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High-Speed Wireless LANs Move Forward 115

Posted by timothy from the network-zip-11215-anyone? dept.
GrokSoup writes: "Neat article from the WSJ (free site) about European hackers using 802.11 technology to create limited-range, high-speed outdoor networks. As you might expect, people are messing with directed antennas to send signals up to a kilometer. While I've tried this to get from the house to the pool, the idea of banding together in open-source fashion had never really occurred to me. Nifty!" We've mentioned consume.net before, but this piece mentions some interesting possibilities, like how the same idea may result in an approved-by-the-Man wireless network in Sweden, and the golden hope that multiple connection methods will let us switch handily among several wireless protocols as the occasion merits.
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High-Speed Wireless LANS Move Forward More

High-Speed Wireless LANS Move Forward

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  • wireless wan in australia (Score:1)

    by Anonymous Coward
    Checkout Australia's effort on the same front.. www.air.net.au sp78
  • My dream is to be able to sit on the quad with a laptop and work on my online HW, yet be able to watch people play frisbee... Hopefully before i graduate...


    mov ax, 13h
    int 10h
  • YES! I want one too. I'll pay $50 for one!
  • why not modex? Or are you writing a 90-degree-rotated Wolfenstein clone (and who isn't)?
    ---
  • I'll be able to telnet into my toaster and hack into other people's refrigerators late at night to see what there is to eat.


  • I've heard about these kind of free wireless networks before, and it sounds pretty cool. One thing I don't understand is this: how do these wireless nets connect to the mainstream internet? More specifically, who pays for the link?

    I have a always-on connection, but my ISP would crucify me on the telephone pole outside my house if I started routing random wireless user's packets through their network.

    For an experimental setup, there are plenty of universities and the like willing to donate bandwidth. I don't see this scaling, though.
  • Wireless LANS are still not suited for real use. They can be eavesdropped. Apart from that, there are stories where the someone from across the street (with it's own wlan) logs in on the network in a building on the other side of the street (which was supposed to be high-security). They could see all domains etc etc.
    The case I remember was where some computer-magazine was testing wlans and they saw the entire domains of the hospital (or some other medical facility) on the other side of the street..
    I'm staying aways from these things...
    Plus I think there's enough waves going thru my head already..
  • my ISP would crucify me on the telephone pole outside my house

    That is right on par with high-school-dropout-sysadminning-for-pot-money comment I read earlier to-day. Thank you, good sir, for your most enter-taining witicisms. Right-O.
    ---

  • Anyone else near Clapham Junction fancy joining together to do this? I have a WLAN in my office.
  • That is the funniest sig I've seen!
  • I would but that would mean using Java.
    ---
  • Most WLANs support 40 and 128bit encryption. Eavesdropping is irrelevant. Unless you happen to be listening with your own quantum computer.

  • Finland has wavelan ISP's (Score:5)

    by nchip ( 28683 ) on Sunday November 26, 2000 @11:40PM (#599376) Homepage
    Here at Finland, radionet [radionet.fi] and Saunalahti [saunalahti.fi] are busy building wavelan network. While the idea is great, at the moment they have many techincal problems.

    In practice you need a line of sight and radio frequency is used by many other devices. A common joke is to call it instead of a "wireless Network" a "connectionless network". Still those few who have managed to get a subscription seem to be more than happy.

  • you are kerrrayzee man.
  • well I suppose every luser with a linux box on the wireless network could route a little bit of the traffic through their cable connection. And seeing you are using IP Masq there's really no way the cable company could figure it out. With enough intelligent routing the system could approach an almost completely wireless net with the ISP's just doing the backbone movement between local wireless WANs. Although the wireless connections would want to get a lot faster. Ping times of 2.2ms for each jump is pretty slow.

  • Uh Oh (Score:3)

    by max99ted ( 192208 ) on Sunday November 26, 2000 @11:43PM (#599379)

    Julian Priest is walking east down Clink Street away from his office. He's holding his laptop in both hands and surfing the Web as he goes through an enviable five-megabits-per-second link to his desktop computer.

    I can see the headlines....

    LONDON - Chalk two more victims for Clink Street. In a continuing display of brutal idiocy, two men were killed earlier today when they inadvertently stumbled onto the busy thoroughfare. Ralph Foster, of York, was "surfing the web" on his new laptop while out for his lunch time stroll. Witness say he had just logged on to Hotmail.com and was happily deleting spam when he tripped near the curb and tumbled out headfirst into traffic. Police say he was killed almost instantly - managing, however, to log out before logging off.

    Simon Edwin, of Chester, had a slightly different fate. With two Palm V's in each hand, Simon was actually playing a modified version of pong online - against himself! The police cannot confirm his exact cause of death, saying only that they have yet to find the 2nd PalmPilot.

    These unfortunate events come just days after the loss of the entire development team from WebSolutions.com, who met untimely deaths when their Internet-connected coach flipped four times after the driver veered to avoid packet loss...

  • The problem with this is, if you want to network with seven other computers you may need seven unidirectional antennas-- for continuous connection.

    the alternative is to setup programmable "antennaebots" that are on a predtermined schedule to re aim the antennae(s) from one computer to the next either in a cycle or to send a "yoo hoo over here" signal through narrowband dialup to tell the other computer you need to connect.

    I had considered this as a possible way to share mp3s that might be better than napster/gnutella in highly populated and geographically flat areas.

    Problem: part of the routing data would probably need to include geographical location making it EASIER to track you to your location. one answer may be crypto/steganography, but even then for it to work people would need to be able to identify files on your computer.

    even with the potential privacy snags the prospects of a network who's infrastructure is owned by the public not by megalithic corporations.

    only with a completely unownable system available can we hold on to what freedom we have on the currently propriatary network infrastructure.

  • Though - this would require using secure protocols - otherwise it would only make eavesdropping much easier... Go figure - stick up an antenna and there you go! Instant data on a stick! :)

    --
  • Well, I think it's worse that in the office I'm moving out of, I lost the wireless connection any time the elevator went by.

    Yeah, bad planning for placement of the base station, but I'm betting that they put the telco closet by the elevators for easy access to wiring all the floors together.

    -Nev

  • 1km?? (Score:3)

    by demon-cw ( 162676 ) on Sunday November 26, 2000 @11:52PM (#599383) Homepage
    Nice, to start with:-)

    Currently we have a 802.11 based system which can do up to 30km on a p-t-p link and 5 km in radius!!

    We're using a selfmade module for enhancing the signal on the receivers end and 1,8m parabol antennas.

  • ;jjjjj;;;;;;;j;fsf;;;orking ve;y well! (Score:3)

    by tulare ( 244053 ) on Monday November 27, 2000 @12:01AM (#599384) Journal
    ssss;;;;jjjjjjmeeeeing it outsid;;;;ow, ans I jove it!!! ;ometimes I get a little ;;ne nojse, which can be distracting, but over all it's just ;;;;;j jjjjj;l;jjsssssaaaajd jjjjj;l
    Of course, I wouldn't do anything confidential this way... would you?
  • ..and also Australias Xnet [x.net.au]
  • If someone could come up with a peer-to-peer bandwidth hopping scheme, this would actually be pretty cool.

    My guess is that the easiest way would be to build in some sort of GPS ability (so you know where you are in relation to your nearest land-node). Your packets hop from wireless node to wireless node until they hit the land-node. Same technique for receiving packets.

  • Re:Eavesdropping (Score:3)

    by ipl31 ( 252950 ) on Monday November 27, 2000 @12:15AM (#599387) Homepage
    I usually dont like to make "smart-ass" remarks, but apparently all your data is based on what you have "heard" and "read", how long ago did you read that magazine article? All 802.11b compliant devices being made today support WEP which a form of encryption used for wirless lan technology (note: some older 80211b cards do not have wep ala AIRONET (before cisco bought them). Also on the other hand here is something to think about with wireless links, you would put an unprotected computer on the net? Well then dont put one on a wireless link, use a vpn over the wireless if you feel insecure. But "stay away from these things" becuase of what you hear is not the way I live my life. Later
  • Sure it may sound like a good idea now, but what happens when yahoo decides it can use this free open network and eats up all the badwidth. Party lines have never been a good idea when a large number of people are involved (just look at cable-modems!).

  • Seattlewireless.net (Score:3)

    by ipl31 ( 252950 ) on Monday November 27, 2000 @12:22AM (#599389) Homepage
    Any one interested in this technology should check out Seattlewireless.net [seattlewireless.net] we are a group building a free wireless network in the seattle area. Along the same lines as consume and other projects, however our mission is not based on internet access, but to create a network unto its own based on 80211b technology. We plan to have internet gateways present on our network, however we would like to see a local/free/public wireless network that had its own web its own irc, quake servers etc... Check it out for more info.
  • Yup,

    i gotta agree with these guys. what your saying is just scaremongering. at the moment i am working on a wireless lan project and i know that the hardware offers 128b encryption.

    i *think* the story you are talking about is some "techN0 journalist" drove past Apple HQ with an iMac and a Airport connection, and "sniffed" the insecure net inside Apple.

    As the guy previous said, if you are scared use a VPN.
    Would you put a Windows box as a server?

    rgrds
    b-B-t
  • Don't you know that you can't post a Wiki link to Slashdot without it getting abused?

    Oh well, it should be funny to see how badly their site gets jacked up. I hope they made a backup.
  • IMHO, what is needed is a centralized directory of all efforts to set up free wLANs. People could see projects going in their neighborhood, or search for ones in cities they want to visit. That way a hotel could be booked close to a base station.
  • The problem is that there are only a few 802.11 bands (3, IIRC). My rooftop antenna is currently on order. But even without that, I've noticed that my in-home wireless LAN takes a hit when my fellow professor, who already has an antenna, does heavy things. We both take hits from people with wireless phones in the same band.

    With a wired Ethernet, if the load gets too heavy we just split the subnet. With my DSL line, if my neighbor gets DSL I don't suffer. But I really don't want my neighbors to get 802.11 installations, because then my performance will drop -- both in-home and (once the rooftop arrives and I drop DSL) to the Internet in general.

    This a fundamental problem with wireless. Highly directional antennas help, but it's expensive to narrow the beam to 1 house from a km away, and so our current installation has an omnidirectional antenna at the base.

  • Its backed up frequently for this reason, the person running the site has this in mind.
  • what equipment are you using?
  • Are there already hotels, restaurants, diners, malls, etc. offering inhouse wireless LAN as a service to their customers? Are there any Palm devices with built-in wireless LAN?
  • We already have this in my city (Perth, Western Australia)

    http://www.iinet.net.au/products/broadband/citys pan.html

    expensive though.
  • Can this be adapted for cell phones , to get bigger band width through cell networks ? just a idea , im not smart enough to explain it or know the implications
  • Heh, and then just imagine that ethernet started out as a wireless radio packet switching protocol on Hawai. Coax was considered an improvement... See: What is the internet [uky.edu]
    The Ethernet concept arose because a researcher from Xerox PARC spent a sabbatical period at the University of Hawaii and noticed that the random access radio system could be operated on a coaxial cable at data rates thousands of times faster than could be accomplished through the air.
    How about using glass fiber to the home instead? Maybe even use wired routers switches to get our packets on the fastest network?!? Then all get what we want and we can reserve the limited bandwidth for radio packets for applications that really need to be mobile, instead of as a nifty techie replacement for DSL.

    --

  • 80211b is wireless networking spec that uses the 2.4 gigahertz band. Cell phones use 900mhz, WAP is essentially trying to make up for the short commings of cell technology in this type of applicaiton, two diffrent ballgames. The implications that something like this may have on cell phones is that an 80211b device could use voice over ip which could be used as an alternative to cell phones, however the range and line of sight with 80211b is not as good as with cell technology. I think what I just said makes sense...
  • Actually 80211b supports end to end encryption up to 128bit (WEP, not to be confused with WAP).
  • Many Airports (Seattle airport being one of them) which have "Laptop Lane" a little store where you can rent netowork access by the minute have wireless access points. The funny thing is that the ones I have used in airports did not have a key setup, so you could sit in close proximity and use their connection with out paying for it:)
  • Does anyone know of a website that will take two places and graph if they have line of sight?
  • Easy solution: if you want a secure network, wireless may not be for you. Some of us want to play games and share files, and we don't need a secured line for that.

    And oh yeah, you can encrypt this stuff.

    --

  • Low Cost Wireless How-To (Score:2)

    by Anonymous Coward
    You'll find the Low Cost Wireless Network How-To [gbonline.com] to be very informative in setting up your own underground wireless network.
  • This sounds like packet radio to me, Aloha protocol anybody? (a derivative of X.25).

    Of course, packet radio is only 9600 bps :)

    Wouldn't it be cool if you could do this with broadband wireless though?

  • I need something that will lookup in topographical data.
  • Let's not be dramaticly and completly dispose off cellphones. I'll suggest to wait for UMTS.

    Besides, in Holland we have two networks: 900mhz and 1800mhz. Since 1800 isn't much less from 2400 I don't think it would make a difference.

    Mark [zwienenberg.com]
    "Only two things are infinite, the universe and human stupidity, and I'm not sure about the former."
  • Is the "selfmade module for enhancing the signal on the receivers end" open source?

    If so, pls post a link to technical docs :)

    nicholas
    http://squat.net/ascii [squat.net]
  • consume.net has a node database at http://consume.net/nodes/ which is a start though can be a bit clunky j
  • symbol make an 802.11 phone which we wanted one of j http://www.symbol.com/products/wireless/wireless_s p24_netvisionappli_d.html
  • Guerrilla.net [205.159.169.11] is a project thats been trying to do a similar thing.
    Not sure how far they've got, but the've got lots of technical info for anyone really interested.
  • consume is one project going in London. Similar projects are in san fran, seattle, etc. I mean a directory of all the individual projects and then maybe a DB of all the nodes. I mean ALL of them.
  • Sorry it's propertary and it's a little electronic device (no open source code here).
    But you can find further information under http://www.funklantechnik.de (in german).

  • SSH (Score:2)

    by redhog ( 15207 )
    Who do not use ssh anyway? This neither less, nor more, public than the Internet. It can be eavesdropped? Yes. So can my connection from France (where I live) to sweden (where my webserver, IRC-client and more or less everything but my physical body, lives). But any eavesdropper won't be able to _use_ the collected data for much, except as random-source :) That is, if he doesn't have a big numbercruncher and can break my ssh...
  • > Click here to win a free 66G tape drive

    As opposed to winning a tape drive that isn't free? Why would I want to do that? Surely I can just ... buy one.
  • ..what the hold-up is on this technology? Why can they not just bump us up a little on the frequency and let us connect from the cell towers that are already perched pretty much everywhere? I don't have any details myself, but checking my email on the cell phone doesn't seem to require much effort.

  • Peer to peer isn't part of the 802.11 protocol, however guys at the University of Hawaii are working on hacking the protocol to pass peer-to-peer packets from many low powered "POD" stations scattered across the Hawaiian forests. These pods collect weather data and digital pictures and send them back to the base station for processing. This is from a grant from DARPA to monitor and protect endangered species in Hawaii.

    More information about this can be found here http://www.botany.hawaii.edu/pods/ [hawaii.edu].

    Hacking the 802.11 protocol for peer-to-peer passing of packets is very useful in this situation because this alleviates the need for extremely powerful antennae to be setup and pointed to many sensor stations scattered across a forest. Instead the pods are all within reach of another and packets are passed back towards the home station. Nifty.

    Check out the pictures of these pods on the site. Each station is custom made to blend in to the surroundings, looking like a dead log, or a lava rock or something.

  • The problem is defining how the addressing and routing will work - every node will need to be running a routing protocol at least (something like RIP should be OK for a small network).

    The nodes which have a wired connection to the Internet should advertise a default route with a suitably low metric - as these routes float through the RIP network, the one that 'wins' at any node is the route that represents the fewest hops to the wired Internet connection.

    There are probably much slicker ways of doing this but they'd also be more complex to set up.

    Probably all the wired-to-wireless gateways will need to do NAT. They should also do IPSec for those nodes that don't have WEP type encryption.
  • A little more information.

    Some kids living near these areas in Hawaii are in remote areas without high speed internet connections. (Almost the rest of the Hawaiian state has both cable modem and DSL available.) This network may also allow those students to finally have high speed Internet access.

  • That's actually link layer encryption - end to end means host to host, e.g. IPSec transport mode.
  • And there's nothing special about it.
    I happen to work at an ISP, which does exactly the same (InWay [inway.cz]), i.e. building a wireless network from BreezeNet's with external antennas, which were designed for office-wide wireless LAN originally..
    It's pretty common alternative to expensive land leased lines from monopolistic Telcos here in Eastern Europe, these ISPs have 1000s of customers.

    BTW, it's not very wise to build such a network based on DSS (direct spread spectrum) devices (like WaveLan) where FHSS (frequency hopping spread spectrum) devices are also allowed in the same band -- FHSS always wins the interference duel with DSS, because DSS sends the same data still at the same frequency, while FHSS hops over all the band randomly.
    There's also a very cheap (some $250 for both ends) device from Siemens called Gigaset M-1000 Data or something like that. It's a serial port version of a wireless phone It just extends a serial port (V.24, 115200 bps) over cca 500m distance, with external antennas maybe even more.

  • we're using products from Lucent to connect our entire neighborhood to a fibre-connection. This gives every house in the neighborhood broadband access. The initial fee from the company who sells this service to us is about 200 USD (2000SEK) and then we pay about 25-30/month (250-300SEK) for the service - wireless broadband at 11Mbit/s.

    And yes - it's 802.11b.

    And yes - we are all operating at different subnets.

    And yes - I will have a Linux firewall to protect my LAN at home.

    :-)

  • Yes, the old days of running a BBS. Strange to make the association, perhaps. But think about it, there was a community effort, BBS sysops would often share information or even share FIDOnet feeds.

    Now, instead of explaining why I had to get a second line to someone: "Well, I'm running a BBS." (other person) "What's that? Is that something like AA?"... Now I get to explain an antenna: (o.p.) "Why do you have that big thing on your roof? Is that a Satalite?" (me) "No, it's for the community based underground LAN." (o.p.) "If it's underground, why the antenna on your roof? What's a LAN anyway, is that like a satalite TV?"

    Oh well, some things seem to change but essentially stay the same.
  • I have seen many grassroots level projects for wireless lan in US, but they never succeed. It would be nice if this can take off, but it seems that what pushes the limit of technology is lack of it. Thus in US where we have DSL and cable modem, most people are relaxed, where as in other countries where high speed link is rare and very expensive, people are getting creative to overcome their problems.
  • Is there web site, or IRC channel, or InternetBBS somewhere that intends to connect the different groups building these WLANs?

    Would anyone from Windsor, Ontario, Canada be interested in building such a network?

  • Simplest way to live with this is ssh tunnels. Unless you do that you are effectively broadcasting your usernames and passwords :-) -hph
  • Actually, the Aironet cards did support 40-bit WEP, but not at the full 11Mb rate.
    --
  • We have a wavelan 802.11b network at my village in northern Sweden aswell.
    At the present, I am satisfied with it, but time will show whether the latency will increase drastically with the number of users.

    However, it is still the most cost-effective way to connect all the stand-alone houses to the internet with some amount of speed.

    Considering that the available alternatives still are ISDN and modem, the radio-lan is a very nice solution. The only backside to it seems to be the cost of the hardware.

    B.t.w... is the 802.11b cards able to speak with other 802.11b cards from other manufacturers?
    Lucent/Nokia/Symbol/etc...
  • my ISP would crucify me on the telephone pole outside my house

    That reminds me of a part in A Case of Need by Micheal Crichton where one character is describing another (ill-tempered) character. He says something along the lines of... "I hear that he carries around a bag of nails and a hammer in case he ever gets the chance to crucify someone"
  • I'm interested, but I'm from Houston. What I'd really like to see is a page where these can be registered, on a more global scale (consumed.net might be global, I can't tell). Any way, it would be nice.
  • Yes. IEEE 802.11b is a standard that all manufacturers are (supposed) to adhere to. Check out The official 802.11b (WiFi) site [wi-fi.org] for a list of certified compatible hardware.
  • Just hope that the quad, or your pool, doesn't have a dozen 802.11 beams intersecting there. The beams may not interfere with each other, but your radio will have trouble hearing through them.
  • I've worked with a company that has implemented a 802.11 system that has a range of 6-10 miles. It's not that difficult. We are reselling it as an alternative to DSL because bell is so slow. If you really want the equipment, ydi.com carries everything you need to hook up your own wireless POP, for about $2000 (not counting tower costs).
  • Anyone else near Clapham Junction fancy joining together to do this? I have a WLAN in my office

    You really need to check out consume.net [consume.net]

  • haven't we seen this before? (Score:1)

    by Anonymous Coward
    Don't we see wireless work every where already? I mean right in our own us we have people who are probably doing more advanced things with wireless. www.gbpppr.org [gbppr.org]
  • Sure.. you got the money for the equipment and net connection?? I've been trying to get someone to do this for years.. well i hear that one ISP is doing this, and i know Wincom has some wireless stuff too. -b

  • Eavesdropping 802.11b is child's play (Score:3)

    by Nonesuch ( 90847 ) on Monday November 27, 2000 @07:37AM (#599438) Homepage Journal
    WEP crypto uses the same key to join the network as it does to encrypt traffic on the network. All users using any particular access point can see each other's traffic.

    There is 64/128 bit crypto, in each case 24 bits are taken for the node address, leaving 40/104 bits for encryption keys.

    Crypto is done using RC4, a system with known, exploitable weaknesses.

    No Wires Needed [nwn.com] offers cards with factory-installed public key encryption and Diffie-Hellman support, but they do not offer their cars in the USA.

  • The November issue had a good overview of current wireless 11Mbps products and their limitations.

    Available at http://www.networkmagazi ne. com/article/NMG20001106S0004 [networkmagazine.com].

  • Did you realize you may be breaking your country's laws? There's a regulation saying how much power, computed as EIRP (equivalent isotropic radiation power) you can use when transmitting in the public 2.4 GHz band. Here in Czech Republic it's 100 mW (22dBm), which is also the ETSI norm. I believe it's the same in Germany.
    The maximum power level is counted as equivalent of an ideal isotropic antenna, so if you transmit at say, 4 dBm, and add a 24 dBm antenna you are at 4+24 dBm, exceeding the maximum by almost 50% ! With 1.8m parabolle, you could be well over few Watts.
  • Not to sound snarky... but so what?

    Many people, for several years, have been using wireless LAN cards and doing links of up to 15 kilometers. Several companies even originally based their wireless bridge products on wireless lan cards + some kind of RTOS on a small board.

    I have 802.11 links working over 15Km........ it's *easy*. This is barely even a hack these days, and it's nothing new. I mean, oh my god! You put a different antennae on it, and the radiation pattern turns directional, increasing range! WOW! It's not like every hammie in the WORLD doesn't already know that...
  • My wavelan gold card most definately has a button for 'encryption' as well as some other stuff to do with only allowing other cards with several ID bits set the same to connect.

    Encryption is the key, though..

    *OLD* wlans people, had no other layering to provide security. New stuf most DEFINATLEY does.
  • Umm.
    Who said anything about IP? Many things in windows networkign are discovered by *broadcast*, and use *other* protocols... like ipx or netbeui.

    And by 'log-on' he probably meant he could simply see all their public shares; lots of older networks, especially windows ones, did not use any kind of client authentication.
  • Well, I guess anybody can use the same DSS chips as the big makers use (WaveLan, Arlan) and some Ethernet bridge chips to have a nice wireless Ethernet device..
  • www.waverider.com

    I can say from experience, these are *just fine* for gaming. I don't know where you get your 'the latency is high' figures... but if the appropriate radio mac layer is used, latency is basically no different than a wired network of equivalent throughput. Why would it be slower?

    The *tend* to be slightly higher in latency (measurable, but not noticeable), due to overhead in dealing with the rf medium.

  • You need do no such thing.

    You have to a) obey regulatoroy radiation requirements (dictates power and shape of radiation pattern allowed) and b) use the appropriate antennae.

    For instance: the yagi's we use to do some 10km links radiate a 30 degree wide pattern. This covers *quite a bit* of ground at 10km That means, yes, that a bunch of end users can share a single radio channel, and you only need one antennae each.

    This problem is fundamentally no different than cellular problems: it's all about frequency re-use. You use alternating polarizations, proper channel separation, and can quickly built a tower that has, say, yagis every 15 degrees around the outside, covering an entire circle, giving you some nice coverage.

    Privacy snages? The Internet is alreayd a public medium.. you can't control your packets once they leave your network.
    wireless network cards almost all have built in encryption now.
    Routing data does *not* need to hold your geographic location; it's very similar to ethernet.
  • This is an honest question...

    Do you know whether or not this violates the regulations?

    I know that we have easily done large links like this before, but never within the bounds of the regulations on the ISM bands... I'm sure Germany follows such regulations as well..

  • The protocol was 'aloha', and is used when you have hidden nodes.

    You can't do collision detection, and you can't do carrier sense. Only one central node is guaranteed to see everybody. So they have a system of requesting a slot, etc...

  • We use wireless WAN access in Reading, UK. We have a 3.6Ghz point-to-point link provided by Tele2. (www.tele2.co.uk) It's a small dish pointing through a window. Only presents a problem when the window cleaner hangs down in front of it! It's about half the cost of a leased line for the same speed.

    If you get this post, it worked again.
  • DSSS doesn't 'send the same data at the same frequency'. It spreads it over the entire band, constantly (as opposed to a narrow transmission hopping around in side the band).

    I think the answer has more to do with power levels confusing the dsss receivers.

    You are right about which one wins the war though...

  • Before you try adding directive antennas to you 802.11 box, I'd suggest checking if what you are trying to do is legal.

    The idea of adding a directive antenna to a system to get most gain and thus a longer transmit distance is sound. The problem is that you can also interfer with anyone else system who happens to fall along the axis of the directive antenna. This is why most countries regulate these systems on their EIRP, or effective radiated power and not their actual power. The difference between EIRP and power is that EIRP inlcudes the effect of the gain of the antenna. Thus if you use a more directive antenna than the manufacturer installed, you are almost certain to be illegal.

    D.


  • Shamelessly lifted from BAWUG [bawug.org]'s links [playanet.org] page, where there is lots of information about wireless hardware and software:

  • I understand the bit about the frequency they operate on, however what I was saying is that WAP is aimed at cell technology where you dont have fast connection nor alot of CPU. 80211b has fairly good bandwith and uses standard networking protocols therefor it has no use for WAP
  • In the United States, 2.4 is unlicensed, and power can be up to ABOUT 36Db (4 Watts). We are doing this at our ISP, in a very rural area, and will be able to bypass the local phone system- all wireless and fiber. Smerf Qwest!
  • Bool, for these frequencies you will use directional antena, and no you will not get a drop
    in the speed. Besides you need no licence for any bandwidth as long as its directional, for which 900Mhz + is. You will have to have a hub somewhere, where the writeless turns into internet.
  • Ok, there are 14 frequency ranges that equipment can use. Granted they overlap, but even if you take that into account there are still 7 distinct frequency ranges available for use. In my experience (I networked 12 different schools together) there are few problems that can't easily be overcome.

    Possibly you're on channel 1 and your neighbor is on channel 2? That right there would explain it - the channels overlap. Move yours to channel 10 (the more seperation the better but anything over 3 should work.) Note: this only applies if using a point-to-point connection or if there are several unrelated access-points available. (The frequency overlap is designed to allow for "roaming". Not used it your situation.)

    Do both you and your neighbor connect to the same access-point? If so that would also explain it. Remember this is a shared 11Mb (ok, really about 4-6) connection. Kind of like a cable modem - other people using it will slow you down.

    One thing about access points is that everyone is supposed to be able to "see" each other - just like ethernet. If two clients connect to the same access point but can't see each other then they might both try to talk to the access point at the same time - not going to work. The solution here it to put your access point into a special mode ("ad-hoc" or something that sounds like that.) When in this mode, the access point will boroadcast a message telling all nodes to be quiet so the one node can send the message without being interupted. If this isn't done everything will appear to work great - even if under heavy load from one node. But under a heavy load from several nodes it will come grinding to a halt. A very hard problem to troubleshoot!!

    Now if this doesn't describe your situation then there are things you can do to solve the problem. For example, try rotating the polarity of both antennas (transmit/receive). This shoud issolate your system from the other allowing both to work, even if using the same frequency.

    Much of this depends on who designed and setup the wireless network. If they're new to it they'll have made some mistakes (speaking from experience.) Most techs thinks it's sooo easy to setup and use but neglect to consider some small, but important points. It's kind of like a web server. While it's not that hard to install Linux + Apache, it takes a little more to configure it as a production web server - just like there is more to setting up a wireless network then plugging in an access point.

    I'm going to cut this message short but rest assured, there are plenty of other ways to potentially solve your problem. If you give a more detailed description I might even be able to help out. My last employer really allowed me to really push the limits of 802.11. Now doesn't a 55km link to a mountain top sound like a cool project? Hmm, I liked that job. ;)

    Willy
  • In an improperly configured wireless network, yes it is possible to eavesdrop. But so can your home telephone line with an op-amp tool (the ones the bell guys carry). So can your cordless phone.

    When a wireless network is properly planned, there are 3, sometimes 4 or 5 layers of network security:

    1. In freqency hopping systems, there are 78 hopping patterns. Only one will "sniff" the packets in the correct order.

    2. ESSID. This is the network security password. Access Points will only respond to radios with correct ESSIDs.

    3. WEP. Wireless Equivelency Protocol. This is 40, 56 or 128 bit encryption that encrypts all communication on the radio.

    4. Direct AP connection to router/firewall. This stops any extraneous traffic from flowing over the WLAN.

    5. VPN Encryption. Many ISPs are using VPN from customer premise gear to the router, which makes sniffing wireless more difficult than wireline, since there are 4 extra layers of security.

    ---

    No security will ever be perfect, but then again, most people using wireless lans are using them for internet access which is inherently PUBLIC anyways.

  • When organized properly, wireless lans are NOT like party lines.

    It is possible to plan a network to maximize bandwidth to the customer without getting into cable-modem style problems.

    Look at the cellular carriers - they usually have less than 10MHz of bandwidth in any given area, but use time division and code division to make sure every phone has enough bandwidth for the call..... they aren't perfect, but their call drop rate is less than 1/1000 on average now.
  • Very easy to implement. Wavelan stuff has built in Point to Point ability. I actually did this when working for a school district. I put an old 486 box with 2 wavelan cards on a mountaintop (486 is more reliable - no fans - less heat - cheap - don't need performance.) Several schools (that were not in direct line of sight of each other) connected to the box. Running Linux, it acted as a simple router forwarding the IP. I then configured a Linux router at each school to route IP through the wireless network. No real IPs were lost - the wireless network used private IPs. The Linux boxes at each school just implemented IP bridging.

    Up in northern Canada, this was the _only_ way to connect some of the schools. Modems wouldn't work in several places due to the fact TELUS still uses some radio links. Hell, my parents can't get anything over 300baud on their 28.8 modem.

    I should also mention that with the right amp and antenna, a 55km link is very reliable - even in a snow storm. ;)

    Willy

  • Re:Eavesdropping (Score:3)

    by GC ( 19160 ) on Monday November 27, 2000 @11:50AM (#599462)
    We've implemented a Wireless link with Encryption to connect multiple sites. I have to say that I'm impressed with the performance.

    To join the network you have to be a registered device on that network.

    To eavesdrop you have to break the encryption key.

    The alternative to wireless was to implement a fibre link, but it seems to me that it would be easier for someone to dig into the ground and plant a device on the fibre much easier than attempting to break the encryption keys on a wireless link.

    Note this:

    With our wireless link there are a fair few checksum errors on packets, resulting in the odd retry request from the other node. I presume that these errors would not be known unless you knew the encryption keys, making it almost impossible to crack the keys as you cannot tell where the errors are without first knowing the keys. Has anyone done any research in random (deliberate) corruption to encrypted traffic in order to prevent key-cracking? Obviously this would come at a performance cost (extra re-transmit packets), but I guess this is to be expected for higher security.

    I'm sure anyone with enough spare time could probably break the keys, but probably not before we changed them.

  • Re:Eavesdropping (Score:3)

    by Zppr ( 22841 ) on Monday November 27, 2000 @12:54PM (#599464)
    Carnegie Mellon has a decent sized Wireless LAN [cmu.edu].

    To obtain a lease from the DHCP servers you have to be a registered [cmu.edu] device on the network.

    This approach seems to work well enough along with secured client applications (AFS, IMAP, etc via Kerberos [kclient]).
  • We run high ground (mountain top) Aironet BR500 repeaters/AccessPoints in the US which deliver about 30-31dBm of EIRP (well below the FCC max) into omni antennas and 4800 series radios with 24dBi dishes at the remote ends. We have stable links in the 16-18 mile range, and have tested out to 25miles. The hill tops have co-located high power transmitters on the sites (TV, FM, Cell Phone, paging, mobile radio repeaters, and the like) which contribute a significant amount of broadband noise to the site. As a result FHSS perform much worse than DSSS systems (which are able to recover signals below the noise floor). Our repeaters are therefor receiver noise limited, which limits our range even though we have the remote power tuned right to the FCC max on the dishes. In theory, this stuff can work out to the horizon (65-100 miles) if the environment around the site is RF clean (very remote) - and in dicussions with the military boys it does just that in certain areas. Even so, with three hill top repeaters we have better than 30% coverage of an area 40 miles wide and 55 miles long (just over 2,000 square miles under the antenna pattern, with an effective coverage area of just less than a 1,000 square miles after subtracting out shadowed areas). We will probably double that during the next year. Our market is NON-Wired high speed services, and we suggest potential customers that can get wired access do so. Some of our customers live off the grid - no wired power/phones - most do not have access to ISDN, DSL, Cable, or T-1's. We are a member owned, member-operated cooperative, with the goal of providing ourselves the service we need (when AT&T and Qwest cann't, or won't).

    We are a coop for a reason - it was clear from the beginning that you can only build out *ONE* of these wireless networks in a region. We allow equal access to our network by all regional ISP's that want to particpate for a $3K startup (includes radio/routers which are coop owned/managed) and $300/mo. In short, a turnkey service far less costly than the 2 man years and $25K it would take to rebuild the nework form scratch. Coop members pay $60/mo for service - about the same as DSL and Cable service in this area - and lot's cheaper than ISDN. We are not a free open source like entitiy ... but as a member-owned, member operated cooperative, the next best thing.

    Making it work more than a few miles without a 2500ft tower (aka mountain) is very difficult. Signal (wave front) diffraction is driven by pure physics ... and every object the signal passes bleeds energy off the wave front to fill in behind the object. So you lose 3-6dB over every building roof and tree that you barely clear with LOS. The diffracted wave front also reflects out of phase to distort the main wave front (multi-path) - creating a noisy/choppy signal.

    So flat landers with lots of buildings and trees, and no serious height, pretty much will have to live with short connections (under a mile or so), probably much less in typical city environments. This is much less a problem at 900mhz, is difficult at 2.4GHz, and a total killer at 5.7Ghz.

    While some vendors say that 2.4GHz isn't affected by weather, that is only partially true, and only for links that have 15-25dB or more of link margin. Many of our 2.4GHz links have less than 10dB of link margin, and see slight rain fade, but serious signal loss due to snow which causes serious diffraction problems coupled with broadband noise refection problems at the repeater sites (noise floor goes way up during snow storms). We manage this by dropping the modulation rate to 5.5mbps (doubles the power per bit) and decreasing the packet size (enabling fragmentation) to significantly reduce the probability of CRC errors due to noise functions. At 5.7GHz rain drops just completely eat the signal, and rain fade is really rain-block.

    Network performance with Hidden node operation, while managed by 802.11b, degrades rapidly underload. Aironet made a huge mistake when they failed to implement the Point Coordination Function called for in the 802.11 spec (PCF). In theory PCF can be used to stabilize the load curve, minimize load induced failures/overruns, which are a fact of life with hidden node architectures when using 802.11 devices in a wide area network.

    There is a lot of RF magic in making 2.4GHz 802.11 wide area networks work - the stuff is worse than plug-and-pray. It pretty much takes a $2-20K spectrum analyzer investment to debug problems. Even with that expect side by side experiments to have radically different results.

    Watchout for mixing FHSS and DSSS systems in the same area ... they do not mix well in weak signal applications. In close applications, the 802.11 spec requires them to check for energy in the channel and hold-off transmissions to minimize collisions. In wide area applications with all hidden nodes, they do not sense each other, and collisions rapidly degrade to inoperation.

    Or operation isn't perfect ... we do see brief periods of in-band interference, and high-power broadband interference which causes several second to several minute drop-outs in our service. Sometimes several per week, sometimes several per hour. But compared to unstable 19.2kbps dialup on rural phone lines ... it is completely heaven to get megabit web surfing with dedicated connections.
  • The November issue had a good overview of current wireless 11Mbps products and their limitations. Available at networkmagazine [networkmagazine.com]

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