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Pushing Wi-Fi's Limits: Problems and Solutions

Posted by CmdrTaco on from the bits-and-bytes-wizzing-around-your-noggin dept.

securitas writes "Forbes technology columnist Arik Hesseldahl discusses the problems with 802.11x Wi-Fi - speed and range - and how to push its limits in a pair of his Ten O'Clock Tech columns. He discusses the alphabet soup of Wi-Fi standards, so-called 'Super G' dual channel bonding that allows two of 11 channels to act as one (and the interference problems that ensue), and the multiple input/multiple output (MIMO) method 'using multiple antennas to break a single, high-rate signal into several lower-rate signals' that could be a solution. Pushing Wi-Fi's Limits, Part Two focuses on repeaters, Wi-Fi mesh networks, WiMax and a company called BelAir Networks that has deployed several Wi-Fi mesh networks."

80 comments

  1. fp by Anonymous Coward · · Score: -1, Offtopic

    fp

    1. Re:fp by Anonymous Coward · · Score: -1, Offtopic

      gj

  2. A netgear by Zorilla · · Score: 1, Funny

    Hey look! A netgear Wireless router sitting right there. I can make a first post without getting my IP ba...[Wireless Signal: Weak]..........[Wireless Signal: Good].......

    crap! Failed it!

    --

    It would be cool if it didn't suck.
    1. Re:A netgear by Anonymous Coward · · Score: 1, Funny

      Obviously this individual is paid by Linksys to bash Netgear wireless routers. Don't fall for the propaganda! You know, the "[Wireless Signal: Weak]" stuff is faked--he just typed it in!

      This is the last time I buy a Linksys router or any other Cisco product, for that ma

    2. Re:A netgear by periol · · Score: 1

      i've had to test a few wifi routers, and the buffalo routers [buffalotech.com] have significantly outperformed anything from linksys, netgear, or d-link. i recommend them to everyone i work with.

    3. Re:A netgear by Etobian · · Score: 1

      I'll bash BOTH Netgear AND Linksys: BOTH are too chickenshit to issue Linux drivers for their 802.11g cards, or even ALLOW anyone to create those drivers.

    4. Re:A netgear by pyrrhonist · · Score: 1
      or even ALLOW anyone to create those drivers.

      Bullshit!

      There are Linux drivers for both Prism and Atheros chipsets, which are used in Linksys and Netgear cards.

      --
      Show me on the doll where his noodly appendage touched you.
    5. Re:A netgear by Etobian · · Score: 1

      I have a Linksys WMP54G. It has a Broadcom chip. Which Linksys 802.11g card has either a Prism or Atheros chip?

    6. Re:A netgear by Wicksta · · Score: 1

      Are you going to apologise to Netgear or just pretend you didn't mention them in your previous post?

    7. Re:A netgear by pyrrhonist · · Score: 1
      I have a Linksys WMP54G. It has a Broadcom chip.

      Ahhhh, yes. Broadcom has never been very friendly towards driver developers.

      The good news is, your card works under Linux with NdisWrapper.

      Which Linksys 802.11g card has either a Prism or Atheros chip?

      The WUSB54G has a Prism Chipset.
      The WPC55AG and WMP55AG have Atheros chipsets.

      --
      Show me on the doll where his noodly appendage touched you.
  3. You know why they want to do this... by Anonymous Coward · · Score: -1, Troll

    Microsoft alongside the CIA wants to be able to watch everything you do and where you are from anywhere

  4. Commandant Taco: Nazi Chef by Anonymous Coward · · Score: -1, Offtopic

    You're doomed to a life of loneliness you will never find anyone who truly loves you even your parents regret your birth you spend all your time chatting with fake friends on the modem and you spend the rest of your time playing with operating systems and other boring shit go back to watching tv because that escapist shit is the best you will ever get faggot die die die die die die die tit ass nig ger

  5. Cool by IWantMyNickBack · · Score: 1

    I want a mesh net!

  6. Real issue by kneecarrot · · Score: 5, Informative

    While standards and spectrum sharing are definitely factors, hardware must move quite a bit forward if it is going to become more useful than small home networks and looking cool at a Starbucks. The real problem right now is the quality of the radio chips coming out of Taiwan. They are typically way under specified range and allow for alot of bleeding between channels. The average home user won't notice it, but when you are rigging up multi-antenna setups or relying on precise timing for a repeater, it matters to a HUGE extent.

    --

    I always save my last mod point to mod up a good troll. You people are too serious.

    1. Re:Real issue by Anonymous Coward · · Score: -1, Offtopic

      How many home users rig up multi-antenna setups?

      It's all about the economics of democracy.

    2. Re:Real issue by Anonymous Coward · · Score: -1, Offtopic

      Why is it so hard to at least read what you are replying to? Idiot.

    3. Re:Real issue by Jeff+DeMaagd · · Score: 4, Insightful

      One thing that scares me is the multi-channel radios. There are effectively only three non-overlapping channels, and some APs are starting to take up two of them? I know the spectrum is unlicenced for low power, but I think that's usually just rude and mean for one person to just take two channels. Right now, I experiment with three APs being on, all three channels, but being in a rural area and having checked with all the neighbors, no one else is using the spectrum near me.

  7. I wonder how healthy it is by 2057 · · Score: 3, Interesting

    I wonder how healthy it is to be surrounded day in and day out by all these microwaves and such....

    --
    For The Best Jazz/Hip-hop fusion > COlD DUCK
    1. Re:I wonder how healthy it is by IWantMyNickBack · · Score: 2, Insightful

      Bah... We already have AM, FM, TV, and all other sorts of signals going through us... we arent seeing any adverse side-effects, are we?

    2. Re:I wonder how healthy it is by MikeXpop · · Score: 3, Insightful

      How would we know?

      --
      Etiquette is etiquette. He kills his mother but he can't wear grey trousers.
    3. Re:I wonder how healthy it is by Jason1729 · · Score: -1, Offtopic

      Put a piece of raw meat in your microwave. Set it for 15 minutes. Look at it when the 15 minutes are up and you can answer your own question.

      Jason
      ProfQuotes

    4. Re:I wonder how healthy it is by mOoZik · · Score: 5, Interesting

      All the popular notions of microwaves being harmful are pretty unfounded. You must remember, they're like other waves, like radio, UV, IR, radar, and so forth. It seems to me most misconception arises from the fact that we use microwaves to cook food and that stray waves from cell phones and other such things could be harmful to us, but again, this is untrue for most purposes.

      You see, microwaves excite water molecules - they make them move back and forth really fast - thus heating them and increasing their temperature; this is how a microwave oven works. The fear with cell phones (which have a very weak transmitter) is that they may increase the temperature of brain cells or other, critical cells above a normal temperature, thus cause an unfavorable outcome. However, studies have shown that the increase of temperature from a cell phone antenna - when put against one's ear - is less than 1/10th of a degree Centigrade. As you can imagine, this is insignificant; our bodies are able to remain undamaged at temperatures MUCH higher than this.

      The point is that cellphones, while not the topic of this article, transmit much more powerful microwaves, much closer to the head. This means most WiFi waves are not at all powerful enough to have an impact.

      Of course, I do not suggest you stick your head near a multi-megawatt microwave transmitter.

      --
      A blog like any other.
    5. Re:I wonder how healthy it is by kid+zeus · · Score: 1
      Bah... We already have AM, FM, TV, and all other sorts of signals going through us... we arent seeing any adverse side-effects, are we?

      Not unless you count the positively MASSIVE increase in cancer in the 20th Century. According to NIH, the rate of cancer increased 64% just between 1970 and 1997.

      Granted, it's pretty hard to tell whether that's from all the e-m waves flying through the air (or through our walls and under the ground we walk and live on) or from the pesticides and chemical additives (e.g., sacharine, aspartame, etc.) in our food, a change to an unhealthy meat/fat-laden diet, a rise in tobacco use or industrial poisons spewed into the air. But if you think the rise in incedence of such diseases and the increase in pollution (including e-m pollution) across the spectrum is purely coincidental, I have a bridge to sell you.

    6. Re:I wonder how healthy it is by tonyr60 · · Score: 1

      Well you could try counting sperm... http://www.theregister.co.uk/2004/06/28/mobile_bal l_rot/

      "Carrying a mobile phone can reduce a man's sperm count by as much as 30 per cent, according to Hungarian scientists."

      Fortunately us geeks have WiFi access to lots of porn so it should not be too difficult....

    7. Re:I wonder how healthy it is by jdhutchins · · Score: 3, Insightful

      The rate of cancer that we found went up 64% between 1970 and 1997. That doens't necessarily mean there was 64% more cancer, it just means we know how to find cancer better. I'm not saying that cancer hasn't gone up any, but it's probably not that dramatic.

    8. Re:I wonder how healthy it is by PurpleFloyd · · Score: 2, Informative
      If you think that correlation implies causation, then I have an Eternal Life Braclet to sell to you.

      The only way to determine the cause of an effect is via scientific experimentation - a double-blind study with experimental and control groups. We could, for example, take 100 mice, leave 50 in "normal" cages, and put the other 50 in cages near to a broadband EM source. Then, we examine the rate of cancer in each group - if it goes up, then and only then can we say that "electromagnetic radiation (at a certain level) causes cancer in mice, which are similar enough to humans that we can safely say to stay away from EM sources."

      There could well be many other reasons for the higher cancer rates reported in the 20th century - in addition to all the reasons you have mentioned, people have started to live much longer; if you die from cholera or typhoid fever at 25, you won't live long enough to die from cancer at 65. Also, the broad penetration of medical care into the working class, as compared to the 19th century, means that deaths which previously had no known cause might now be easily diagnosed as cancer. There are many reasons why reported cancer rates might go up - an actual rise in the cancer rate is only one of them.

      --

      That's it. I'm no longer part of Team Sanity.
    9. Re:I wonder how healthy it is by Anonymous Coward · · Score: 0

      This "research" did not, according to Times, check anything besides mobil phone use and sperm count. Factors like that the heavy mobile phone users were more stressed (known factor of reduced sperm count) or lived in polluted cities (another known factor).

      Comparable "research" is the observation that you should never take an ambulance, as the people taking ambulances dies more often than the people taking cabs.

    10. Re:I wonder how healthy it is by uncommonlygood · · Score: 2, Interesting

      Put a piece of raw meat in your microwave. Set it for 15 minutes. Look at it when the 15 minutes are up and you can answer your own question.

      Yeah, do it on "defrost" and it you won't be so scared, and the oven would still be pumping out about 1000 times more power than a wi-fi card.

      Someone once told me (with a completely straight face) that a mobile phone generates enough microwaves in an hour to boil an egg. Well, I get a lot of free minutes per month with my phone that I don't normally use, so we put the phone right next to an egg and rang my house for an hour. Guess what, it didn't boil.

    11. Re:I wonder how healthy it is by NanoGator · · Score: 1

      "I wonder how healthy it is to be surrounded day in and day out by all these microwaves and such...."

      What's it been, 3 generations so far?

      --
      "Derp de derp."
    12. Re:I wonder how healthy it is by Anonymous Coward · · Score: 0

      Yeah they thought about health effects when they named the standards:

      GSM = Gammarays Sacrificing Mind
      NMT = Neutrons Making Tumor

    13. Re:I wonder how healthy it is by Jason1729 · · Score: 0, Offtopic

      First, it was a joke with some basis in fact and your attempt to refute it included plenty of fact to base the joke on.

      Using your own number of 1000 times more powerful; so that 15 minutes experiment shows you what 15000 minutes of exposre does. 15000 minutes is less than 11 days; it's not that much.

    14. Re:I wonder how healthy it is by aXis100 · · Score: 2, Interesting

      The effect of microwaving a piece of meat is due to the power level, not the overall exposure.

      1000 Watts of a microwave heats the meat enough to cause cooking. The rate at which energy is added is higher than the rate it dissipates, so the equilibrium temperature goes up.

      30mW from a wifi device does not cause enough of a temperature increase to cause any harm.

    15. Re:I wonder how healthy it is by Anonymous Coward · · Score: 0

      Depends how you define harm; I consider Cancer pretty harmful, but if you don't then you're right. Exposure to radiation causes cancer and it's cumulative over a life time. If you get the same exposure in 5 seconds or 20 years, it's the same amount of damage.

  8. A clever concession to state of the market. by ofdm · · Score: 5, Interesting
    This solution seems to be quite a clever approach. A fundamental problem with 802.11b is the lack of spectrum. Although the channels are labelled 1 to 11 (in the USA), the numbers refer to a spacing of 5MHz chunks over 50MHz in the 2.4GHz ISM band. The problem is that the 802.11b signal uses almost 4 of those channels to actually transmit data. As a result, in order to have systems on different frequencies which are not interfering with each other, you end up with three effective channels - 1, 6, and 11. (If you have a WiFi AP accessible, check what channel it's on - most likely it will be one of those). Due to the low number of channels, it's impossible to do much in the way of channel planning. The result is that adjacent APs have to share the spectrum. The net outcome is that the data rate that users get between their client and the AP is reduced.

    802.11a at 5GHz was supposed to solve this. The 5GHz band is notable because of the extra spectrum it has. Compared to the 3 effective channels at 2.4GHz, the 5GHz UNII band has (again, it depends on your country) at least 8 usable channels of 20MHz. Additionally, the link rate is between 6 and 54 Mbps (as compared to 1 to 11Mbps for 11b, although this is somewhat moot given the growing preponderance of 11g solutions at 2.4Ghz). However, the 802.11a market never really took off and killed the 11b market the way we (engineers) expected it to. Mostly due to good (if slippery) marketing of 11g. As a result, there's a lot of unused 11a spectrum begging to be used. There are a lot of people with 2.4GHz equipment who want more range without losing data throughput. Using the 11a spectrum to extend the 11b/g range is what these guys have done. Neat - they get to use a superior technology with cheap chips available, to leverage a large market (albeit of dullards wed to an inferior solution).

    1. Re:A clever concession to state of the market. by nmos · · Score: 1

      The problem with 802.11a is that the range is typically even more limited than 802.11b/g. As for this mesh, it sounds like a pretty expensive proposition. They'll need two radios and two antennas per unit and units probably every few hundred yards/meters. Ask Ricochet/Metricom how much it costs to put that much equipment in place. Also you lose speed with each hop so there is goint to be a lot more than just one or two wired nodes in even a small city.

    2. Re:A clever concession to state of the market. by ofdm · · Score: 1
      802.11a ... range is typically even more limited than 802.11b/g
      In reality, 11a range, for the same transmit power, is not that bad compared to 11b. The limit to range is the sensitivity of the receiver - at what received signal strength does the packet error rate drop to an unacceptable level - usually taken as 10% but in reality somewhere between 1% and 10%.

      For a well designed 11b receiver, the receive sensitivity for 1Mbps data rate is around -94dBm (i.e, the signal is about as strong as the noise at the receiver, and here we mean the noise floor due to the sky itself plus the receive amplifiers etc).

      For an 11a receiver, the receive sensitivity for its lowest rate (6Mbps) is around -87dBm, which is to say the receiver needs 7dB or about 4 times as much power to receive 6Mbps as 1Mbps (not a bad tradeoff when you recall that you're receiving 6 times as much data).

      Solutions to this: up the transmit power, or use high gain antennas for the 11a. (This is limited to an extent by FCC transmit spectral mask rules). At the same time, drop the transmit power on the 11b. This means that

      1. The 11b range has been reduced - sharing the spectrum with fewer users, thus upping the throughput each user gets
      2. The 11a range has been increased so that it is larger than the inter-cell(11b) spacing, allowing the cell APs to be meshed.
      Beautiful.

      (FWIW, I don't have any relationship with these people)

    3. Re:A clever concession to state of the market. by ttsalo · · Score: 2, Interesting
      The result is that adjacent APs have to share the spectrum.

      I once thought up a solution for this. The APs could have active antennas with a grid of elements, much like modern military radars. This sort of antenna is directional and the beam is electronically steerable. As long as there was a different band for downstream and upstream, interference would be virtually eliminated. Finding the client's direction and the schedule for listening to the clients would have to be somehow solved.

      This sort of AP wouldn't be exactly cheap, though...

      --

      --
      If the road to hell is paved with good intentions, where does the road paved with evil intentions lead to?
    4. Re:A clever concession to state of the market. by HeghmoH · · Score: 1

      It exists, look at http://www.vivato.net/. It is a bit pricey, though; I'm too lazy to find it on their site right now, but I looked before, and it ran on the order of ten thousand dollars a copy.

      --
      Mod down posts with a "Free Mac Mini/iPod" sig, they're spam!
    5. Re:A clever concession to state of the market. by Jeff+DeMaagd · · Score: 1

      How much different is the propagation of 5 GHz RF vs. that of 2.5 GHz in air? I thought it gets blocked a lot more readily by trees and such too.

    6. Re:A clever concession to state of the market. by ofdm · · Score: 1
      It's a lame answer, but ... it depends. Going from 2 to 5 GHz does result in an increase in attenuation, particularly the exponent in the expression. Another obvious change is the multipath. At 5GHz it's somewhat narrower band than at 2.4GHz (simply due to the relationship between delay and carrier frequency), which has benefits in the OFDM rates because the FEC across subcarriers works better with narrow-band fading. At 5Ghz, the signal beam doesn't defract quite as much as 2GHz, so trees etc are slightly more opaque, but off the top of my head I can't say just how much.

      As a general comment, the frequency dependence of range exists, but isn't as significant as the extra signal needed by the OFDM rates.

  9. pushing the limits of the pateNTdead PostBlock by Anonymous Coward · · Score: -1, Offtopic

    censorship devise. it's just whoreabull.

    from yet another post titled:

    worst pc MiStake in the history of the unixverse?

    that would be trustworthycomputing.com, & it's not even an accideNT?

    another previously PostBlocked post? today's storIE?

    also right up there, along with gnu online dating, is robbIE's fauxking PostBlock censorship devise. again, no accideNT.

    endangered specIEs on the internet? (Score:mynuts won, not funnIE, again)
    by Anonymous Coward on Sunday July 04 (ind. est. 2004?), @08:55AM (#9605297)
    kind of rhymes with feekeys.

    the badtoll for yOUR 'independence' being extracted from you buy yOUR owned corepirate nazi felon glowbull warmongering execrable, is absolutely unpayable by any population. lookout bullow.

    all is not lost.

    consult with/trust in yOUR creators.... doggedly rebuilding civilizations since/until forever. see you there?

    "We have a train wreck that's definitely going to happen,'' Harris said. ``We have conflict of interest, we've taken the checks and balances away, and we know the votes are already being miscounted fairly frequently. This is going to be huge.''

    Harris, 52, didn't set out to become a muckraking voting technology expert.

    Accustomed to working with manuscripts and authors in suburban Seattle, she preferred doting on her new grandchild to debating politics. She still doesn't vote regularly.

    But when Harris was idly surfing the Web during a lunch break two years ago, she became obsessed with an issue essential to democracy, quickly becoming the unlikely center of a movement to ensure integrity in the nation's voting systems.

    Critics say Harris, author of ``Black Box Voting: Ballot Tampering in the 21st Century,'' is a fear-mongering grandstander and a presumptuous conspiracy theorist. The prime target of one investigation -- voting equipment maker Diebold Inc. -- says her antics undermine democracy.

    ``We must not frighten voters or inadvertently provide any type of disincentive to voting,'' Diebold spokesman David Bear wrote in an e-mail when asked to respond to Harris' claims that the company's software is riggable and insecure. ``While security is an important issue ... improvements can and will be made.''

    Others question the motives behind her obsessive investigations of politicians and executives at big voting equipment companies such as Diebold, Sequoia Voting Systems Inc. and Election Systems & Services Inc.

    ``She bases her whole theory on a continuous string of untruths,'' said Lou Ann Linehan, chief of staff for Nebraska Sen. Chuck Hagel. In the 1990s, Hagel headed voting equipment company American Information Systems Inc., which later became ES&S. Hagel maintains investments between $1 million and $6 million in McCarthy Group Inc., a private bank with a large stake in ES&S.

    Harris, who dubs Hagel ``poster boy for conflict of interest,'' says the Republican did not disclose the extent of his American Information Systems involvement and questions whether a former executive of a company whose machines count votes in precincts nationwide should run for public office. Hagel's staff insist that his former career doesn't affect his political life.

    ``I don't know if it's sloppy research or she doesn't care,'' Linehan said. ``I don't spend a lot of time worrying about it because it's all so ridiculous.''

    Criticism, as well as legal threats from ES&S, Diebold and other companies, has enervated Harris, whose blond hair turned completely gray last year. But legions of fans -- from New Zealand bloggers to respected computer scientists -- encourage her.

    Exploiting the power of the Internet, Harris has created a Web site that documents hundreds of local, county and state elections that have been botched or contested because of flaws with voting software.

    She details an incestuous web of voting company executives, politicians and election officials -- people who are often

  10. Problems on a more fundamental level by BelugaParty · · Score: 5, Insightful

    I can sit in a college library and browse people's laptops as if they are on a trusted network. People don't realize how public WiFi is in these environments. I think the main cause for this is the connection wizard (microsoft specifically). When you first connect the computer for wireless access it automagically, without a lot of warning, shares folders, printers ... etc, because it is assuming you are at your house with your linksys router; not at the library, coffee shop, or hijacking i-net from an apartment complex across the street.

    1. Re:Problems on a more fundamental level by JUSTONEMORELATTE · · Score: 2, Funny

      I can sit in a college library and browse people's laptops as if they are on a trusted network.

      Cool!
      So, what kind of MP3 collection does the average college student have on their laptop these days? This "library" you speak of sounds like iTunes, but without the credit-card part!

      --

    2. Re:Problems on a more fundamental level by kfg · · Score: 1

      Shhhhhhhh! Quiet. You wouldn't want people to get the idea that "going to the library" is a valid strategy for an anonymous file sharing club, would you?

      KFG

  11. Quality by Detritus · · Score: 1

    I've often wondered about the quality of 802.11 hardware. I'm not used to anyone using microwave and cheap in the same sentence. All of the commercial S-band radios that I've worked with are very expensive gear. What corners are they cutting in the consumer-grade hardware?

    --
    Mea navis aericumbens anguillis abundat
    1. Re:Quality by Jeff+DeMaagd · · Score: 1

      What power levels? High power 802.11 gets expensive, up to $150 for a 200mW AP. Of course, that's nothing compared to commercial hardware that puts out orders of magnitute more power, and the recievers are probably a lot more sensitive as well. The best for 802.11 that I've seen is -90dB sensitivity, typical is I think -80dB.

      I think one advantage is rediculous mass production to drive the costs down.

  12. How to Lie with Statistics by Detritus · · Score: 1

    Cancer is a disease of (primarily) old age. Cancer rates increase when life expectancy increases. More people are living long enough to get cancer. Eating a healthy diet will result in increased rates of cancer.

    --
    Mea navis aericumbens anguillis abundat
  13. There could be a problem... by Cytlid · · Score: 2, Interesting

    Concerning the second article, 802.11a seemed pretty clever to use for the uplink. A mesh within a mesh. But isn't 802.11a unencrypted? What's to stop me from pulling over along the side of the road with my trusty 802.11a nic and sniffing cleartext (uplink) traffic? That's a lot of pop3 passwords, my friends.

    --
    FLR
    1. Re:There could be a problem... by ofdm · · Score: 1
      ... isn't 802.11a unencrypted ...
      No. 11a, 11b and 11g are physical layer (PHY) components of the 802.11 standard. The Medium Access Layer (MAC) which sits above the PHY layer is common (with very small differences) to all the PHY layers.

      Security is specified by 802.11i (ratified in the last week or so) and applies equally to both 11a, 11b, and 11g. Until recently, they all shared the same poor excuse for security - WEP or proprietary extensions such as Cisco's LEAP. In the future, they will all share (when firms implement it) the Robust Secure Network properties of 802.11i.

  14. use more power by max+born · · Score: 2, Informative

    Many of these problems can be easily solved with more power. The FCC has imposed severe power limitations on 802.11 of about 100-200mW per channel.

    If the FCC would allow us amatuers to use, say, half the power that cell phone companies do, we'd be able to Wi-Fi the whole country.

    Give us the tools and we'll finish job.

    1. Re:use more power by Naffer · · Score: 1

      No, I think the solution is manufacturing more electromagnetic spectrum!

    2. Re:use more power by Anonymous Coward · · Score: 0

      You can have more power, if you reduce the bandwidth. Otherwise you will lose in what really matters: bit/second/area...

    3. Re:use more power by ofdm · · Score: 3, Informative
      This is, unfortunately, a common misconception. Increasing the range of 11b means that the available bandwidth has to be shared more widely - meaning that each user gets less bandwidth, which is to say data throughput.

      Imagine if you will, a world where you could hear everyone talking within a block of you. Sounds great - you can hear your stereo from a mile away (well, this already happens). Unfortunately you can also hear everyone elses stereo, and everyone else talking, and their refrigerators humming, and their dogs barking. The net result is that you can't hear anything clearly. It's very much the same as being in a very full pub towards the end of a horse race - everyone's making a tonne of noise, and you can't understand much of it at all.

      The solution is to have smaller cells, in the limit pico-cells, where an individual user gets the full channel to herself, and 10m away another user gets their own full channel. An alternative is to have large cells, but with APs having different non-overlapping frequencies - so that the cells are isolated in the same manner as for the pico-cells. Sadly, the lack of spectrum for 11b at 2.4Ghz makes this second solution unrealistic.

    4. Re:use more power by max+born · · Score: 2, Informative

      Yes, but with 802.11g and 802.16 the specs allow for up to 50+Mbps, several T1s. For surfing the net and reading email this is enough to supprort more users than may be commonly found in the limited area covered by the current power restrictions.

      The 802.X specs cleverly implement CSMA/CA, a collision avoidance system that seems to work pretty well. From my rooftop (downtown San Francisco), I can see 150+ networks yet never experience any symptoms of interference.

      Also, in setting the 802.11 limits on power the FCC seems to have overlooked the "skin depth" wavelength/2*pi attenuation factor that limits microwave ranges by a factor exponetially greater than for the longer wavelengths of many cell phones.

      I operate a couple of nodes as part of the sflan project and it would be nice if we could reduce the "line of sight" requirement just a tad by boosting the power, say from 200mW to 800mW.

      It just ain't fair than big bucks phone comapanies can "buy" an FCC license and blast away at 1500W while us folks trying to provide a free community service have to operate with our hands tied.

    5. Re:use more power by ofdm · · Score: 3, Interesting
      I ... never experience any symptoms of interference
      That's most likely because, as you said, your traffic requirements are low, and possibly the traffic on the newtworks you can see isn't particularly heavy. If you have access to the PHY layer, you will see that collisions are in fact very common. The standard provides a couple of ways for dealing with this. (I'm sorry if I'm teaching you how to suck eggs here - I don't know what you know, so I'm aiming low).

      At the base level, each data packet is acknowledged by the recipient. If it isn't acknowledged (an ACK) then the packet is re-sent. Depending on the particular manufacturers implementation, the retries continue, and if still unsuccessful, at some point the rate is dropped (the lower rates are more robust). Eventually, if there's no acknowledgement, the packet is dropped.

      At the higher level the MAC can take advantage of RTS/CTS. In this mode, before sending a data packet, a small "Request to Send" packet is transmitted - telling all the radios in range that it is about to send a packet and it will take such and such a length of time to do it - so please stay off the air. The recipient (the STA to whom the eventual data packet is addressed) responds with CTS - Clear-to-Send. Then the data transfer goes ahead. The RTS/CTS mechanism is designed to reduce collisions in heavily loaded networks. Unfortunately, it relies on all the radios which can make noise being able to hear and succesfully demod the RTS/CTS. Adjacent channels have the annoying property that they are load and interfere with you, but they are also incomprehensible. As a result RTS/CTS doesn't help with one of the more common mechanisms for collisions.

      In summary, collisions do happen, and adjacent cells/frequencies do lower throughput. Many users never notice this because of their low data requirements. As many posters have noted, even 1Mbps is more than most people need at present. However, as requirements go up (streaming video etc), this will become a much more visible problem.

    6. Re:use more power by max+born · · Score: 1

      No, you're quite right. I agree. I guess my point of contention is with the FCC. IMHO local communties should decide on power limitations. So for a small town with a few users over a large area it may be more beneficial to use higher powered trancievers than for a densely populated city. But local municipalities should be able to make decisions about how much interference is acceptable through their own elected representatives.

      The FCC's one-size-fits-all model is hindering WiFi's expansion.

      BTW, in the O'Reilly 802.11 book a suggestion is made about speeding things up by disabling the RTS/CTS mechanism and allowing the CA system to handle contention. I guess, as always, experimentation is the key.

    7. Re:use more power by wolrahnaes · · Score: 1

      I think that the regulations are just fine for omnidirectional installations. However if I am using a pair of old dishes for a point-to-point link, I should be able to use as much power as I can without nuking animals that stray in to the path of the beam.

      --
      I used to get high on life, but I developed a tolerance. Now I need something stronger.
  15. Pushing Wi Fi Limits by fegriffin · · Score: 3, Insightful

    Although there is never enough bandwidth, until we can solve the last mile bottleneck, 11Mbs 802.11b networks will be sufficient. With ADSL and cablemodem rates at less than 1Mbs that is where the problem needs to be solved.

    1. Re:Pushing Wi Fi Limits by RichMan · · Score: 1

      802.11b/11Mbs is fine for surfing the net. 11b will run into problems as the density increases.

      The next generation wireless is media access. Your TVs talking to the digital cable modem, the digital recording/storage devices, and satellite receiver without cables, distributing the HDTV signals from all your possible sources to all your possible end user devices/displays.

      That is what the next gen wireless is all about. The range needs to be big enough to cover your house but small enough that neighbors do not interfere. IE enough channel to share cells over a block or 1/2 block.

      I am in small part the buisness but not any one of the named players.

  16. Use directional antennas by KC7YRN · · Score: 2, Informative

    There's a problem, though, with using more power. You increase interference with everybody else while making a small improvement with your intended recipient. A directional antenna helps you when you receive as well as when you transmit. If you need to serve an area, you can still benefit from an antenna that concentrates radiation in a pancake shape so you don't waste power transmitting straight up. High power conflicts with sharing.

  17. Wi Fi meshes help protect file sharers by microbrewer · · Score: 2, Funny
    The good thing about mesh networks and leaving things unsecured is that you can fileshare without much worry from the RIAA becuse you can always claim that it wasnt you downloading from a IP it was someone hooking into your wireless router .Justin Frankel the godfather of distributed P2P file sharing has also sugested that it should be done on his own blog .
    May 19, 2004 I've been saying this for a long time, well over a year now: http://www.salon.com/tech/feature/2004/05/18/safe_ and_insecure/index.html
    1. Re:Wi Fi meshes help protect file sharers by tedric · · Score: 1

      Actually no, according to an article by the heise lawyer in the recent issue (sorry, no links, I only have the printed version) of German computer magazine c't - it may be different in other countries.

      If somebody shares illegal data using your access point whithout your knowledge and the police stops by it's your responsibility to show them that it wasn't you sharing all these warez, kiddie porn and MP3s. So if you plan on making your AP a hotspot, you should really think about how to create detailed log files of all the traffic going through.

  18. More power and more frequencies needed by DRWHOISME · · Score: 1

    That would solve all the problems.

    Think about all the radio stations on the radio dial and how much more efficient we could use 'our'(public) spectrum if we used wifi or even some variant like directional wifi(pringle can).

    I think only the government is impeding this.

    The radio spectrum is not used wisely.

    Lets change it. Time to get rid of 'radio'.

    1. Re:More power and more frequencies needed by nmos · · Score: 1

      Unless I'm missing something the entire AM & FM spectrum is only about 1/3 of what is already used for 802.11b/g. In other words enough for 1 more non-overlapping channel. I don't think that's enough to solve anything.

    2. Re:More power and more frequencies needed by DRWHOISME · · Score: 1

      http://www.ntia.doc.gov/osmhome/allochrt.pdf

      http://www.ntia.doc.gov/osmhome/roosa2.html

      military and gov use a ton.

  19. Will Smith? by darkain · · Score: 1, Funny

    I just hope that BelAir isn'r ran by The Fresh Prince of BelAir

  20. mo3 up by Anonymous Coward · · Score: -1, Offtopic

    not anymore. It's the problems clear she couldn't like I should be Slings are limited, FreeBSD had long though, I have to your own towel in suBrvival prospects

  21. Wireless Forums? by funklord9 · · Score: 1

    I've recently been having trouble with some wireless hardware. After exhausting the hardware manufacturer's support options, I looked for general wireless support forums, and didn't seem to find very many. Can anyone recommend a good place to get support for wireless hardware?

  22. WiFi good buddy by Anonymous Coward · · Score: 0

    When I can't get online I stand up and yell "breaker break"

    Wifi can't scale itself out of a paper bag..

    CB radio in a party dress, C/mon.

  23. gn44 by Anonymous Coward · · Score: -1, Offtopic

    one common goal - she had no fear BOUGHT THE FARm... unpleasant rivalry, and we''l of the GNAA I Mr. Raymond's contributed code lesson and Rules to follow

  24. Clue Stick by trolman · · Score: 1
    Ignorance is bliss. Now try to learn something.

    A Microwave oven works by transmitting the resonate frequency of water "Your microwave oven operates at a frequency of 2.45 GHz (gigahertz)" This is also the center frequency of 802.11 transmitters.

    The human body is mostly made of the water that this frequency resonates.

    1. Re:Clue Stick by Mr2cents · · Score: 1

      I didn't think the frequency is a resonance frequency. There's a whole band of frequencies that gets absorbed by water, there's nothing special about 2.45GHz. (that's why radio communications are so difficult from a sub).

      I bet I can cook you with a 1GHz signal.

      --
      "It's too bad that stupidity isn't painful." - Anton LaVey
    2. Re:Clue Stick by Rich0 · · Score: 1

      Like any substance, water absorbs energy most effectively at particular frequencies. There is certainly more than one peak in the absorbance spectrum (corresponding to various vibrational modes of the water molecule), and these peaks are probably reasonably broad - so microwave energy not exactly at the peak should work fine.

      Think of water as if it were blue tinted glass. If you shine blue light on blue tinted glass it will get a little warmer, but not nearly as warm as it gets if you shine red light on it. This is because blue glass is mostly transparent to blue light (hence the reason it appears blue). The same applies to water - microwaves at particular frequencies far from any peaks in the water microwave absorbance spectrum would cause very little heating of water. It would probably cause more damage to the microwave.

      My guess is that the frequency used in a microwave is a compromise between the absorbtion maxima of water, other common food products such as fat and protein, and engineering concerns.

      FYI - I am a chemist, and electromagnetic absorbance spectra are something that we consider fairly important - usually for the purpose of identifying and quantifying substances. Microwave absorbance is one of the less common forms of spectroscopy (Raman, I believe), but I believe it is closely related to infra-red absorbtion, which is more commonly used.

  25. Different kinds of radiation by AnotherScratchMonkey · · Score: 1

    It's important to consider the frequency. Ionizing radiation does permanent cellular damage. That's why it's cumulative. Microwave radiation is thermal. Claiming it would cause cancer over time is like claiming that holding a warm wash cloth to your head would cause cancer.

  26. wireless ALREADY has great range by thegoogler · · Score: 1

    i'm using my neighbors wireless right now and i dont mean nextdoor, he lives 4 blocks away! the signal usually doesnt cut out that much but when it does then everything i'm sending get curup!#KJH!KJ#H!BNMSDUIAYHKJ as i was saying everything gets curupted, but at least i get free broadband(w00t i'm gonna bittorrent all night)

  27. Except... by Gordonjcp · · Score: 1

    ... mice are nothing like humans. A mouse's whole body is about the size of half a wavelength at 2.4GHz. You can block a wifi signal with your hand. If we assume that RF penetrates wet squashy flesh to a depth of about 1", the RF will penetrate right through the mouse's body. It will, however, only reach a little way into the human body.

    1. Re:Except... by Tassach · · Score: 1
      So, substitute chimps for mice. Or, if you don't want to piss off the animal rights wackjobs, use lawyers instead.

      Even if you do plan to test on larger animals later, it's a good ideal to do your first round of experiments with mice simply due to the cost factor. Once you've gotten your initial set of data, you can repeat the experiment with pigs or chimps, both of which are much closer to humans in in size and physiology.

      --
      Why is it that the proponents of "one nation under God" are so eager to get rid of "liberty and justice for all"?
  28. 10 Watt Data / Voice Radio (ICOM ID-1) & Repea by ivi · · Score: 1

    Google for ICOM ID-1 for manual & spec's...

    In short: 128 kb/sec, has USB & 10BaseT cables,
    as well as a microphone! Does Data at that speed
    but also Digital Voice at 4.8 kb/sec & Analog Voice, all on 1.2 GHz (an Amateur Band)

    12 V @ 6 A on higher power, but reportedly more
    reliable than traditional WiFi gear, in cars, etc.

    Oh, it would require a Ham Radio License...

  29. Clue Boomerang by bill_mcgonigle · · Score: 1

    Ignorance is bliss. Now try to learn something.

    Wow, if you're going to be snarky at least get your facts straight.

    You're right about the frequency of the microwave oven, but it's not the resonance frequency of water, that's 545GHz.

    Microwaves work by electromagnetically vibrating any asymetrical (polar) molecules found in the target foodstuffs. Water is usually a very large percentage of that, but you're just vibrating the molecule, not causing it to resonate. If you did, the water on the outside of the food would absorb all the energy and you'd have a cold center.

    Some links:
    Microwave tech
    Good Eats
    Water resonance chart
    How Things Work

    --
    My God, it's Full of Source!
    OUTSIDE_IP=$(dig +short my.ip @outsideip.net)
    1. Re:Clue Boomerang by trolman · · Score: 1

      So the frequency used by 802.11 is 2.45MHz and cooks food deep down to the center? Now aim that amplified Yagi at your head and get a clue.