Slashdot Mirror
WiFi Bridging?
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!"
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.
Smoke signals
Just gotta figure out how to transform them into bits!
Monstar L
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.
In fact, there are other devices that could make this even easier. I saw that Linksys will be comming out with what may be the perfect product 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.
Comment forecast: Bits of genius surrounded by a sea of mediocrity.
What about using a directional antenna? The cantenna 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?
I was having an issue where the connection was dropping about every 20 minutes due to heavy interference. I tried 3 different WiFi cards, and 2 wireless routers before I came up with a simple solution.
Step 1: Locate ethernet port on the back of your wireless router
Step 2: Plug one end of a 50' CAT6 cable into it (or whatever your desired length is)
Step 3: Plug the other end of the cable into your NIC card
Remember, WiFi isn't useful for everything.
> 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 headset with a tinfoil parabola aimed out the window. At the other end was the base set and another parabola. We could do 300 baud to the mainframe.
You can get this done as long as you can get the antenna out from behind the metal wall and pointed across the street. Do your homework and get started.
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.
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.
Telcos have alot of dark fibre in the States. Most people assume that's optical fibre...but it's actually moral fibre.
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 enough cash to buy a decent used car.
I don't want free as in beer. I just want free beer.
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 assuming that it is correct. Any chance there is something else going wrong like another nearby AP using the same SSID or maybe your client is set to just connect to the strongest nearby AP and it is "bouncing" between the two? If you're using a fixed address instead of DHCP are you SURE noone else is using the same address?
Also as another poster mentioned, RG58 really isn't suitable for 2.4GHz, LMR400 is pretty much the standard for 5-50 foot runs.
What kind of antenna are you using? I know you said it's a 14dB antenna but is it a pannel, omni or what?
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.
l g/448
Here's the link:
http://www.oreillynet.com/cs/weblog/view/w
There are 01 types of people in this world. Those that understand binary, and me.
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.
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.
Bleh!
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 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
"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.
Kid-proof tablet..
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) and a new Linksys WRT54G. I had an existing WAP54G 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 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've actually got to put together a costings analysis for refitting our cisco kit next week. fancy giving me a hand with it, i like your style!
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...
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, firefighter, trucker, trucker wannabe). Another thing to consider is how close you are to a radio source (antenna, airport, publice safety facility, resistance cell, whatever). Again, I am not an expert at WiFi, but I have a lot of experience in trouble shooting and debugging, if you try and fix your problem without first determining it is not external to your setup, you may be just throwing money down a rathole.
This signiture copied from somewhere.
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.
E V E R Y T H I N G I W R I T E I S F A L S E
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.
R(k)
The real problem with Ethernet over smoke signals is when some bastard sends 0xFFFFFFFF and the blanket catches on fire.
- Give a man a fire and he's warm for a day, but set him on fire and he's warm for the rest of his life.
What with Gollum being after you all the time, my preciouss!
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.