Microsoft Sniffs Out Unused Wireless Spectrum

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."

Comments

Isn't this contradictory?

[RightSaidFred99]

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.

Re:Isn't this contradictory?

[Z00L00K]

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.

Re:Isn't this contradictory?

[Richard_at_work]

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.

Re:Isn't this contradictory?

[Sir_Sri]

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 see a lot of problems with this system, but in a low powered device the harm it could do is hopefully minimal.

Overall it's a good idea, and a useful research project. But it requires the government to manage its use, and well, depending on the party in power (and this applies everywhere, not just he US) the idea of more government controlling what your devices can and cannot do might offend people.

Re:Isn't this contradictory?

[postbigbang]

No, no, and no.

1) you're not going reduce the demand for bandwidth, just like you're not going to make taxes go down, for long.

2) the whole point of wireless is mobility, not fixed point-to-point multicasting. The 802.11a/b/g/n frequency allocation sucks, although the a/n that uses 5Ghz has more non-interfering channel allocations. But density is not in your favor no matter what wise-ass antenna you try to use. There's leakage and uncontrollable other-device-location that will always thwart your design. Some over come this, but it's an endpoint problem that's really not covered at all by this misadventure that Microsoft is embarking on, and

3) You have no clue what it takes to do rural broadband, nor the problems of how twisted pair networking operates, over what kind of distances, and to what degree of external signal problems.

Go fish.

Re:Isn't this contradictory?

[postbigbang]

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, ship-to-shore, and other services that you shouldn't fool with or inadvertently jam.

Overall, I think Microsoft can find what it needs by polling with a spectrum analyzer, rather than have a bunch of people think they're doing something useful like SETI.

Re:Isn't this contradictory?

[zach_the_lizard]

Cat6 has a maximum length of 100m (330 feet or so) for 1Gb Ethernet and below; faster speeds get less. Are you sure wiring rural areas with that is going to be cheap? You'll need more than just better cables; IIRC the distance comes from the travel time for a signal, and after 100m the latency is such that two stations will transmit at the same time, not knowing the other one is transmitting. So you'll need a switch or certain hubs (Class 2?) roughly every 100m.

There are plenty of areas with more than 100m of distance between houses, let alone the CO. 1 mile would be about 1600m, so if you must have cat6, that'd be 16 100m segments. Maybe add another 1 or 2 to account for patch panels, slack in cables, etc. That'd suck a lot.

Re:Isn't this contradictory?

[postbigbang]

There's a lot of dark fiber out there.

But wiring it up IS a problem. You need poles, easements, contractors, and terminations. None of it's cheap. And fiber is a great solution if you can afford it. Some people have used Hughes sat dishes, which work ok if you don't mind the latency and cost.

You need people to fix it after bad weather, that have pretty expensive rolling costs, like training, trucks, TDRs, repair gear, and you have to pay them, their insurance, and so on. It's not a trivial endeavor.

We need something like the REA for other utilities, like broadband, etc. Then there's the backhaul/interconnect. You could help get it subsidized, but then we're back to who can we afford to subsidize, and to what cost? The rural poor are especially left behind.

Re:Isn't this contradictory?

[jd]

There is, as other posters have noted, plenty of dark fibre. Communities, ESPECIALLY rural ones (and my mother's side comes from North Dakota, so I know how rural things get), have a central point. They're not randomly dotted around.

Option 1: For a close community, you find a central point and run a tap from the nearest dark fibre to that point. That gives you a rural hub to run from.
Option 2: You run a ring of fibre round the community, again running a tap from the nearest pre-existing dark, with branches as necessary. Use a curve-fitting algorithm for different groups of locations. You'll end up with everything inside CAT6 range.
Option 3: For simple street-based communities, run fibre along the street and have a switch convert to CAT6 every N houses the way cable does.

Where new fibre is being run in areas (such as North Dakota) where temperatures can vary wildly, either run the lines about 5-6 inches below the ground (where temperatures will remain essentially constant) or jacket the damn thing.

Re:Isn't this contradictory?

[jd]

I've probably lived in more rural communities in more countries than you could shake a stick at, so cut the wise-ass remarks. If I say I know damn well that you can get CAT6 to people's houses, then I suggest you start by asking how, not telling me that it can't be done. I won't say the problem's not solvable unless I've actually done the work to know it is solvable and have the engineering skills to know what the limits of theory are in practice. The people who get things done are not the ones who say it can't be done. The ones who get things done are the ones who establish IF, WHEN and HOW -- questions you utterly fail to ask.

If you haven't asked those questions for each and every damn article you read and each and every post you reply to, you have failed.

Re:Isn't this contradictory?

[RoFLKOPTr]

I've probably lived in more rural communities in more countries than you could shake a stick at, so cut the wise-ass remarks. If I say I know damn well that you can get CAT6 to people's houses, then I suggest you start by asking how, not telling me that it can't be done. I won't say the problem's not solvable unless I've actually done the work to know it is solvable and have the engineering skills to know what the limits of theory are in practice. The people who get things done are not the ones who say it can't be done. The ones who get things done are the ones who establish IF, WHEN and HOW -- questions you utterly fail to ask.

If you haven't asked those questions for each and every damn article you read and each and every post you reply to, you have failed.

Why the shit would you run Cat6 rather than fiber? Cat6 is only good for 100 meters, it's not capable of anything close to the capacity of fiber, and it's susceptible to electromagnetic interference. The fact that you're suggesting running Cat6 to every home in a rural area shows that you have no idea what you're talking about.

Re:Isn't this contradictory?

[postbigbang]

At lower data rates, Cat6 is good for longer distances, but I also disagree that it makes a good choice. Even shielded twisted pairs just aren't good for rural distances. This is the reason why DSL doesn't go far from a central office: the signal degrades.

Re:Isn't this contradictory?

[postbigbang]

No.

If you ran Cat6 to a rural home than you made an expensive and WRONG choice at best, and used a hammer where a screwdriver should go. TSB-67 cable isn't designed for rural home runs at all; if you got any kind of data rate, it was through luck, not design.

I, too, get things done, and with a great deal of experience running an enormous variety of installations, I don't believe you. If you have the how, then why are you using the wrong stuff for long end runs?

Re:Isn't this contradictory?

[Stickybombs]

5-6 inches? I hope you meant feet. The frost depth in southern Michigan is 42 inches. I'd imagine ND could be even deeper than that.

Re:Isn't this contradictory?

[postbigbang]

I'm really familiar with business and rural broadband systems design. You'll have to trust me on that. Fiber is the best solution for the long run; it's better to terminate it and route indoors to a home cable plant of some kind.... call it a rural IDF.

Somewhere there's a communication breakdown; if on my part, I apologize. I've seen utilities try IP over utility wires in various configurations, modulated twisted pairs, point-to-point hybrid systems involving elaborate towers and pringles cans, and much other strangeness. Were I to recommend to Congress what to do, it would involve fiber to the home each and every time, and make the transport open to any reasonable provider as a service, as is done in a few progressive installations/sites/geographies.

Fiber is easier than ever to install, aerially, buried, across ponds, lakes and rivers, and alongside much other stuff. It's my preference, save that Corning wants to dominate the world with its fiber offerings.

No, not rocket science, but it has its own politic.

Re:Isn't this contradictory?

[postbigbang]

The fiber routers really aren't that expensive, and if you're sensitive, converting fiber to copper isn't that expensive, either. If you're going to go thru the expense, you might as well do it right unless geography and nearby drops are in your favor. Fiber terminations aren't that much more expensive than copper, and deliver long term viability that's hard to beat. If budget's a problem, then your up-thread spanning-tree suggestion is viable.

Ask the people in Loma Linda CA about what it's like to have FTTH; most don't care because they have two Cat6 jacks in every living space provided by a router in the upstairs master bedroom of all new construction in most of the past decade. Yes, the LL installation is close-in, has an IDF in each housing addition. But the principal is the same, and the retrofit isn't that much more expensive even given long runs-- no repeaters are necessary and fiber jackets are pretty bullet-proof and even spliceable these days.

Re:Isn't this contradictory?

[kullnd]

"upwards of $8000 a throw" --- Ok, and they can also be had much, much cheaper... It is not as though we are going to be putting enterprise datacenter equipment inside of a house for internet. Even if the rural home had to buy the $1000 router with fiber capabilities so that they could plug into the fiber internet run into their house, I'm pretty sure that many of those residents would be more than willing to front that cost for some decent internet. (Not like those dishes referred to earlier are cheap, and they suck!)

Snore

[dtmos]

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).

Reminds me of the static IP address days

[$RANDOMLUSER]

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?

Re:Wouldn't be necessary with spread spectrum

[Sarten-X]

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

[hazydave]

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.

It's being done already!

[Cyberax]

It's being done already, in other countries

My house is connected to 3 Internet providers. Each provider has a fiber-optic trunk line, mediaconverter and a switch with Cat5 wiring connecting individual flats to it.

Such providers are historically called "local local networks" (heh, almost like "ATM machines") here because they started appearing in late 90-s and early 2000-s when Internet connectivity was EXPENSIVE here, like 20 cents per _megabyte_ expensive. So operators of these networks provided 'local' resources for filesharing, game servers, forums, etc. Traffic to these local resources was either very cheap or completely free.

Oh, and I live in Ukraine.

So, wiring up everybody is possible. It's not that expensive because it was possible to do in a poor country 10 years ago. With much cheaper equipment it's even more possible now.

Re:Nobody cares about Scam Radio

[CamoCoatJoe]

Okay, I'll bite. It's been a while since I've wasted time arguing on Slashdot.

Ham Radio is just a big scam so that a bunch of Republican retirees can sit around with ancient equipment and chat with their buddies without having to pay for phone time or internet access.

'Cause ham radio equipment is so much cheaper than the phones that they already have, and that they still use? Of the few hams I know, they all have phones, most of them including cell phones.

They do nothing that cannot be done better by actual professional crews

Some hams are also radio professionals. One ham I met was also a (cell phone?) network tech, who became a ham operator because he wanted to learn more about the fundamentals of radio technology. Being a ham makes him a better member of his "professional crew".

and they do nothing in the research arena anymore.

You mean like making the first cell phones? CDMA was made and used by hams before anyone else. How exactly would an inventor experiment with a new radio tech idea? Auction for bandwidth just to find out if your idea even works? Ask permission to innovate? Yeah, that's American.

In 20 years nobody will know or care what a ham radio is. The world will be a better place for it.

Yeah, a lack of fault-tolerant, long range, emergency radio links will surely make this world a better place. If you figure letting polluting humans just die instead of coordinating rescue efforts is a net gain.

Ham radio is about freedom, something a few of us still care about, not just cool new cell phones. The freedom to transmit using any protocol, any modulation, to anyone, anywhere. For all the talk about the internet being a tool for free speech, it isn't nearly as free as ham radio. Hams have gotten information across borders in some of the countries cracking down on protesters, when the internet lines were completely cut off, and people were being searched for media at the border. They've got ATV to get video out of there. What do you have?