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Ask Slashdot: Overcoming Convention Hall Wi-Fi Interference?
bbowman writes "One of my job responsibilities is to set up the small network for our company's exhibit at the trade shows we attend. The mobile demo devices we use depend upon a reliable Wi-Fi connection to a router I have in the exhibit. In the days leading up to the opening of the trade show, W-iFi connections are reliable and work as expected. However, as soon as the show opens none of our devices can reliable maintain a Wi-Fi connection to the router. The devices we use at the trade shows are Windows-based laptops, iPods/iPads, Android tablets, and a variety of Wi-Fi enabled cell phones. I have tried using channels 1, 6, and 11 (as well as the others) and used different routers (Linksys, D-Link, Netgear) without success. I'm sure it is likely that there are poorly insulated electrical cabling, fluorescent lighting, and other issues that would contribute to Wi-Fi interference in the convention hall. A quick scan shows dozens and dozens of discoverable Wi-Fi networks nearby. If I take the router back to my hotel room, I have zero connection problems. How can I overcome this so that Wi-Fi works reliably in the convention hall?"
I'm sure everyone will understand.
Alternatively, install a giant metal Faraday cage. (Good luck with that.)
The World Wide Web is dying. Soon, we shall have only the Internet.
If your devices are 802.11n compatible, you could put your router in n only mode... The 5.4ghz band may be less crowded.
- Holy crap, I've got MOD points! Who thought that was a good idea.
For the devices that support it (decent laptops, iPad, and possibly other tablets), going to the 5 GHz band is a huge win. There are plenty of non-overlapping channels, and congestion is lower. The problem is that most WiFi enabled phones only support the 2.4 GHz band, so this will not cover all cases.
The problem is intrinsically a hard one, 802.11* wasn't really designed for a zillion flacks in a large room, each toting personal cell routers and whatnot.
However, it is possible that the problem could be solved by money. Let's just say that "(Linksys, D-Link, Netgear)" isn't exactly an honorable lineup of the finest names in Serious Wifi. Cheap, yes, quite delightfully so. Built right down to price? Well, you could say that...
You might want to do some looking into the world of "industrial wifi" products. The environmental resistance of such will be total overkill for a tradeshow floor; but (successful) offerings in that sector are designed for people who need their network to work despite the fact that it is in the middle of a factory floor or next to the arc welder or what have you.
The trouble with going upmarket, though, is that it can be somewhat hard to tell what is genuinely better at wireless networking vs. what is just the same old shit on the wireless side; but in a POE, ruggedized, -40/+135 thermal resistant, with baked-in proprietary management protocols in the firmware, container. You really want the former, not the latter...
Build your exhibit with a dungeon/prison them to hide the faraday cage that isolates you from the rest of the auditorium. Add lots of dry ice and flashing lights and not only will you have a working exhibit, it will look cool as well.
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FYI Steve Jobs routinely uses out of spec channels. For WWDC, this used to be channel 13, which is not licensed for use in the US, but is in Japan.
This got to be a problem (leading to the famous "you've got a choice..." speech) when enough Japanese Mac developers attended without changing their locale, and all the Japanese machines ended up on channel 13 because it was "less crowded" (for obvious reasons).
-- Terry
In the days leading up to the opening of the trade show, W-iFi connections are reliable and work as expected. However, as soon as the show opens none of our devices can reliable maintain a Wi-Fi connection to the router.
I doubt it's this:
I'm sure it is likely that there are poorly insulated electrical cabling, fluorescent lighting, and other issues that would contribute to Wi-Fi interference in the convention hall.
...and more likely this:
A quick scan shows dozens and dozens of discoverable Wi-Fi networks nearby.
I would recommend trying a few things:
- Reduce your RTS threshold, if your AP supports it.
- Reduce the fragmentation threshold, if your AP supports it.
- Play with data rates, reducing them if your AP supports it.
If your AP does not support any of those options, go out and get a real AP.
Never start vast projects with half-vast ideas.
Some Cisco and other high end access points have beamforming networks that can place antenna nulls in directions of interferes (other AP's, microwaves, etc) and point the peak of the beam directly at a user among all types of other fancy tricks.
They work wonderfully well in noisy, cluttered environments. Give them a shot.
http://www.cisco.com/en/US/prod/collateral/wireless/ps5678/ps10092/white_paper_c11-516389.html
My consulting business specializes in providing show management services to associations putting on large meetings. I work with Facilities to provide wifi zones, as well as information kiosks, and internet access kiosks for attendees. I recently did a large meeting in Chicago (30,000+) attendees. This presented many challenges but the biggest issue was on the exhibit floor where a site survey revealed 160 rouge access points on 2.4ghz. Not only was the building Wifi having troubles it was like the wild west among the exhibitors, most had to be within a few feet of their access points while some others used amplifiers or enterprise class APs to get the extra signal strength, if all exhibitors upgraded their signal strength everyone would be back to square one. I tried to alleviate the problem by setting up a secondary SSID on the building infrastructure for exhibitors with decent bandwidth and tried to encourage some of the exhibitors to use this instead of their own. I got the rouge access points down to 90, but certain areas of the exhibit floor where still flooded. This is an inherent problem with wifi that the more APs competing over the same radio frequencies the more noise and less throughput you will manage. Without a doubt the best solution is to move to another frequency, as I found very few were operating on 5ghz (802.11a), The real challenge is to make exhibitors and attendees aware of the shortcomings of this technology in an environment with so many users and competing APs.
Why not simply use a narrow-field directional antenna for your demo? If you're just feet away from it, it seems unlikely that other nearby networks would be strong enough to drown out the signal.
"Tell me doctor, with all of your defenses, are there any provisions for an attack by killer bees?"
Sounds like either forcing 801.11n only or using 801.11a is the only inter-operable alternative unless you can modify the devices and play with other parameters.
What about getting the convention hall organizers (or you and your nearby booths) to try and build a mesh, so everybody is on the same network (and can somehow tweak parameters to reduce interference)? Maybe coordinate the channels between nearby booths so they don't overlap? Not that there are than many channels to distribute.
Perhaps the router could be connected to a dish above the booth pointed straight down like a street light. This could overpower other signals in your booth and reduce your interference to other users. Dishes at wifi frequencies aren't large.
I used to set up networks for training and conferences my group did. We picked up an Extricom http://www.extricom.com/. I never had problems in the dozen times I used it. Its an interesting system, it has a central Wifi unit, and you run cat-5 out to 4 remote transmitters. You can place them spread out over the area. Admittedly the model I used, the Extricom ESX400 and 4 radios no longer seems to be available but check it out. -Joe
http://en.wikipedia.org/wiki/Nicolas_cage
Obi-Wan: "I felt a great disturbance in the Force, as if millions of voices suddenly cried out in terror and were sudden
Tom's Hardware did an excellent and extensive test on WiFi networks not long ago. It is well worth the read, as is the first part of the series. http://www.tomshardware.com/reviews/wi-fi-performance,2985.html
i work at a convention hall...are you sure they're not containing your AP? we don't allow outside managed gear although most people don't realize it until they can't connect to their router five feet away. we have our APs contain any rogue APs to avoid losing $$$ to folks showing up and trying to provide free wifi. most of the convention and exhibit centers we deal with do the same thing. the last thing we want is someone providing unsecure free wifi in the building and then we get blamed for 1) shitty bandwidth 2) mitm attacks 3) bad customer service because there's nothing wrong with our gear when you have an issue with dude in the next booth's cell phone tethered AP.
I have been setting up wired and wifi networks in trade shows for 10+ years now. :)
Welcome to wifi Hell
I do not think achieving 100% reliability is a sane goal in that context, but I found that there are simple ways to greatly improve the odds.
> Consumer-grade routers / AP are no good. They often do a fine job, and they always give up quickly.
In my view, using small-business equipment is a better way to go : still affordable, and a lot more resilient.
For about 400 $ you should be able to find a basic gateway and access point (new - I'm thinking sonicwall / netgear prosafe / hp pro curve...)
And if it matters, you still have web-based interfaces available to configure them.
> Use fixed ip when possible. Avoid encryption if you can, avoid wep if you can't.
> Reserve the network for your demo gear. If you also have to provide internet access to people working on the booth, use a separate network/gateway (your current linksys/d-link/... router might do the trick if less critical).
> Also : wired.
Not an option for your whole setup as I understand, but maybe part of it.
I am no sysadmin/network admin/whatever so this is basic stuff, but works for me on a regular basis in your exact predicament.
Hope this helps, and good luck to you.
You're running into the big problem with wifi: Everything on the same channel has to take turns. If there's 40 APs all in the same vicinity, they're going to start a round-robin game of who-goes-first, and if there's enough other interference, they're all going to keep yielding, and nobody gets heard. See "myth" #1 here: http://www.cisco.com/en/US/prod/collateral/wireless/ps9391/ps9393/ps9394/prod_white_paper0900aecd807395a9_ns736_Networking_Solutions_White_Paper.html As it mentions, this is more accurately called co-channel cooperation, rather than interference. And it's a huge problem in a convention. You're really kinda screwed in that scenario... unless you can use another spectrum, but it sounds like that's not much of an option given that you're trying to demo on consumer client hardware that's almost invariably 802.11b/g/n, 2.4ghz. Use A band if you can. Another thing you can try, and this would take some serious cooperation with other convention-goers (read:social engineering, perhaps?) is to get everyone to turn down the broadcast power on their APs. That's what the real problem is. If everyone talks quieter in the library, more people can carry on their conversations in their corner of the woods. You can also try to work out a pattern with nearby AP users to switch their APs to channels that don't overlap with yours. Be careful with this one, cause if you've got two APs on channels 1 and 4, they overlap enough it might still cause co-channel cooperation. This is probably pie-in-the-sky thinking that your fellow convention goers (and possible competitors even) might cooperate to that level, but there's no hurt in trying, right?
"For WWDC, this used to be channel 13, which is not licensed for use in the US, but is in Japan."
Does he have special WiFi firmware to go with it?
Channel 13 stops working on my MacBook if any access points with the country code set to 'US' are nearby, even though I'm clearly in Australia (where 13 is allowed).
Well sort of solved it. We were demo'ing a handheld wireless device that did not have a wired port. We opened the device, popped the nano sized connector from the wifi module to the PCB inverted "F" antenna and connected a very thin coax to the now vacant wifi module's antenna port. We connect all of the unit's coax leads to a RF mixer (think an analog version of a router) and also hooked up a generic wifi router via coax to the mixer so that the handheld units could talk to our on-site server (handheldmixerWiFi routerserver). Our demos worked perfectly. Nobody else had anything working and one of the main points of the show was to show off wifi capabilities. It took a bunch of cables and adapters/gender benders, etc as consumer routers have most of their pin's gender reversed so that you can't do this with retail parts and cables.
13 is allowed in Australia and Europe as well, but overlaps significantly with channel 11 and a few of the other higher channels.
There is a channel 14 that is only allowed in Japan and it is far enough above even channel 13 that there's virtually no overlap.
http://en.wikipedia.org/wiki/List_of_WLAN_channels
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RUN A CABLE
Great idea! Now where's the RJ45 jack on this here iPad again?
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