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."
Snore (Score:4, Informative)
Microsoft has been in this space for years. They, for example, contributed to the original FCC TV white space trials in 2008 [fcc.gov] (see the February and March entries).
Re:Wouldn't be necessary with spread spectrum (Score:4, Informative)
You're kidding, right? Instead of simply allocating the spectrum based on frequency, we have to allocate by frequency and time, synchronize all relevant devices, and build every device with proper radio hardware to switch frequencies rapidly. Maybe it's a small price to pay for the increased security of such a transmission... until the CIA/NSA/Illuminati/tinfoil-hat-enemy-of-the-week gets their hands on a single receiver, and they know the psuedorandom sequences involved anyway.
Most spread spectrum algorithms improve resistance to accidental interference, because they simply provide a "moving target". If two spread-spectrum devices are transmitting simultaneously, they will seldom interfere with each other during normal operation. If the interference is intentional, no amount of hopping or alteration will stop it for long, because the interfering transmitter can be designed to follow the same pattern, or simply broadcast on all frequencies the device will use.
This is BS (Score:4, Informative)
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.