Slashdot is powered by your submissions, so send in your scoop

 


Forgot your password?
Close
typodupeerror
×
Wireless Networking Hardware

WiFi Bridging? 51

Posted by Cliff from the wire-to-air-and-back-to-wire-again dept.
An anonymous reader asks: "I have a wireless network on one side of the street, and want to connect a computer on the other side of the street to it. Unfortunately this computer is behind a nice solid metal wall, and can't really be positioned near the signal. Currently I have a 20' USB cable going to a USB Linksys 802.11b unit, and a 20' RG58 cable going to a 14dB antenna and a PCI Linksys 802.11b card. Both of these cut out about once every 30 minutes, for about 5 seconds at a time. I also have an Airlink 802.11g PCI card and a Netgear 802.11b PCI card. What's the best way to connect to a kind of weak (-65db) signal? Can I use a wireless bridge in reverse, telling it an SSID and plugging the other end into an ethernet card? Which WiFi card has the most reliable software, that doesn't drop the connection all the time? I haven't been able to find much real info on this. Any help is appreciated, thanks!"
This discussion has been archived. No new comments can be posted.

WiFi Bridging? More

WiFi Bridging?

Comments Filter:

  • Linksys WET 11 (Score:1, Informative)

    by Anonymous Coward
    Get a linksys WET11. I'm currently using one for:

    airport -> wet-11 -> ethernet -> mp3 player+ airport -> tibook with crappy antenna.

    It's had one hiccup in the last 14 months that it's been up.

    • Or just get a Linksys WET. They're not quite as user-friendly as the DRY models, but you basically only get one (big) connection hiccup ever. Plus, you don't even need Internet access to use one to its full potential. Think of the money you'll save!
    • I tried one...but mine was extremely deaf. If I wasn't within 15 feet or so of the AP, it couldn't see it. Even with the device a few inches from an AP, it reported the signal as being weak. External antennae don't improve it either. I suspect there's something wrong with it.

  • Best form of wireless communication ever (Score:3, Funny)

    by antifoidulus ( 807088 ) on Friday November 12, 2004 @09:43PM (#10804338) Homepage Journal
    Smoke signals
    Just gotta figure out how to transform them into bits!

  • Firmware (Score:3, Informative)

    by Drew M. ( 5831 ) on Friday November 12, 2004 @09:53PM (#10804386) Homepage
    For starters, make sure the firmware on the routers is updated to the latest version if you experience dropouts. I had major dropout problems until I updated the Dlink access point I had. Also a signal level of -65db isn't bad at all if your noise level is around -100db. Right now I'm running at -72db with a noise level of -99db, but I've been all the way down to around -90db and have it remain useable. I'm shooting about 2 blocks over with line of sight.

  • Ethernet, not USB? (Score:4, Informative)

    by MBCook ( 132727 ) <foobarsoft@foobarsoft.com> on Friday November 12, 2004 @09:54PM (#10804394) Homepage
    I would try going with ethernet, not USB. The basic idea would be to mount a little ethernet to wireless device somewhere (and connect it to your antenna). If the thing can use Power over Ethernet (and you can supply that) then you'd only need one cable going to the device. By keeping the device near the antenna, you don't have the signal loss that your long antenna lead has. Something sort of like this [dlink.com] from D-Link [dlink.com].

    In fact, there are other devices that could make this even easier. I saw that Linksys [linksys.com] will be comming out with what may be the perfect product [linksys.com] for you.

    Now you should know that there are other (albiet more interesting) options. If you want to go for pure coolness and geekocity, I have just the thing. My brother managed to get a laser link for connecting networks between two buildings a few years ago. With think it's not functional (never tried, think parts might be missing), but it's a cool thing. We have two large units (look like outdoor security camera casings) that each have laser units in them. You point them at eachother, wire everything up, and voila! the networks are supposed to be connected. They were used at a local school years and years ago. Ours are probably slow, and we know they are tolken ring (that's about all we know) but they exist. You could probably find something similiar if you looked enough.

    As for your current problems, I don't know. I assume you are running Windows? If you were running Linux you could find out WHY the network is going down (watch for errors from the USB subsystem) but I don't know how (or if) you can do that in Windows. My guess is your 20' USB cable is part of the problem (just a hunch). Also, are you using directional antennas? Not just directional (in that they are not omni-directional) but HIGHLY directional antennas (like Yagis or the pringles WiFi antenna)? That might help too.

    Also, now that I think of it, I think many accesspoints have an option to bridge networks built in. A quick check says that my Netgear WG602v2 supports it. But it looks like both ends have to be operating in "bridge mode" (although you can still serve clients in bridge mode, it looks like). So that's a 3rd option.

    • We also had a laser link between two buildings for a few years and it was always embarassing to tell people that I could not answer emails because of fog.

      No to mention that my Y2K problem occurred because on the day before Y2K we had a hurricane which blew the one laser out of alignment which broke quite a few things.

  • Cantenna? (Score:3, Informative)

    by millisa ( 151093 ) on Friday November 12, 2004 @09:57PM (#10804414)
    What about using a directional antenna? The cantenna [cantenna.com] might get your signal over there better . . . Unfortunately, it doesn't appear to be sold with cookies anymore . . . You could also try one of the pringle can DYI antennas and see if it helps?

    • Re:Cantenna? (Score:3, Interesting)

      by sporktoast ( 246027 )

      If he's already got a long-ish USB cable, then the cantenna is not the best option. Cheap Asian [orcon.net.nz] cookware [slashdot.org] may do the trick. Though the Linksys USB device does not seem to be the preferred shape/size. The advantage is that USB cables don't suffer as greatly from signal loss as antenna cables do.
    • Pringles cans suck. They are a bad mix of two good designs - a stopped waveguide and a Yagi. What you end up with is neither a stopped waveguide *nor* a Yagi, and probably manages to be less effective than the pathetic internal antennas that wifi cards have.

      Build a proper stopped waveguide. I used a 100mm can, but it's a bit too big really to be resonant. You really want something about 85mm. I've set up a link to an Apple Airport base station over 500m with one, with the base station inside a sandsto

  • > What's the best way to connect to a kind of weak -65db) signal?

    Make it into a not quite as weak signal. Since you know exactly where your antennas will be, go directional at both ends. I don't have URL at my fingertips, but the web is loaded with instructions for building G band directional antennas.

    Way back in the wentbefore we set up a connection across about 1200 feet of open space between a VT-xxx terminal and a PDP 11. The terminal got an acoustic coupler and a Radio Shark cordless phone head

  • Replace the RG58 (Score:3, Interesting)

    by Bishop ( 4500 ) on Friday November 12, 2004 @10:03PM (#10804449)
    A good place to start would be to replace the RG58 which is a terrible cable for 2.4GHz. That said -65db is not a weak signal. -90db is a weak signal. It could be that you are saturating your recievers. Try lowering the power.
    • Not only is this coax a bad choice for microwaves [2.4 GHz] but it will probably not fix your problem much at all. Considering this wire is not designed for microwave, you will have considerable loss in the power emitted and would most likely be better off leaving the wireless transmitter near the computer and metal wall to begin with. USB tends to be lossy too but probably no where near the coax. If you can try to place the Access Point and/or Wireless card as high as possible in your location and across t
    • RG-58 will have terrible loss at 2.4 GHz. Try to get rid of the coax, and extend the USB cable if possible. If you HAVE to use coax, try some Belden 9913 coax. It is an air-dielectric RG-8 type coax that will still not be very good at 2.4 GHz, but it is cheap, easy to find, and will be a vast improvemment over RG-58. Draw-back - 9913 is a larger diameter cable - about a half inch outside diameter - and it is stiff, and hard to work with around corners. Tip: Make sure you order it with the type "N" con
    • Suprisingly, I've found RG-6 to work extremely well with 2.4Ghz, with only 18db of loss per 100ft

  • You want a client bridge (Score:4, Informative)

    by Gaewyn L Knight ( 16566 ) <vaewyn AT wwwrogue DOT com> on Friday November 12, 2004 @10:44PM (#10804640) Homepage Journal
    Tiny little boxes... connect via wireless to another AP and provide a single ethernet port out.

    Senao (Engenius Tech) makes 2 nice little boxes for doing this that have 200mw transmit and the best receive thresholds on the market. This puppies have NICE radios.

    You are looking for either the NL-2611 CB3 (802.11b) of the NL-3054 CB3 (802.11b/g and is also bi-mode [can operate as AP and client at same time])

    Just through a network cable in place... connect this... adn ditch that USB crud.

    • Re:You want a client bridge (Score:1, Informative)

      by Anonymous Coward
      agreed. In my old office we had the same situation: the only way to get broadbad was to run it from across the street, as Verizon would connect lines on that side of the block, but not ours. Our landlord occupied that building and was happy to let us run in a phone line and put a 802.11 DSL router on his window ledge, so that was our solution. Problem was about 60 feet and multiple steel-reinforced brick walls. Our soultion was the same offered by the parent post, except cheaper: we used a Netgear ME101 bri
  • It will cost some real money (about $3000 list I think), but the best way to do this is to get a pair of Cisco wireless bridges. Either the model 1300 or the model 1400 would be suitable. They can be mounted outdoors and are intended for bridging. If you really want to stick with your sub $100 solution that's fine; just remember that you'll get better quality when you buy quality hardware. It's also entirely possible that you can with a connection that cuts out every now and again if you'll end up saving en

    • Re:Cisco 1300 or 1400 (Score:4, Informative)

      by hbackert ( 45117 ) on Saturday November 13, 2004 @02:21AM (#10805478) Homepage

      just remember that you'll get better quality when you buy quality hardware.

      While I can generally confirm this, and I certainly like my Cisco AP, this is an overkill-solution-par-excellence. Of course you can go to work with a comfortable car and of course it's faster than a bicycle and of course it will be more expensive, but when your office is 1km away, this does not make any sense at all. Cisco bridges are great just like Cisco routers/switches etc., but I would not recomment anyone to buy a Cisco router/switch for private and small networks. It's just not worth it and most people cannot use nor do they need all those nice features. In a company, stay away from generic stuff with only web interfaces and get the good, expensive Cisco & Co stuff, but at home it's the opposite way.

      I had a similar problem (2 networks to be bridged, albeit shorter distance) and I did this:

      • Set the access point on once side of the network (that was the simple part)
      • Set a Soekris 4521 [soekris.com] with a CardBus WLAN card on the other network
      • Let the Soekris connect via WLAN card to AP
      • Bridge traffic between ath0 (the WLAN card) and eth0 (the onboard-LAN).
      • Use eth1 for connecting to the Soekris for management purposes, but I can easily live without it as it works reliably.
      Costs: I had the AP, I had the Soekris box, I had a PoE adapter, I had to buy a CardBus Linux supported WLAN card (Atheros) as I could not use the PCMCIA Prism card I had. Costs for me: 7000 Yen (approx. US$70). Costs for someone without all this stuff: about US$400 for all of it, which includes a Soekris board which is likely overkill for this one job. But it's very reuseable, so I could this as an investment.

      Another option was the purchase of a Ethernet-WLAN bridge (connects to an Ethernet port, has a small computer inside with WLAN on the other side, and it's simply bridging stuff from left to right and right to left, just like the Soekris does). Costs 9000 Yen here in Japan. But it only good for one Ethernet port (1 PC, not a network).

      Both beats paying US$3000 for a Cisco bridge set and the former is far more versatile while the latter is easiest to set up (if 1 PC is all you need). Setting up thr Soekris is dead-easy if you've ever set up Linux routing/bridging/WLAN, before.

    • And for less than $300 you can get a pair of Senao bridges with rockstar radios, and spend the other 2700 on hookers and coke. Or Compassion International, depending on how you get your kicks.
  • I have a wireless network on one side of the street, and want to connect a computer on the other side of the street to it. Unfortunately this computer is behind a nice solid metal wall, and can't really be positioned near the signal.

    Just some random thoughts:

    Well, how far away IS this computer from a location that would have good LOS to the wireless network? Do you have access to a laptop so you can do a sight survey in the area of your client?

    As others have mentioned, -65db is actually quite strong as
  • I don't know if it's applicable for your situation, but you have heard of the Pringle can antenna, haven't you? It's supposed to work really well, and it's been a while, so i'm sure there have been improvements made by others too.

    Here's the link:
    http://www.oreillynet.com/cs/weblog/view/wl g/448

  • One possibility I forgot to mention in my other reply is that your problem could be interference from some other 2.4GHz equipment such as a cordless phone. Using a laptop to test your conection in various locations between the two sites would probably help track this down. Then again, it could just be that every 30 minutes a (large metal) bus passes by on the street blocking the signal for a few seconds.

  • I just did something like this. (Score:3, Interesting)

    by crisco ( 4669 ) on Saturday November 13, 2004 @12:52AM (#10805183) Homepage
    Client wants to extend network to a shop enclosed in a metal building, primarily for internet access. Two Linksys bridges, one with its antenna sticking out a little holde in the side of the building and one inside. Set the bridges to different IP numbers and different frequencies (channels) and one wireless device, in my case a laptop computer, can connect. If more then one wireless device needed to connect in the shop I'd use an AP instead of just the bridge.

    As others have noted, using a USB cable and an antenna cable might be making things more difficult than you need. Try pushing power and ethernet as close as you can to the antennas so you can put the wireless devices with the antennas.

  • Cantennas and boosted transmit power (Score:3, Insightful)

    by Guspaz ( 556486 ) on Saturday November 13, 2004 @01:41AM (#10805330)
    Grab two Linksys routers or access points, the kind that allow third party firmware to boost transmit power. The WRT54G would do nicely.

    Then buy two Cantennas (http://www.cantenna.com/), and point them at eachother. You should have no problems getting a very strong signal.

  • A few suggestions (Score:4, Informative)

    by gtoomey ( 528943 ) on Saturday November 13, 2004 @02:13AM (#10805449)
    I've written a basic linux 802.11b wifi HOWTO [gregorytoomey.com] to help people with basic connectivity issues.

    A commercial 14dB antenna is high gain for wifi and should work for miles, so the dropouts you are experiencing are very strange. I suggest starting a packet sniffer like Ethereal and seeing what happens when dropouts occur.

    If you can use a standard outdoor wifi antenna (made by dlink etc) bolted to a bracket, commercial pigtail and limit the RG48 length you should have no problems. You can reduce cable length using power over ethernet.

    I'd put an access point at both ends (rather than wifi cards) as it will effectivelty do the bridging for you

  • You're only trying to go -across the street-? (Score:3, Funny)

    by adolf ( 21054 ) <flodadolf@gmail.com> on Saturday November 13, 2004 @03:11AM (#10805602) Journal
    "Across the street" means to me that you're only going a couple of hundred feet, at most, and that you've got a rather clear line of sight. With 20 feet of RG-58 and a 14dB antenna, your total antenna+feedline gain is something near 9dB.

    And 9dB of gain should sure as fuck get you across any street I've ever seen.

    Obviously, then, you're doing something wrong.

    And since you never mentioned it, I'll surmise it: Your antennas are all indoors, aren't they?

    Solution:

    Punch a hole in each wall[1]. If it's like most metal buildings, a regular twist bit in a drill will chomp through it in seconds. If it's thicker than that, you'll want to enlist the help of that friend of yours who already has an acetylene tank. If you don't have a friend like that, now is the perfect opportunity to recruit one.

    Once you get your holes, run your cabling through them. And then place both antennas outside.

    Yes, the USB adaptor should be outside, too. Use a butter tub (Wal-Mart, dairy section, ~$1.50) and whatever sort of fluid adhesive substance you find appropriate or happen to have on hand. Make a hole with a pen knife to poke the USB connector through.

    Done.

    [1]: If you cannot do this for political or aesthetic reason, just order DSL for the remote location, find yourself some comfortable VPN software, and stop wasting time trying to microwave things through grounded metal structures. Thank you.

    • but also consider once you've drilled the holes, how much easier/faster/more secure your life would be if you simply slung a length of cat5 between the two holes...

  • Linksys boxes (Score:3, Informative)

    by Gid1 ( 23642 ) <tom@@@gidden...net> on Saturday November 13, 2004 @07:46AM (#10806120)

    I just did something a bit like this. I live in an apartment in the same building as my office, but it's on the other side of the building. Minor detail: the building is L-shaped, and home and office are on the different branches.

    I spent a month or so going through different options: looking for a third point on the other side of the street that could act as a line-of-sight reflector, investigating existing cable ducts with phone wire and that long range ethernet thing.

    Finally I decided to get a directional antenna (this one [wirelesspro.co.uk]) and a new Linksys WRT54G [linksys.com]. I had an existing WAP54G [linksys.com] which I use for the other end.

    The WRT54G is in my hallway at the apartment, stuck to the wall above the entryphone. The WAP54G is in my office, with the antenna bolted to my office balcony. Using the Sveasoft [sveasoft.com] firmware, I've boosted the signal a little and have established a ~2Mbps bridged link by blasting the signal through the apartments in the line of sight. The WRT54G acts as a repeater for my laptop. Since the office only has a 2Mbps line, it's good enough. The people in the apartments between might start having funny-shaped babies, but I've got free connectivity, and that's all that matters!

    I'm sure it would be better if the home-side box had an external antenna, but it's intrusive enough in my hallway anyway. I'd also then be able to use the stock firmware. The Linksys boxes are relatively cheap and thanks to third-party firmware are extremely configurable.

    As far as the 5 second break every 30 minutes goes, I'd guess it's some third-party box negotiating something (eg. NetBIOS or NTP or something) and interfering with the signal on your cable runs.

  • I am not a WiFi expert, but it seems to me that all the experts so far have missed a rather large detail. If your signal cuts out on a regular or fairly regular schedule, then there might be something external to your setup that is causing the problem and would cause problems no matter the set-up. You said the signal crossed a street, maybe every half hour a car stops exactly in the path of your transmission - transmission interupted. Or perhaps a vehicle travels by with a powerful radio transmitter (cop
  • Given the troubles you're having and the frequent disconnects, I'd suspect something else on the 2.4ghz frequency is causing intereference.

    Lucky for you, 802.11a gear is very cheap (tons of surplus available inexpensively online) and operates in the 5ghz band.

    Buy two 802.11a bridges from some place that has a good return policy and see if it doesn't work for you.

  • Both of these cut out about once every 30 minutes, for about 5 seconds at a time.

    I've experienced this part of your problem, my router would drop every 30 minutes or so for a few seconds. The fix was to update the firmware on the router, you should try that if you still have the same problem.
  • Telex and Inscape Data both make Wireless ISP CPE bridges that are POE with integrated radios and directional antennas. Retail for about $320. Put two of those up and you have a extremely reliable link.

    A number of companies sell them.... Connectronics is a supplier I use.. They're a dealer but afaik they will retail sale parts as well.

Slashdot Top Deals

I have hardly ever known a mathematician who was capable of reasoning. -- Plato

Close