into spectrum analyzer mode and not see a thing, but it's still very possible your transmitter is going to interfere with the guy down the street. who for whatever reason (rooftop antenna with 40dB LNA) can actually get that OTA channel.

    Thus, the current plan for whitespace radiio... radios need to be location aware, and only use channels legal for that specific location. This is trivial to do, and it pretty much just works. Nothing MS is doing here improves this, far as I can tell. You can't be correct about the usability of a channel from a single monitoring point, whether you spend $100 or $100,000 on that spectrum analyzer. And so, given the need for one node in the network to have a separate internet connection, nothing MS does online is an improvement over the basic idea -- we absolutely know where the licensed radio is, because it's LICENSED! That license is for a certain areas, and no army of MS spectrum analyzers can be certain that your neighbor can't receive that channel, within the licensed area. Beyond that area, it just doesn't matter -- you get to use that channel anyway.

  • Until the device goes "Oh look, nobody's using this, I'll grab it" and it happens to be an emergency frequency that HAS to be kept clean for, well, emergencies.

    I dunno about your country, but in mine you better have a DAMN GOOD reason to use certain frequencies that are "unused"...

    • I'm pretty sure that if such a device was approved by the FCC it would be programmed to avoid using emergency frequencies.

  • Wasn't Google doing this a few years ago and own a patent or two on it?
    If I recal correctly, the FCC disallowed this technology to be used in the upcoming Google phones.

Related Links Top of the: day, week, month.

panic: kernel trap (ignored)