Beta
×

Welcome to the Slashdot Beta site -- learn more here. Use the link in the footer or click here to return to the Classic version of Slashdot.

Thank you!

Before you choose to head back to the Classic look of the site, we'd appreciate it if you share your thoughts on the Beta; your feedback is what drives our ongoing development.

Beta is different and we value you taking the time to try it out. Please take a look at the changes we've made in Beta and  learn more about it. Thanks for reading, and for making the site better!

First Public White-Space Network Is Alive

timothy posted about 5 years ago | from the ubiquity-keeps-getting-bigger dept.

Networking 97

An anonymous reader writes "The first public white space network officially launched on Wednesday in Claudville, Virginia. It uses sensing technology from Spectrum Bridge with software and Web cams supplied by Microsoft and PCs from by Dell. The project was funded the TDF Foundation. White space networks use unlicensed television spectrum and have been called 'WiFi on steroids.' They offer more bandwidth, over larger areas, than does WiFi. IT companies duked it out with broadcasters for years to get white spaces approved by the FCC. They finally got the FCC's nod in November, 2008."

Sorry! There are no comments related to the filter you selected.

"Stud Dogs" troll wanted (-1, Offtopic)

Anonymous Coward | about 5 years ago | (#29829531)

Somebody please post the "stud dogs" troll!

Good thing (1)

Cryacin (657549) | about 5 years ago | (#29829575)

Thank god it didn't go to the cell companies.

Re:Good thing (1)

icebike (68054) | about 5 years ago | (#29829699)

It should have.

The frequency range is far more suited to cell service than the current ranges, it has better building penetration and greater range.

Cell is what the people want. The ridiculous prices we pay for cell service is in part due to the shortage of bandwidth. (And before you jump on the obscene profits bandwagon, go read a few 10Ks of cell companies. Its not all that rosy in profit land).

Public WIFI will simply once again prove the Tragedy of the Commons, as if we haven't learned that enough times over the course of history.

Re:Good thing (2, Insightful)

perlchild (582235) | about 5 years ago | (#29829787)

Anything will prove "The tragedy of the commons" as it doesn't really need proof at this point. However, expanding the commons is like that. The alternative is a shrinking commons, or actually having enough accountability and imputability that it's not really "the commons" anymore, but some form of public property under private ownership or management. I for one welcome expanding commons.

As for cell bandwidth, the process is so political, it's not really surprising they refuse or fight less for frequencies that are better, and duke it out with google for poorer frequencies. It lets the management say it's all someone else's fault.

Re:Good thing (1)

node 3 (115640) | about 5 years ago | (#29832013)

Anything will prove "The tragedy of the commons" as it doesn't really need proof at this point. However, expanding the commons is like that. The alternative is a shrinking commons, or actually having enough accountability and imputability that it's not really "the commons" anymore, but some form of public property under private ownership or management. I for one welcome expanding commons.

Or, the commons can be managed, as commons are all over the world, and all throughout the US, even though it seems it's the Americans who seem all too quick to forget this fact when the topic of the "tragedy of the commons" arises.

They can be managed by the government. It works with parks, and beaches, and waterways, skies, roads...

So, with this spectrum, just have the government provide a set of rules that favors wide adoption of individual citizens, while keeping a few people from ruining it for everyone else. This happens with WiFi by limiting the broadcast strength. With the White-Space spectrum, different rules will make sense, as it naturally affects a wider area.

This seems so fundamental, I can't fathom how people always seem to miss this.

Re:Good thing (1)

TheRaven64 (641858) | about 5 years ago | (#29833299)

Exactly. Remember old style Ethernet? It was another example of commons; there was a single bus, and only one computer could be transmitting on it at a time. And yet, somehow, it worked well when lots of computers were all trying to use it at once (well, within the limits of the total available bandwidth). How did it work? By using the same (very primitive) algorithm for allocating space on all of the clients.

There's no reason why this same model couldn't be used for public airspace; anyone can use it as long as they use a mandated data link layer protocol. If everyone is using it, then you will not get much bandwidth each, but in that case there is a strong incentive for the people with other alternatives (e.g. a wired network or proximity to WiFi) to switch to using that, which frees up spectrum for everyone else. If you're caught using the wrong protocol then you are subject to the same penalties as using any other unlicensed transmitter.

I would probably implement this by allocating various parts of the available spectrum to different protocols on a ten year rolling program, with one part coming up for review every two years. That way you can keep rolling out new protocols as the technology improves, but anything you deploy will keep working for several years.

Re:Good thing (1)

queazocotal (915608) | about 5 years ago | (#29837491)

There is unfortunately an absolutely fundamental reason why this is different from ethernet.

Ethernet collision detection works only if you can detect the other side transmiting at the same time as you.

Even neglecting the 'as the same time as you' part - if the interfering transmitter is beyond the range that you can decode the data from it, you can't tell it from the background noise, and you can't avoid transmitting over it.

As an easy to understand and not too misleading analogy.

Consider a sports stadium.

If everyone is talking quietly, everyone can talk to their neighbour without too much difficulty.

If one person wants to talk to someone ten seats away, they can yell - however this disrupts people next to thems quiet conversations.
If everyone wants to talk to someone ten seats away, and tries to do this by yelling, it just results in everyone only being able to hear their neighbour, and sore ears.

Mesh networking doesn't solve this either.

If you replace the yelling by asking your neighbour to pass the message to someone ten seats away along, then there is no immediate overload - but the overall transmission rate drops to 1/10th - as most of the time you're passing messages for neighbours, not youreself.

Re:Good thing (1)

camperdave (969942) | about 5 years ago | (#29830121)

The lower the frequency, the larger the antenna needed to pick up the signal, no? Cell phone users don't want antennas sticking out of their phones, especially ones that are a foot long.

Re:Good thing (3, Insightful)

icebike (68054) | about 5 years ago | (#29830299)

A foot long? Oh come on!!!

We are talking about "700-megahertz" band, covering TV channels 52 to 69 (698 to 806 MHz).

The upper end of this is only marginally longer wavelength than the 850MHz band used for 850-GSM cellular today.

This bandwidth could easily be merged into the cellular spectrum with virtually no change in antenna length required, or at best a marginal increase in length that would easily fit in the modern smart phone package format.

A quarter wave antenna for 850MHz is 3.3 inches.
for 800MHz a length of 3.50 inches is optimal.
for 700MHz 4.01 inches, etc.

The iPhone is 4.25 inches tall. Similar phones have similar sizes, all of which would accommodate a quarter wave for these frequencies.

Re:Good thing (1)

IgnitusBoyone (840214) | about 5 years ago | (#29830745)

I don't know I tend to buy smaller phones. My idea of a perfect phone is a ear peace with voice dial. I am one of the odd balls that tend to like having multiple devices for various things. Ignoring my personal opinions. 4.01 inches is a fairly long antenna and to large to fit in lots of phones. I guess it makes sense for smart phones which need larger bandwidth chunks to be the only phones in this spectrum, but It sure does suck for the few of us that want just a phone and can't get reception due to the 850MHz range.
However, not allowing smart phones to use the 700MHz range isn't going to help my reception either, so no real complaints just looking to post.

Re:Good thing (1)

BarefootClown (267581) | about 5 years ago | (#29835229)

4.01 inches is a fairly long antenna and to large to fit in lots of phones

You realize that antennas don't have to be straight, right? Helical coil is perhaps the most common shape for an antenna....

Re:Good thing (1)

commodore64_love (1445365) | about 5 years ago | (#29837453)

>>>We are talking about "700-megahertz" band, covering TV channels 52 to 69

No we're talking about channels 2 to 51. These devices are unlikely to use VHF, so let's confine that to 14 to 51 which still requires a 9-inch antenna at the lower end... so the grandparent poster was exaggerating but mostly correct when he said "phone users don't want foot-long antennas"

Re:Good thing (1)

Grieviant (1598761) | more than 4 years ago | (#29843205)

I think you're contradicting your earlier post that 700 MHz would be "far more suitable for cell service than the current ranges", icebike. Penetration and propagation losses, as well as more detailed channel characteristics such as fading rate, fade depth, and delay spread, will be very similar at 700 MHz and 850 MHz simply because, as you pointed out above, the relative change in wavelength is small.

There may be something to talk about when comparing 700 MHz to 2 GHz because that's a factor of 3 difference. Despite the improvement in propagation loss, lowering carrier frequency may carry some technology dependent disadvantages as well - e.g. increase in fade duration makes interleaving less effective, less multipath (good for GSM since it's narrowband, bad for CDMA since the RAKE receiver will give you less performance benefit). I'm tempted to say the PCB footprint size would increase marginally, leading to a slightly larger handset, but I'm not 100% confident on that.

Re:Good thing (1)

abarrieris5eV (1659265) | about 5 years ago | (#29830837)

The distinction between "internet", "cell phones", and "tv" gets blurrier every day. People walk around with phones that will save them money by going over voip and wifi when it's available, I haven't own a tv in years, since hulu et al made it not worth the money for cable service. Even when I did have a tv it was hooked up to a mythbox, which relied on internet service for listings. Allowing some parts of the spectrum to be unregulated is a good thing, it allows hobbiests and startups to push the envelope and do things that can't be easily pigeonholed into one of the current categories. If anything we need more unregulated spectrum. 2.4 GHz is incredibly useful for everything from wifi to model airplanes precisely because it isn't regulated. If a large chunk of the 700 MHz band were simply given to miscellaneous digital traffic or something it would be good for a lot of people.

Re:Good thing (1)

Lumpy (12016) | about 5 years ago | (#29830853)

They would not have used it.

AT&T decided that good working 850mhz around here needs to be replaced with the useless 1.2gig crap. I went from 5 bars in the house to 1 in a couple of spots because of their retarded decision. They dont care about better coverage, they care about better profits.. 1.2 gig gives more profit as it carries more services they can overcharge for.
Whitespace would not have had the profit margins they wanted.

Re:Good thing (1)

icebike (68054) | about 5 years ago | (#29830917)

Actually ATT is going in the opposite direction.

They are moving their 3G service down to 850 where ever they have the licenses to do so.

Re:Good thing (4, Interesting)

FooAtWFU (699187) | about 5 years ago | (#29831291)

The last Nobel Prize in economics was basically saying, "Hey, a lot of important 'commons' have a small set of people who use them in repeated interactions, and so you can use game theory principles to describe how these people self-regulate the use of the commons. Oh, and therefore the government getting in on the action is less important than it might otherwise be."

It would be interesting to see whether the use of this spectrum white space "commons" will be effective.

Re:Good thing (1)

Ex-MislTech (557759) | about 5 years ago | (#29831923)

I hear you and understand your point, but I offer this bit of history to remind
you how corrupt, evil, and fraudulent the Telcos can be.

http://www.tispa.org/node/14 [tispa.org]

$200 Billion USD of tax payer money went poof.

We were promised 25 Mbps to all homes in major metros.

What we got was high latency DSL that was slower than a cable modem.

Over a dozen nations with a LOT less money have better broadband than the US.

It is not a issue of money, their hands are DEEP in the public coffers after
their lobbyists greased the right palms.

We have a Kleptocracy, not a Democratic Republic.

It is friggin pathetic !

Re:Good thing (1)

commodore64_love (1445365) | about 5 years ago | (#29837575)

"If you repeat a lie often enough, people will believe it." - I forget the name of the guy but he was correct. The $200 billion didn't go poof. It was used to upgrade noisy analog lines to clean digital & enable 56k in areas that used to have only 19-24k (remember 56k was a big deal in the 1990s). And yes it was used to provide high-speed DSL which I think is a fine service. I pay a mere $15 a month.

Finally: There was NO requirement in the 1996 Congressional bill for fiber-to-the-curb. I've read the bill and it ain't there.

Re:"Stud Dogs" troll wanted (0, Offtopic)

SomeJoel (1061138) | about 5 years ago | (#29829579)

Somebody please post the "stud dogs" troll!

Laziest first post ever.

Re:"Stud Dogs" troll wanted (0)

Cryacin (657549) | about 5 years ago | (#29829659)

Laziest first post ever.

No...

1p!

Re:"Stud Dogs" troll wanted (0, Offtopic)

SomeJoel (1061138) | about 5 years ago | (#29829723)

I'm just saying, as an Anonymous Coward the least he could do is find a copy of said "stud dog" troll and just post the damn thing himself.

Using Television Spectrum (0)

Z34107 (925136) | about 5 years ago | (#29829545)

What channel is Hulu on? v.v

Re:Using Television Spectrum (2, Interesting)

commodore64_love (1445365) | about 5 years ago | (#29836281)

In other news, the residents of Claudville VA are no longer able to watch distant stations in Roanoke due to these internet devices broadcasting over the channels.

The FCC Chairman's comment - "You're not supposed to see out of market stations anyway." One of the local viewers replied, "Now I only get 5 stations from Salem NC, where I used to get 10 from both Salem and Roanoke. They took away my channels."

I welcome any efforts... (2)

ifwm (687373) | about 5 years ago | (#29829561)

I welcome any efforts to improve the woeful state of access in the US. Hopefully, this will lead to more communities exploring the idea of municipal access, something I've always considered the modern evolution of the library.

Awesome (0)

Linktoreality (1487087) | about 5 years ago | (#29829671)

So, how soon until regular IP companies are put out of business, and we get all of our internet from Whitespace?

Re:Awesome (1)

camperdave (969942) | about 5 years ago | (#29829915)

I tried connecting, and apparently I got lots of traffic, but all I got was a blank screen.

Re:Awesome (1)

laederkeps (976361) | about 5 years ago | (#29830245)

Well, if you're surfing the whitespace-powered web using links, what did you expect?

Re:Awesome (1)

GaryOlson (737642) | about 5 years ago | (#29830827)

Did you use the darkspace overlay? Without the darkspace contrast, all the white looks the same.

Re:Awesome (1)

Waffle Iron (339739) | about 5 years ago | (#29830945)

I tried connecting, and apparently I got lots of traffic, but all I got was a blank screen.

I haven't even tried connecting, and I won't be doing so any time soon. I'm not going to buy any equipment for these networks until the big industry players resolve their format war. One camp is trying to standardize on tabs, and the other is pushing for spaces.

White Space (-1, Troll)

Anonymous Coward | about 5 years ago | (#29829673)

How long before the NAACP sues them.

Is this statement misleading? (2, Interesting)

t0qer (230538) | about 5 years ago | (#29829703)

have been called 'WiFi on steroids.' They offer more bandwidth, over larger areas, than does WiFi.

Someone correct me if I'm mistaken, but doesn't lower frequency (30mhz to 300mhz) mean less bandwidth? I could see bonding several channels at once to achieve a higher bandwidth, but doesn't this mostly offer greater range?

Re:Is this statement misleading? (4, Informative)

spottedkangaroo (451692) | about 5 years ago | (#29829775)

It really doesn't matter what frequency when you're talking bandwidth. When you're talking size of the antenna or signal loss the wavelength might matter, but not for bandwidth. The reason you get more bandwidth here is because the spectrum is wider. The ISM spectrum is very very narrow and low power channels all bunched up around 2.4Ghz. With the new white spaces, they can use tons more and much louder. But, yes, they need longer antennas.

As far as the range? You can make a microwave signal go light years and a HAM signal go a few feet (although, there will be some distortion for transmitting a signal over a distance shorter than the wavelength). The range is more of a function of signal power.

Re:Is this statement misleading? (1)

BitZtream (692029) | about 5 years ago | (#29830307)

(although, there will be some distortion for transmitting a signal over a distance shorter than the wavelength)

Citation or clarification needed.

This is only true if the receiving antenna is basically wrapped around the transmitting antenna. From a practical perspective it doesn't happen, you'd just connect the wires directly and avoid the time domain issues you are referring to.

Re:Is this statement misleading? (1)

spottedkangaroo (451692) | about 5 years ago | (#29837329)

A HAM radio signal is really large. I was working with 80m radios, so the wavelength is literally 80m long.

I noticed huge deadspots in the room where there was almost no radio signal and other spots where it was distorted evilly.

This is called "nearfield" distortion. Generally speaking, receivers need to be at least one wavelength away to work reliably. Also, Tx antennae need to be at least one wavelength off the ground, or it changes the impedance of the whole array.

You can read about this on the wiki. I'd cite properly, but I'm sorry, I'm just not an engineer. I'm in CS.

http://en.wikipedia.org/wiki/Near_and_far_field [wikipedia.org]

Re:Is this statement misleading? (4, Informative)

slifox (605302) | about 5 years ago | (#29830641)

I think the OP was referring to data transfer bandwidth (the throughput, or data rate), rather than the traditional electronics use of "bandwidth" (referring to the width of the transmitted signal in the frequency spectrum; though "channel width" is a more exact term).

Of course higher carrier frequencies don't have a higher bandwidth, because bandwidth is a property of the whole system, including the data signal and modulation method. You can make the bandwidth as big or small as your system's constraints allow (e.g. one constraint might be to keep most of your transmitted power inside the allocated bandwidth).

If your data signal is modulated in the exact same manner regardless of the carrier, varying the frequency of the carrier will not affect the transmitted signal's bandwidth. The carrier frequency imposes the upper limit on the data signal's frequency, and thus a higher carrier frequency will theoretically allow for a high data rate.

Practically, however, the data signal is almost always much smaller than the carrier signal, and the transmitted frequency is subject to many other important factors such as noise, signal propagation through the environment, etc... In the case of 2.4GHz vs. 800MHz carrier frequencies, there is no practical gain in potential data rate.

This is all based on my limited understanding of communication theory. Please correct me and/or provide further details if possible!

Re:Is this statement misleading? (1)

kaiser423 (828989) | about 5 years ago | (#29831961)

You are correct.

But here's why most people associate higher frequencies with higher bandwidths: typically RF devices scale as percentages.

You're dipole that covers 10% bandwidth at 2.4Ghz is going to cover up to 200MHz of spectrum. You're dipole at 300MHz is only going to cover 30MHz. You can shove more data through 200MHz than you can 30MHz. Now, of course, you have to get that amount allocated, but the lower frequencies are packed, so the FCC typically gives out bigger chunks as you go higher in frequency.

Of course, you can use other antenna types, design you're traces and splitters, etc to cover more bandwidth, etc but it takes more money to build, making all the devices more expensive, and thus you're less likely to take off in the market because all of your equipment is so expensive.

So, yea, as a general public rule, higher frequencies = higher bandwidth, because that's typically how the dice roll for various cost and political reasons, but for us RF guys we want to know the allocated bandwidth, and what type of modulation they're using to cram that data in there!

Re:Is this statement misleading? (1)

commodore64_love (1445365) | about 5 years ago | (#29836409)

Rather than guessing you could just google "width of TV channel".

The answer is 6 megahertz. That's how much room these TV Band Devices (TVBD) will have for communicating over the internet. That's approximately 40 Mbit/s using 16VSB with a theoretical max of 96 Mbit/s if you strip all error correction.

Re:Is this statement misleading? (1)

Methlin (604355) | more than 4 years ago | (#29842045)

Rather than guessing you could just google "width of TV channel".

The answer is 6 megahertz. That's how much room these TV Band Devices (TVBD) will have for communicating over the internet. That's approximately 40 Mbit/s using 16VSB with a theoretical max of 96 Mbit/s if you strip all error correction.

16VSB would be 4 bits/symbol @ 6Msymbols/sec = 24Mbit without error correction (25.85 if you stay with ATSC's symbol rate of 6.46Msymbols/s). The wikipedia article on 16VSB is correct about bits/symbol then fails to get the math right about being "twice the data capacity of 8VSB" which is 3 bits/symbol.

Re:Is this statement misleading? (0)

Anonymous Coward | about 5 years ago | (#29830733)

It really doesn't matter what frequency when you're talking bandwidth. When you're talking size of the antenna or signal loss the wavelength might matter, but not for bandwidth. The reason you get more bandwidth here is because the spectrum is wider. The ISM spectrum is very very narrow and low power channels all bunched up around 2.4Ghz. With the new white spaces, they can use tons more and much louder. But, yes, they need longer antennas.

As far as the range? You can make a microwave signal go light years and a HAM signal go a few feet (although, there will be some distortion for transmitting a signal over a distance shorter than the wavelength). The range is more of a function of signal power.

No. The bandwidth of a signal is directly related to spectrum available for traditionally modulated carriers. Digital signals utilizing time division multiplexing can minimize this problem, however, QAM signals still need significant guard bands to prevent bleed over of signals. Less spectrum means fewer discrete channels which means TDM/QAM signals, which can only be pushed so fast. http://en.wikipedia.org/wiki/Bandwidth_%28signal_processing%29 (wikipedia)

Re:Is this statement misleading? (3, Insightful)

evilviper (135110) | about 5 years ago | (#29831247)

As far as the range? You can make a microwave signal go light years and a HAM signal go a few feet (although, there will be some distortion for transmitting a signal over a distance shorter than the wavelength). The range is more of a function of signal power.

You're horribly wrong.

Distance has everything to do with frequency. You aren't going to have shortwave/ham radio skipping around the world with a 2.4GHz transmitter no matter how much power you put into it. Similarly, there's a reason WiFi is popular at 2.4Ghz but the higher 5Ghz band used with the now-forgotten 802.11a standard has been vastly less utilized.

Frequency determines how well a signal will disperse around obstacles, and therefore, whether it will work AT ALL if you don't have 100% line-of-sight between transmitter and receiver.

Re:Is this statement misleading? (1)

MacAnkka (1172589) | about 5 years ago | (#29833247)

question: In eath atmospehere, different wavelengths travel different distances because some wavelengths get absorbedby oxygen in the air or water vapor, some travel over the horizon because they use reflect of the ionospehere, etc... But what about in a total vaccuum? Do different radio waves travel the same distance in a vaccuum?

Re:Is this statement misleading? (1)

evilviper (135110) | more than 4 years ago | (#29842601)

Do different radio waves travel the same distance in a vaccuum?

Not entirely... Higher frequencies will disperse less, so they can be broadcast in a much more narrow cone (see: high-gain antenna), so that a much stronger signal will arrive at the (much smaller) destination. Compare flashlight versus, eg., a laser, to see the difference.

OTOH, like on earth, lower frequencies will disperse around an obstacle, rather than being stopped entirely, so if there's any solid objects in the vacuum, the same principles apply as on earth.

Re:Is this statement misleading? (1)

drinkypoo (153816) | about 5 years ago | (#29833307)

OT, you just made me snicker at Microsoft. On the Xbox 360 they backed HD-DVD and 802.11a. Fail, fail.

Re:Is this statement misleading? (0)

Anonymous Coward | more than 4 years ago | (#29841205)

5 Ghz is alive and well in 802.11N equipment...

Re:Is this statement misleading? (1)

spottedkangaroo (451692) | more than 4 years ago | (#29844103)

I'm horribly wrong out of context, but perfectly correct if you think about it.

"They perform EME (earth-moon-earth) using microwave radios with regularity." (see below)

Frequencies have a lot to do with obstacles and path-loss, line of site, moving through water (or other mediums), but not distance.

Re:Is this statement misleading? (1)

evilviper (135110) | more than 4 years ago | (#29853795)

Frequencies have a lot to do with obstacles and path-loss, line of site, moving through water (or other mediums), but not distance.

Sure they do. Note that NASA, as you said, uses the highest frequencies they practically can. Distance has a lot to do with it.

Re:Is this statement misleading? (2, Informative)

mwilliamson (672411) | about 5 years ago | (#29831259)

Uh, no. Range is not a function of signal power. It more is a function of the overall signal/noise ratio and the sensitivity of the receiver. This includes noise introduced in the transmitter, natural/other noise, and noise introduced in the receiver. An antenna system with gain can both concentrate and attenuate signals, depending on the directivity and where its pointed.

BTW, I got over 1400 miles out of a little 0.3 watt ham signal, but thats no where near as impressive as Earth still being able to receive signals from Voyager 1 and 2 nearly 10 billion miles away. That's impressive.

-Michael

Re:Is this statement misleading? (1)

petermgreen (876956) | about 5 years ago | (#29833631)

Uh, no. Range is not a function of signal power.
Range is a measurement of how far you can go before path loss (note: many people think path loss is inverse square, this is only true in free space, there are a few situations where it is better and a load where it is much worse) reduces the signal to a level where the SNR is too bad to receive it. Crank up the transmit power and you increase the recieved signal power and hence improve the SNR at any given distance.

An antenna system with gain can both concentrate and attenuate signals, depending on the directivity and where its pointed.
Indeed it can, what this means is that antenna gain only helps you if you know something about the relative location of transmitter and reciever and can reasonablly arrange for them to be oriented correctly.

Re:Is this statement misleading? (0)

Anonymous Coward | about 5 years ago | (#29835247)

...except for that pesky horizon. ;-)

Re:Is this statement misleading? (1)

Grieviant (1598761) | more than 4 years ago | (#29843345)

Uh, no. Range is not a function of signal power. It more is a function of the overall signal/noise ratio and the sensitivity of the receiver. This includes noise introduced in the transmitter, natural/other noise, and noise introduced in the receiver. An antenna system with gain can both concentrate and attenuate signals, depending on the directivity and where its pointed.

BTW, I got over 1400 miles out of a little 0.3 watt ham signal, but thats no where near as impressive as Earth still being able to receive signals from Voyager 1 and 2 nearly 10 billion miles away. That's impressive.

-Michael

This post is horribly misleading. If range wasn't a function of signal power, why on earth don't we have handsets which operate with microwatt transmit power instead of (typically) something on the order of a tenth of a watt?

Range is certainly a function of transmit power. If you have line of sight between the transmitter and receiver, every factor of 4 increase in transmit power (6 dB) doubles your range. It should be pointed out that often times we don't have line of sight for cellular, even when the base station is sitting on a high rooftop, so the range vs power gains will be less than ideal.

Any increases in range achieved by raising transmit power are above and beyond (independent of) those you get from using directional antennas. I'll spare you the insult of linking a free space path loss article. Obviously, not every wireless communications system is a fixed installation which can take advantage of directional antennas - cell phones need the capability of receiving from any direction, for example - so, in many cases of practical interest, there isn't an option to increase range via antenna directionality.

Lastly, noise introduced at the transmitter is meaningless because it is of much smaller power than the signal and suffers the same channel attenuation before reaching the receiver. Actually, it wouldn't even be properly considered noise in that case - it would an undesired emission, possibly violating whatever EMI / RFI spectral mask regulations govern communication in the band of interest. There's a reason why link budget calculations are always based on noise / inteference at the receiver.

Re:Is this statement misleading? (3, Informative)

niko9 (315647) | about 5 years ago | (#29831707)

You can make a microwave signal go light years and a HAM signal go a few feet

Just for clarification, ham radio operators operate in the microwave region as well. They perform EME (earth-moon-earth) using microwave radios with regularity.

Some info here: http://www.dxzone.com/catalog/Operating_Modes/EME/ [dxzone.com]

Re:Is this statement misleading? (1)

spottedkangaroo (451692) | about 5 years ago | (#29837379)

The more HAMs I meet, the more I think they do everything. :p

Re:Is this statement misleading? (1)

stonefoz (901011) | about 5 years ago | (#29833295)

When TV started it grabbed a large chunk of the sweat spot between realistic antenna size and signal that'll pass through trees, walls, over small hills. Two low of a freq and the antenna has to match, low freq big antenna, high freq and doesn't pass through anything. So for a realistic link across either rural nothing and trees, or urban towers and noise, tv hold's about half of all desirable frequencies. While I wait to see how this range will be managed, anything is better than handing over half the realistically usable space to TV stations than only utilize a small percent of the spectrum in what was one of the most wasteful methods possible. Analog TV did nothing to try and reduce space occupied. Signal was only modulated in means that would allow transmission, no filtering, sync required spikes in size, nothing but waste. This is a huge amount of bandwidth that can be used. Each TV channel occupies 10mHz and with the simplest of digital encodings, bpsk, enables 10mBPS. BPSK routinely is used withing a few percent of theoretical minimal power to achieve reception. By transiting more than merely two types of signals, with slight power requirement increase, typical equipment transmits 16, 32, or 64 signal variations. Within just on TV channels space 640mBPS. It's a joke that this hadn't been done sooner.

Re:Is this statement misleading? (1)

commodore64_love (1445365) | about 5 years ago | (#29836863)

>>>Analog TV did nothing to try and reduce space occupied...nothing but waste.

This statement couldn't be more wrong. Why do you think analog television is interlaced rather than progressive scan? Answer: The engineers made that decision to save space and reduce the channel size from 12 to 6 megahertz. Why do you think they overlaid the color image with a nominal resolution of only 160x486? Again, to save space. Analog did "nothing" to reduce space is not an accurate representation of the work done by the 1930s' engineers.
.

>>>anything is better than handing over half the realistically usable space to TV stations

Hold on. My only television reception is by antenna - as is true of many Americans living in rural areas. We've already given-up 40% of our channels (1, 15-19, 34, and 51 to 83). How much more will wireless/cellphone users demand? Maybe you don't watch much TV, but *I* do and I was here first. Don't take away our free television.

Re:Is this statement misleading? (1)

stonefoz (901011) | about 5 years ago | (#29839525)

Color was added after the signal spacing was established, nothing was changed but color. Interlacing makes the receiver requirements cheaper. Vertical scan was already driven at over 1MHz. High power is required to move the vertical scan, high power + fast = expensive. . How many other 1930 technologies are still one the air? AM radio occupies a spectrum that's inhibitory difficult for any other use, and TV is left as the only other wagon wheel left running. There was great work done, but conservation was not one of them. As for the argument of scarcity of alternatives, I also live in rural, podunk, Kentucky. Rural programing sucks. It's prohibitively expensive to transmit with enough power to spread TV across the country. I get three channels, all big media, and one that even with the help of ### large broadcaster, can not find means to stay on the air. There is currently two satellite tv providers with some scarce FTA working outside the bounds of general broadcast. If you wish to lobby for channels, please, consider lobbying for FTA. Radio is public property, allocated for what would hopefully be the better good for all. TV is helping a minority while claiming a majority of resources. Wagon wheels where here before cars, but I don't dare impose 15mph to oncoming traffic, racing down the interstate. If technology give means to better utilize resources, you're an asshole for slowing down the rest of us. Anything would be better.

Re:Is this statement misleading? (1)

commodore64_love (1445365) | about 5 years ago | (#29837039)

>>>Each TV channel occupies 10mHz...space 640mBPS

Also your numbers are wrong. 10 millihertz? 640 millibits/s? I'm going to assume you mean 10 Megahertz which is still not correct. Each channel spacing is 6 or 8 MHz, and the maximum theoretical bandwidth on these channels is 96 and 128 Megabits/s respectively, although a more realistic speed with 16VSB or COFDM plus error correction is only 40-60 Mbps - nowhere near 640.

Re:Is this statement misleading? (0)

Anonymous Coward | about 5 years ago | (#29834559)

But it is not only the size of the antenna that matters - antennas have a bandwidth as well. It is much easier to get an antenna to have a 20 MHz bandwidth at 2 GHz carrier (1%) than 20 MHz BW at @ 200 MHz (10%). So yes, carrier frequency does matter when talking bandwidth.

As a broadcast engineer... (5, Interesting)

jjoelc (1589361) | about 5 years ago | (#29829707)

while I am personally glad this finally went through... I can vouch for the potential issues this can cause with existing broadcasts. ATSC is so sensitive to multi-path as it is... (and other forms of interference to boot, but I digress) Throwing out a bunch of unlicensed transmitters, borrowing the space between TV stations is a very scary proposition.

Re:As a broadcast engineer... (1)

drinkypoo (153816) | about 5 years ago | (#29831499)

What's scary to me is how important broadcast TV is to so many. Internet access is far more useful than TV, not to mention, you can watch TV on it. As far as I'm concerned it makes more sense to use every bit of spectrum currently allocated for television to provide ubiquitous wireless internet access.

Re:As a broadcast engineer... (1)

jjoelc (1589361) | about 5 years ago | (#29836029)

If they can figure out a way to implement something like the Emergency Alert System [Wikipedia] on the internet, you might be able to convince me (And a lot of other people) {they are currently working on updating the EAS system, including an IP protocol... the trouble is that IP is by design a fault tolerant protocol, and Emergency alerts are by nature NOT [they HAVE to get through, is what I mean]) There are some very specific requirements for EAS and they are having a lot of fun talking about the future possibilities on the web... Then reality gets in the way and we are back to square 1.

Re:As a broadcast engineer... (1)

drinkypoo (153816) | more than 4 years ago | (#29841633)

If they can figure out a way to implement something like the Emergency Alert System [Wikipedia] on the internet, you might be able to convince me

I would suspect that it should be possible to railroad connections using packet inspection and mangling and railroad people off to a page, video stream, audio stream, Autocad document, or whatever. It would be a fairly brutal thing to do, but it would be functionally equivalent to BEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEP and a blue screen on your TV. Of course, the repercussions are significantly more severe. On the other hand, the EAS already doesn't help me if I am one of the many who have given up on broadcast television and radio entirely. And, uh, I am. It's not like I "don't watch TV" but I don't watch broadcast TV. I rent TV shows via Netflix.

Re:As a broadcast engineer... (1)

commodore64_love (1445365) | about 5 years ago | (#29837099)

I'm not buying it. Wireless internet is already using ten times as much bandwidth as broadcast television, and it still can't provide the same level of service.

Also, speaking frankly, my local television sucks which is why I watch distant signals from Baltimore and Richmond (about 60 miles in opposite directions). If the TV Band/whitespace Devices block my access to these cities due to transmitting directly over the stations, then I'm going to track down the gadgets and politely ask the owner to turn them off. And if they refuse, per Class B regulations, I will terminate the broadcasts. If that means using a hammer so be it.

I've been watching television for over 50 years - you do not have a right to start using your iPods or whatever to transmit over-top the TV signals.

Re:As a broadcast engineer... (1)

sosume (680416) | about 5 years ago | (#29833651)

It seems to work well .. but wait I suddenly have a splitting headache, be right back ...

It's Obvious Where This is Heading (5, Interesting)

segedunum (883035) | about 5 years ago | (#29829789)

Interested parties (whose businesses rely and will expand with cheap or free bandwidth) are angling to use it as a means to get around current mobile operators, and it can't come a moment too soon in many ways as far as I'm concerned. However, I can only see this being a recipe for disaster given the state of many wireless devices and all their broken firmware updates today if it's accurate:

Devices must both consult an FCC-mandated database to determine which channels are available for use at a given location, and must also monitor the spectrum locally once every minute to confirm that no legacy wireless microphones, video assist devices or other emitters are present.

Webcams? (2, Interesting)

d0rp (888607) | about 5 years ago | (#29829795)

I'm confused... what do they need webcams for in this project? I actually read the article and it didn't mention what they were for either.

Re:Webcams? (3, Informative)

John Hasler (414242) | about 5 years ago | (#29829875)

The school system is using them for "distance learning". They aren't really relevant to the story.

Re:Webcams? (3, Funny)

HangingChad (677530) | about 5 years ago | (#29831293)

I'm confused... what do they need webcams for in this project?

Live porn. Hey, you have to fill that broadcast schedule with something.

mod dDoWn (-1, Offtopic)

Anonymous Coward | about 5 years ago | (#29829823)

live and a job to log on Txhen the

Re:mod dDoWn (-1, Offtopic)

LordKaT (619540) | about 5 years ago | (#29829883)

What the fuck happened to this post?

Oh (-1, Flamebait)

Anonymous Coward | about 5 years ago | (#29829871)

I thought it was some kind of KKK internet...

Let me guess... (1)

BigWhiteGuy_27 (804307) | about 5 years ago | (#29829895)

...its powered by a bunch of Python scripts?

100mW!? (1)

mirix (1649853) | about 5 years ago | (#29829919)

Seems rather pathetically low power to me.

I can't see them getting too much range out of that, not to mention that lower freqs = bigger antennas.

But more BW is always nice.

Re:100mW!? (1)

John Hasler (414242) | about 5 years ago | (#29829969)

Those frequencies are largely unaffected by foliage and the walls of buildings, unlike the microwave frequencies used by WiFi. They also propagate over the horizon somewhat.

Re:100mW!? (1)

Tiger4 (840741) | about 5 years ago | (#29830081)

Low power, and small antennas is probably a good thing here. Small antennas will have poor efficiency, low power will mean short range. Combined it means the footprint for a given transmitter will be small. More can be put into a given community without undue interference. If anyone wants to put a 5 foot TV aerial on their laptop or Blackberry, they have way more need for this spectrum than the average Joe or Jane.

Re:100mW!? (1)

mirix (1649853) | about 5 years ago | (#29830707)

Right, I agree.
The part I don't understand is, why are they spinning it as "long range" & "a wifi killer" then?

Re:100mW!? (1)

CompMD (522020) | about 5 years ago | (#29835791)

The average wifi card in your laptop has a 30mW transmitter, seems rather pathetically low power to me.

100mW in VHF with the proper antenna has much better range than a wifi card at the same power with a proper antenna. For comparison, police walkie-talkies have transmit powers between 1W and 5W usually, and they can cover huge areas.

wif fi, that was invented by... (2)

MrKaos (858439) | about 5 years ago | (#29829957)

The people at the CSIRO [youtube.com] wasn't it?

enjoy :-)

Why Claudville? (3, Interesting)

molo (94384) | about 5 years ago | (#29830001)

Why Claudville? According to the Wikipedia page, there are around 20,000 people in the entire county. And according to the FCC DTV maps, they can only expect to receive two (!) TV stations, both from the Winston-Salem, North Carolina area. See here: (enter Claudville, VA) http://www.fcc.gov/mb/engineering/maps/ [fcc.gov]

That is perhaps why they are testing it there. Its not hard to avoid active TV channels if there are only two.. and they are on adjacent RF channels (31 and 32).

-molo

Re:Why Claudville? (2, Insightful)

Obfuscant (592200) | about 5 years ago | (#29830399)

And according to the FCC DTV maps, they can only expect to receive two (!) TV stations,

You didn't read the "maps" correctly. They are expected to get two STRONG signals, and 6 weak ones. The weak ones are on UHF 19, 29, 51, 33 and 14.

If the "white space" devices in that area are as capable of reading the maps as you are, those people WILL only get two stations instead of the 8 they might, especially those people who have invested money in good outside antennas so they CAN get the other weak signals.

But they're hicks who don't deserve TV anyway, right?

Re:Why Claudville? (0)

Anonymous Coward | about 5 years ago | (#29830547)

The internet is going to eat TV alive anyway. The faster this happens the better it is for everyone including people who live in rural areas. Taking away a few TV stations and giving people free broadband is like taking away their horses and giving them free cars. Stop clinging to ancient technology,

Re:Why Claudville? (1, Insightful)

Anonymous Coward | about 5 years ago | (#29830719)

If they have an outside antenna, it's going to be highly directional.

Re:Why Claudville? (1)

profplump (309017) | about 5 years ago | (#29831263)

Because outdoor antennas are necessarily high gain?

Re:Why Claudville? (1)

petermgreen (876956) | about 5 years ago | (#29833689)

In my experiance outdoor antennas are usually a lot larger with a lot more elements than set top ones and presumablly this means they are higher gain.

Re:Why Claudville? (1)

commodore64_love (1445365) | about 5 years ago | (#29837213)

>>>If they have an outside antenna, it's going to be highly directional.

(1) No. My CM 4228 is directional but not "highly" directional, since it still gets signals from the rear and side. (2) Directionality doesn't matter if the TV Band/whitespace Device User is standing between me and whatever station I'm trying to watch.

"Well honey I wanted to watch the Yankees game on channel 19, but unfortunately our neighbor is using his iPod on the same channel."

Re:Why Claudville? (2, Funny)

plover (150551) | about 5 years ago | (#29831011)

Why Claudville?

I'm not from Virginia, you insensitive Claud!

Re:Why Claudville? (1)

suso (153703) | about 5 years ago | (#29833533)

Because Claudville sounds like Baudville. *shrugs*

Wifi on STEROIDS!?!! (2, Funny)

Cajun Hell (725246) | about 5 years ago | (#29830109)

Please, think of the example this is setting for the children. Congress should immediately hold hearings about Wifi cheaters.

I don't think that word means what you think it... (5, Funny)

owlnation (858981) | about 5 years ago | (#29830735)

"First Public White-Space Network Is Alive"

I think you mean "live". If it's "alive" we have some real problems ahead of us.

It's so esoteric (0)

Anonymous Coward | about 5 years ago | (#29831037)

What next, a Brainfuck [wikipedia.org] network?

There? (1)

redneckblues (1045788) | about 5 years ago | (#29831141)

My Grandma and other realtives live out there and I just did a double take. Would not expect that place to have gotten it first.

Security? (1)

Necrotica (241109) | about 5 years ago | (#29831151)

White space network, eh? I wonder if the security architect implemented true network segregation?

Re:Security? (1)

trouser (149900) | about 5 years ago | (#29831695)

No blacks, no Irish, no dogs.

Possibly stupid questions (2, Interesting)

Aokisensei (1605857) | about 5 years ago | (#29831573)

So this white space is "unlicensed"? Completely? What, if any restrictions are there on usage of it? Is it at all possible in the foreseeable future that there will be consumer-level devices for this type of frequency? Like routers and other networking equipment, or is this really more for just companies to provide service? Also, what kind of range can you expect on this band at 'normal' power levels?

Re:Possibly stupid questions (1)

commodore64_love (1445365) | about 5 years ago | (#29837313)

(1) No it's licensed to TV broadcast.

(2) TV Band/whitespace Device users are expected to turn-off their gadgets if they interfere with licensed stations (WABC, WCBS, WFOX, et cetera). However if they refuse there's no real punishment.

(3) Yes TV Band Devices are expected to be used by average people, so expect iPods and other gadgets to soon be transmitting over channels 2 through 51.

(4) Range is probably 1-2 miles same as today's cellphones but with enough power to drown-out television reception of stations greater than 30 miles distance. Interference with cable channels is also possible if the TVBD is near an unterminated wall inlet.

Whitespace (1)

Hazelfield (1557317) | about 5 years ago | (#29836319)

What? An entire network protocol written in Whitespace? That must have been hard as hell!

Test (0)

Anonymous Coward | about 5 years ago | (#29836497)

Test virginia

Check for New Comments
Slashdot Login

Need an Account?

Forgot your password?