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Ask Slashdot: Overcoming Convention Hall Wi-Fi Interference?

timothy posted more than 3 years ago | from the easy-enough-kill-all-the-users dept.

Wireless Networking 251

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?"

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251 comments

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Just ask What would Jobs do? (4, Funny)

arcite (661011) | more than 3 years ago | (#37002428)

Then stand up and announce on the loud speaker in a polite English accent to everyone; "So you guys have a choice: Either turn off your Wi-Fi (devices) or I give up. Would you like to see the demos?" ......"Then all you bloggers need to turn off your notebooks. Go ahead, just shut the lids. I'll wait," he said.

I'm sure everyone will understand.

FYI Steve Jobs routinely uses out of spec channels (4, Interesting)

tlambert (566799) | more than 3 years ago | (#37002632)

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

Re:FYI Steve Jobs routinely uses out of spec chann (1)

Anonymous Coward | more than 3 years ago | (#37002738)

Channel 13 is allowed almost everywhere except the US. Channel 14 is the Japan-only one.

What is damned is alot of equipment is hard-wired to not allow channels over 11 worldwide, lest someone go use it in the US - lowest common denominator and all that.

Re:FYI Steve Jobs routinely uses out of spec chann (0, Offtopic)

Anonymous Coward | more than 3 years ago | (#37002826)

What is damned is alot of equipment

I did not realize that there was an Alot [blogspot.com] that was made of equipment.

Re:FYI Steve Jobs routinely uses out of spec chann (1)

nathana (2525) | more than 3 years ago | (#37002954)

How do you know that he did this, out of curiosity?

-- Nathan

Re:FYI Steve Jobs routinely uses out of spec chann (1)

Anonymous Coward | more than 3 years ago | (#37003452)

How do you know that he did this, out of curiosity?

-- Nathan

I am unsure if the channel 13 statement is true. I was in the room at WWDC when that happened, and I'd run up some tools on my laptop as the Wi-fi behaviour was awful.

There were over 1200 Mi-Fi type devices , a couple of hundred Android phones acting as wireless hotspots, and about 400 laptops sharing their interconnections.

I'd have thought the military term for nearly 2,000 Wi-fi networks in the same room was broad spectrum jamming ;)

Get ye some 802.11a. (4, Informative)

FooAtWFU (699187) | more than 3 years ago | (#37002430)

802.11a has a lot more spectrum. Aside from that, hoping that you can drown out everyone else's screaming really isn't going to work.

Alternatively, install a giant metal Faraday cage. (Good luck with that.)

Re:Get ye some 802.11a. (0)

Anonymous Coward | more than 3 years ago | (#37002460)

I vote Faraday.

Re:Get ye some 802.11a. (0)

Anonymous Coward | more than 3 years ago | (#37002484)

seconded. Copper mesh is damn sexy if you integrate it well

Re:Get ye some 802.11a. (0)

Anonymous Coward | more than 3 years ago | (#37002548)

TGIF ! (Thank God Its Faraday)

Re:Get ye some 802.11a. (1)

artor3 (1344997) | more than 3 years ago | (#37002778)

It's not that hard to make a bench top Faraday cage. Just make a wooden frame, and nail some copper mesh all over it. It won't be as good as the professional ones, but it doesn't need to be.

The problem is that people coming by your booth will now see a kludgy mess of wood and wire, instead of your nice, elegant demo.

Re:Get ye some 802.11a. (1)

SEWilco (27983) | more than 3 years ago | (#37003236)

It's not that hard to make a bench top Faraday cage. Just make a wooden frame, and nail some copper mesh all over it. It won't be as good as the professional ones, but it doesn't need to be.

The problem is that people coming by your booth will now see a kludgy mess of wood and wire, instead of your nice, elegant demo.

That is what they see if you build it that way. If you instead put your demo inside a glass or plastic box, with metallic tint coating on the inside and bright lighting inside, they'll see your demo under glass with the sides covered with mirrors. Whether they realize that they're also looking through a mirror is irrelevant.

Re:Get ye some 802.11a. (1)

Anonymous Coward | more than 3 years ago | (#37003260)

A Faraday cage to block or strongly reduce 2.4Ghz signals doesn't have to be that ugly, since the allowable size of holes in the mesh is dependent on the wavelength. 2.4Ghz is a wavelength of just under 5 inches. A 2-inch grid could easily be incorporated in to the right kind of industrial-themed decor.

Re:Get ye some 802.11a. (2, Funny)

Anonymous Coward | more than 3 years ago | (#37002876)

Alternatively, install a giant metal Faraday cage. (Good luck with that.)

I second this. We had one of those cheap plastic Faraday cages, and it did not work worth crap. Last time I try to pinch pennies with the Faraday cage I tell ya.

Re:Get ye some 802.11a. (3, Funny)

Culture20 (968837) | more than 3 years ago | (#37002982)

I second this. We had one of those cheap plastic Faraday cages, and it did not work worth crap. Last time I try to pinch pennies with the Faraday cage I tell ya.

Unless he bites, it's often easier to just put your Faraday on a leash.

Re:Get ye some 802.11a. (1)

Anonymous Coward | more than 3 years ago | (#37002890)

This!

My company absolutely has to use 5GHz 802.11a at trade shows. We have a robotic telepresence platform and simply cannot keep a call going through the crowded 2.4GHz 802.11g spectrum. With the 5GHz we can have a stable demo without interference from every Tom, Dick, and Harry's little D-Link all set to channels 1, 6, and 11.

Re:Get ye some 802.11a. (1)

AvitarX (172628) | more than 3 years ago | (#37003092)

This was what I first thought, but was too lazy to check if iDevices and Android tablets use it (though I imagine the Lenovo think willl when it's out).

Does the fact that N uses the whole spectrum help (I would imagine the fact that other people's N does hurts at least).

Re:Get ye some 802.11a. (2)

chiasmus1 (654565) | more than 3 years ago | (#37003110)

802.11a will get around the interference from other 802.11b/g devices as well as any microwave ovens that might be there, but the real problem might be all of the water interference in the room. Trade shows are full of people, who are full of water, who block your signal.

Re:Get ye some 802.11a. (2)

dgatwood (11270) | more than 3 years ago | (#37003208)

If the original poster is responsible for the convention center Wi-Fi, what he/she can do is crank down the transmit and receive gain and add more access points. If he/she is a vendor on the trade floor, that might not be enough; if the convention center doesn't set up such high density Wi-Fi for everybody, then every other vendor is going to leave their base station hardware set at the default setting, which, while appropriate for a house in the suburbs, or maybe an apartment complex, is WAY TOO LOUD in a crowded convention hall. The more devices you get in close proximity, the more interference issues you're going to see. Of course, all the other non-Wi-Fi devices aren't affected by such changes, so this only works if most of the interference is actually coming from other Wi-Fi sources.

Alternatively, as you suggested, move to the 5 GHz band. (I assume that's why you were recommending 802.11a, but it isn't limited to "a"; you can also run 802.11n up there with some hardware.)

Finally, you can use a high-gain external directional antenna to provide coverage for just your section of the floor at high enough gain to drown out everybody else (e.g. a 25 dBi yagi pointed down from the ceiling or something). Bear in mind that this is the Wi-Fi equivalent of a tactical nuke, so you should expect retaliation from other vendors the following year....

Alternatively, try renting one of these guys [xirrus.com] and see how you fare. That said, this is probably the Wi-Fi equivalent of a fuel-air bomb, so again, talk to the nearby vendors and try to convince them to share your connection rather than making a further mess of the spectrum.

Re:Get ye some 802.11a. (1)

dgatwood (11270) | more than 3 years ago | (#37003436)

Oh, and for your iPhone and GSM or CDMA iPad hardware, you might consider a picocell instead.

Re:Get ye some 802.11a. (0)

Anonymous Coward | more than 3 years ago | (#37003502)

802.11a has a lot more spectrum. Aside from that, hoping that you can drown out everyone else's screaming really isn't going to work.

I agree that 802.11a is the way to go if you don't need much bandwidth. I've used it to set up a VoIP network in a large long term care facility where at least half of the residents had their own wireless networks set up in their rooms. Wireless G is like a soupy mess in high density areas.

tried and true (1)

Anonymous Coward | more than 3 years ago | (#37002434)

Try an RS232c null modem cable.

New Frequency? (4, Insightful)

BadPirate (1572721) | more than 3 years ago | (#37002444)

If your devices are 802.11n compatible, you could put your router in n only mode... The 5.4ghz band may be less crowded.

Re:New Frequency? (0)

Anonymous Coward | more than 3 years ago | (#37003150)

"n" is not the same as "5 GHz" - the 802.11n spec is perfectly legitimate in the 2.4GHz band (as it is, of course, in the 5GHz band). It is true however that b/g are only defined in the 2.4GHz band. The OP's devices, even if they are labeled "b/g/n," may only operate in the 2.4GHz band.

Mod your equipment to use another frequency. (1)

very1silent (2194890) | more than 3 years ago | (#37002448)

If you want your equipment to work with the current standards, you need to mod it to use another radio frequency. In their current as-written form, the 802.11* standards just don't have a way for equipment negotiate graceful degradation in this situation, and that's what it would take.

Re:Mod your equipment to use another frequency. (0)

Anonymous Coward | more than 3 years ago | (#37002766)

How about putting some real money into R&D to solve the problems of your crappy products?

With the growing use of Wi-Fi, this will become a standard issue, not just for the occasional convention hall. Hell, if I'm not mistaking a lot of crowded cities already suffer from this.

Changing the band is not a solution, since most of the users barely know how to connect their wi-fi devices, let alone configure them. That's why plug&play is so damn popular, so you better come up with a good solution, or your performance will be reflected in your sales.

Just my two energy credits.

Use channel 13? (0)

Anonymous Coward | more than 3 years ago | (#37002450)

It's a Japanese channel.

Re:Use channel 13? (1)

X0563511 (793323) | more than 3 years ago | (#37003288)

Yea, and the FCC (and any other licensee who notices and/or cares) can come curb-stomp you for it.

Partial solution: go 5 GHz (2)

volsung (378) | more than 3 years ago | (#37002458)

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.

Re:Partial solution: go 5 GHz (2)

volsung (378) | more than 3 years ago | (#37002468)

BTW, keep in mind that 802.11n is not synonymous with 5 GHz support. Some devices list 802.11n, but still only work on 2.4 GHz.

Re:Partial solution: go 5 GHz (0)

Anonymous Coward | more than 3 years ago | (#37002704)

As someone who has been in the exact same boat as you, the only real option is 5ghz with devices that support it. It's practically impossible to operate in a convention hall in 2.4 GHz band. I haven't tried any really high power output access points, but the problem is that your devices are going to get drowned out anyway. If there is anyway to use bluetooth you may have some luck there....

Re:Partial solution: go 5 GHz (0)

Anonymous Coward | more than 3 years ago | (#37002832)

I get to do this job every year. It is pretty much impossible. 5ghz is the only realistic answer, you really can't get anything else to work. Even if you can control the environment to some extent by eliminating APs, every attendee is now running around with a 2.4ghz wifi enabled device that is just going to pollute the channel scanning for friendly APs.

Insofar as phones go, lots of newer, higher-end phones do play well on 5ghz. Unfortunately that does not include iPhones which tend to be key for these demos.

Re:Partial solution: go 5 GHz (0)

Anonymous Coward | more than 3 years ago | (#37003246)

While the 5GHz is probably ideal, not all the devices will support connecting to it. The other option would be BlueTooth. BlueTooth shares the 2.4GHz band with 802.11b/g, but it's designed to hop around to avoid interference, so it will likely be more reliable than 2.4GHz WiFi. This comes at the expense of bandwidth, but a 1mbps might be good enough for his use case. Again, it's not as clean a solution as the 5GHz band, but the phones you mentioned are more likely to be compatible.

Illegal (0)

Anonymous Coward | more than 3 years ago | (#37002470)

Illegally, you could pick up your wifi equipment from a country that allows channels higher than 11. I don't know what those frequencies are used for in the US, but there's a better chance you won't pick up interference (depending on what those frequencies are actually used for). Or, of course, use 5GHz (a or n). Less range, but also less interference.

Use the right tool for the right job (0)

Anonymous Coward | more than 3 years ago | (#37002488)

Get a good enterprise class AP + controller. The controller will do most of the job avoiding interference, auto channel utilization, etc. Saves your time and headache.

Channel 14 (0)

Anonymous Coward | more than 3 years ago | (#37002494)

It's technically illegal but if you set your router and network card location to japan (I think), you can use channel 14 which is quite far (on the spectrum that is) from the "standard" channels. Most wifi devices physically support this but they may be limited by the driver

5 GHz band (1)

Zarquon (1778) | more than 3 years ago | (#37002512)

At least for the laptops. There's a lot more spectrum there, and it's much less saturated. Probably not an option for the phones, though. Also, wired ethernet when possible.

Csma ca look it up (0)

Anonymous Coward | more than 3 years ago | (#37002538)

It's why wired networks are better

also interferes with sleeping (0)

Blymie (231220) | more than 3 years ago | (#37002544)

This is a big problem for me. Every time I travel, I get interference when I sleep.

Here's what happened last time:

http://www.youtube.com/watch?v=guGchg4mbLs [youtube.com]

not much you can do. (0)

Anonymous Coward | more than 3 years ago | (#37002546)

Use a omni-directional antenna that has as much gain as you can afford, and avoid channel 6.

Alternately, crank up a wifi monitor and show that there are 200 separate networks in 15 channels, and then run everything via cat 5/usb.

Use the right tool for the right job (1)

painkiller14 (2430616) | more than 3 years ago | (#37002554)

Get a enterprise class AP + controller. That will help you to do auto channeling, interference avoidance, etc. Saves lots of your time and effort.

Power ! (0)

Anonymous Coward | more than 3 years ago | (#37002556)

Use a dish off the access point pointed at the device under demonstration.
Overpower the interference. This would be especially true if it truly is background (lights and such) but
will work just fine overcoming 'The Masses"

Go lower. (0)

Anonymous Coward | more than 3 years ago | (#37002562)

Below channel 1 :).

A problem... (3, Informative)

fuzzyfuzzyfungus (1223518) | more than 3 years ago | (#37002570)

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...

Re:A problem... (1)

hedwards (940851) | more than 3 years ago | (#37002882)

Part of that has to do with all the products being fixated on longest distance possible. Which is understandable, but these days one doesn't necessarily want the signal to be that strong as interference with other people's equipment is a much more significant problem than getting a strong enough signal. Whenever I go to set up a new device around here I wind up finding at least a dozen different wireless networks all set up.

It's even worse at a convention like this where you're likely to have even more devices closer together.

Working together (0)

Anonymous Coward | more than 3 years ago | (#37002578)

You may be able to politely suggest to your neighbors that everyone turn down their signal and agree upon a pattern of channels that do not overlap, thereby

1) reducing the possiblity that your closest neighbors are directly interfering and
2) limiting the amount of signal that interferes with your next-closest neighbors.

As an example, think of the coloring structure of a political map, where two entities of the same color cannot touch.

-sweBs

Two choices (1)

sjames (1099) | more than 3 years ago | (#37002596)

Same two options as always. Either overpower [sharenator.com] the interference or turn off interfering devices with a universal remote [wikia.com]

Faraday cage! (2)

OzPeter (195038) | more than 3 years ago | (#37002614)

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.

More AP's (0)

Anonymous Coward | more than 3 years ago | (#37002622)

and directional antennas, if your literally 6 foot away from an AP with a +6 db ant pointing in your general direction your going to have a hell of a hard time not getting a connection, one in each corner of your exhibit area should do the trick.

Have an Android? (0)

Anonymous Coward | more than 3 years ago | (#37002630)

There are plenty of tools to try to find free channels:
https://market.android.com/details?id=com.farproc.wifi.analyzer&feature=search_result

Also make sure you've got security enabled, otherwise everyone and their brother will try to connect and probably overwhelm the router.

3.5 - 3.6 GHZ Wimax gear. (0)

Anonymous Coward | more than 3 years ago | (#37002634)

Look into WiMAX gear in the 3.5 to 3.6ghz range. You should be able to find a home router and usb or pcmcia gear for your laptops. Cell phones on the other hand are probably a no go.

Wrong assumptions (5, Informative)

mrmagos (783752) | more than 3 years ago | (#37002638)

Given this:

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.

Re:Wrong assumptions (0)

Anonymous Coward | more than 3 years ago | (#37003188)

Kudos for the correct use of the word "this". As opposed to the often seen

This.

that's prevalent on Slashdot nowadays.

Faraday cage (1)

TheTyrannyOfForcedRe (1186313) | more than 3 years ago | (#37002662)

best option is to use 802.11a (0)

Anonymous Coward | more than 3 years ago | (#37002674)

One solution is to use 5GHz network (802.11a) which has lot more channels than 2.4 GHz band (802.11b/g). But some of the devices you mentioned do not support 802.11a (eg. iPods). Although you could get mobile phones and pads that have dual band support (2.4 & 5). You could also try running your network at a higher power (look in your router configuration) and maybe use better antennas than those that come with the router by default. Also you could squeeze some more performance by running your network in 802.11g only mode, hence will not work for 802.11b devices.

Channel 14 (0)

Anonymous Coward | more than 3 years ago | (#37002678)

If your router supports it, switch it to channel 14. You can do this with most open source firmware (dd-wrt) - Beware, it is not legal - but I doubt the FCC is going to bust you for it. Channel 14 should have a lot less traffic, and might be usable.

Beamforming (2)

kaiser423 (828989) | more than 3 years ago | (#37002690)

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 [cisco.com]

802.11n (1)

portalcake625 (1488239) | more than 3 years ago | (#37002708)

Get a N class router with Linux firmware support (I recommend the RT-N16 + DD-WRT/Tomato). Set it up to run at 300Mbps on the dual-band and the transmit power upped to 100 or 125. It's practically a 2.4GHz G wireless jammer.

I know this problem well. (2, Insightful)

Anonymous Coward | more than 3 years ago | (#37002736)

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.

Re:I know this problem well. (1)

bugs2squash (1132591) | more than 3 years ago | (#37003026)

It's also an inherent problem with conference centers gouging for wifi access. If it were reasonably priced the exhibitors would not go rogue.

Ask the convention organizers to pool resources (0)

Anonymous Coward | more than 3 years ago | (#37002768)

If the problem were fluorescent lights or something, then it wouldn't work before the convention. I'm pretty confident from your description that the problem is that you're all trying to use the same radio spectrum at the same time and there's just too many of you competing instead of cooperating.

Wifi radios are just that; radios. if you have too many, they all interfere with one another. I suggest that this is a problem for all the other people at the convention, too. Therefore, the people who put on this convention should have already heard such complaints (unless people are too embarrassed to complain?) and they should be happy to deal with this as a problem of the commons (radio waves in air).

So what needs to happen is that every exhibitor who requires wifi needs to get together with every other such as organize shared resources so you can all actually share the airwaves, instead of unsuccessfully trying to compete with everyone.

Every 6 or 7 exhibitors who are adjacent should share one Wifi router. That'll probably fix the problem.

Pay them (0)

Anonymous Coward | more than 3 years ago | (#37002772)

Most trade shows use enterprise-grade WiFi gear to provide WiFi access on the floor and also to block unauthorised access points, i.e. your wireless router. They charge good money for their WiFi, but that is your best bet. You may also be able to negotiate with them to unblock your router.

RUN A CABLE (0)

Anonymous Coward | more than 3 years ago | (#37002774)

duh

Short answer: You Can't! (0)

Anonymous Coward | more than 3 years ago | (#37002788)

With the spectrum pollution in a trade show and the multitude of reflective surfaces getting any wireless connection to work reliably would require, as others have mentioned, either that everyone else shut down their equipment or that you and all of yours is enclosed in a fine mesh faraday cage. Even with all N capable equipment in the environment you describe, stable connections would be nearly impossible.

Spark Gap Generators are fun at conferences. (1)

HornWumpus (783565) | more than 3 years ago | (#37002794)

Demo shutting down all the demos.

Wait till the last second to setup, leave your gear in hardened, conductive cases...EMP...clear networking.

I believe you are boned. Go out of spec. Your going to have to go further then japan out of spec. Too many people will be on 13 and 14. Getting the phones working will be joy.

Get a 3g enabled phone for all the networks on the off chance that the telco overbuilt the conference floor. Leave a demo server available on the net just on the chance that your phones will have 'good enough' 3g connections. It would suck to be boned on 802.11* and only running on cables for the laptops (you know it's your backup plan), and find one of your personal smartphones still had connection, but no server configured.

Directional antenna (5, Insightful)

Scutter (18425) | more than 3 years ago | (#37002816)

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.

Get nearby booths or everybody on same network? (3, Insightful)

zootie (190797) | more than 3 years ago | (#37002836)

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.

Wifi won't work (1)

MichaelSmith (789609) | more than 3 years ago | (#37002958)

Wifi channel space has obviously been used up. Use either:

  1. 1. 3G cellular
  2. 2. Hard wired ethernet (no good for tablets, I know)

Re:Wifi won't work (1)

iMouse (963104) | more than 3 years ago | (#37003034)

Good luck using 3G cellular as during most of these trade shows, the cell towers are taxed as well. If you're lucky enough to get data, it won't likely be fast enough to leave a good impression on customers, nor would it be reliable.

Re:Wifi won't work (1)

MichaelSmith (789609) | more than 3 years ago | (#37003196)

Pull some cables then.

Couple of ideas (0)

Anonymous Coward | more than 3 years ago | (#37002968)

Use the 5Ghz range (either 802.11a or 820.11n) to get more channels.
You need reliability but if you don't need throughput reduce the channel width to as small as possible (usually whats supported by the station) to reduce interference.
Use directional antenna on the APs to reduce interference for the APs (won't help the omni stations though).
Use more APs running at lower power and more localised to the devices.
More mW is never better. Ask your neighboring stands to reduce the juice.

Dish Antenna (4, Insightful)

jmcharry (608079) | more than 3 years ago | (#37002980)

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.

If you want it to work for sure (0)

Anonymous Coward | more than 3 years ago | (#37002990)

use a cable!

Re:If you want it to work for sure (1)

maxwell demon (590494) | more than 3 years ago | (#37003548)

But WLAN cables are hard to get.

Try and Extricom (2)

freshdressed (1863944) | more than 3 years ago | (#37003020)

I used to set up networks for training and conferences my group did. We picked up an Extricom http://www.extricom.com/ [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

Intentional? (0)

Anonymous Coward | more than 3 years ago | (#37003042)

In my experience, the only way to get reliable service at a trade show is to pay fifty bucks a day to the company running the show. Not sure how they do it, but my cynical guess is that they deliberately pipe in interference.

some Food for Thought (0)

Anonymous Coward | more than 3 years ago | (#37003082)

On the first point I would recommend you stick with a simple ecosystem of same vendor / same model, or better then, with a spare one of another model of another vendor, just in case ;) (as far as monoculture is a concern, that would solve it). But the point is that routers of the same kind tend to have more reasons to interoperate better.

Another interesting choice : Make a map of the estimated coverage interlap of the routers in the field. Then colorize it with a color for each choosen channel, so that never two neighbors (closest overlapping person in that direction) share the same color.
With channel 1, 6 and 11, you would get 3 colors, but nstead of using 3 colors, use 4 colors by letting frequencies overlap better if 3 don't suffice. That would make channels 1, 5, 8, 11 (I prefer to give the extra space to the lowest frequency, on the logic that it spreads a bit better, so would be the least at ease).

Then, of course, if you could use some power control. Listen to neighbors, estimate their activity relatively to yours, and scale your power according to that difference. The less you're active, the less you merit to dispensate your imprint on the local spectrum.

My 2 cents, of course. But I admit I did a Ph.D in a related field.

some Food for Thought (1)

Vinz (99797) | more than 3 years ago | (#37003098)

[edit : sorry, that's the repost under my account. My bad.]

On the first point I would recommend you stick with a simple ecosystem of same vendor / same model, or better then, with a spare one of another model of another vendor, just in case ;) (as far as monoculture is a concern, that would solve it). But the point is that routers of the same kind tend to have more reasons to interoperate better.

Another interesting choice : Make a map of the estimated coverage interlap of the routers in the field. Then colorize it with a color for each choosen channel, so that never two neighbors (closest overlapping person in that direction) share the same color.
With channel 1, 6 and 11, you would get 3 colors, but nstead of using 3 colors, use 4 colors by letting frequencies overlap better if 3 don't suffice. That would make channels 1, 5, 8, 11 (I prefer to give the extra space to the lowest frequency, on the logic that it spreads a bit better, so would be the least at ease).

Then, of course, if you could use some power control. Listen to neighbors, estimate their activity relatively to yours, and scale your power according to that difference. The less you're active, the less you merit to dispensate your imprint on the local spectrum.

My 2 cents, of course. But I admit I did a Ph.D in a related field.

sudo aireplay-ng -0 1 (0)

Anonymous Coward | more than 3 years ago | (#37003136)

Startup aircrack. Deauthenticate all mac addresses but your own.

Try the other band (0)

Anonymous Coward | more than 3 years ago | (#37003138)

Bump up to 5GHz There's a lot less people with the good stuff.

This might work. (1)

Zaphod-AVA (471116) | more than 3 years ago | (#37003194)

Depends on the physical layout of what you are up to, but directional antennas on the mobile equipment and a 2.4ghz absorbing backdrop behind your stuff might work. Think old Pringles can style directional and a grounded copper mesh covered in cloth for the backdrop.

Blast through it with high gain antennas (1)

DrBuzzo (913503) | more than 3 years ago | (#37003226)

It's likely there's a lot of wifi and other traffic going around. You can probably overcome it with enough gain on the antennas. Directional antennas are best. You can send a beam out that is much higher power than the standard antennas that come with the router. You can go all the way up to dish-style antennas but that is probably going to be rather large and probably overkill.

If you can place routers and access points at multiple locations that would help too.

My advice would be this: Get multiple antennas and connect each to an independent router. Have them arranged in a circle to give full coverage - one facing north, one south, one east and one west etc, OR even do 8 in a circle. Make sure the beam width is good for this application. You can also add some dedicated (possibly even higher gain) antennas to cover areas of importance (like one pointed at a balcony area, one pointed toward the entrance area etc.

I'd recommend some good Yagi or directional panel antennas.

You can also put high gain external wifi antennas on the client side, like using high gain USB wifi adapters. That works okay for laptops, but for things like ipods, that is probably too cumbersome, so more focus on the infrastructure side.

Amplifiers can work too, but don't expect them to make the difference alone. Antennas matter more and amplifiers will boost your output signal but won't make as big a difference with the return signal. So I'd say use amplifiers but also lots of high gain antennas.

Oh, and this may, by the way, make it harder for others to get a good signal from their own wifi, but that's not your problem.

And a couple of important things to remember:
Trying to outpower everyone else's network may come down to being a pissing contest, but that doesn't mean you can't win.
Brute force works. If it doesn't work, that means you're not using enough of it.

Re:Blast through it with high gain antennas (0)

Anonymous Coward | more than 3 years ago | (#37003620)

Adding a higher gain antenna will only solve the downlink interference issue. The uplink towards the AP will still be a mess with 150 rogue APs floating around. This would be like trying to hear someone talking in a room full of people. Yes focusing where your listening helps but ultimately if there are still a ton of 'voices' in your path, you will still not be able to hear the intended person.

With an 802.11 AP you should also keep in mind that it uses a CSMA protocol which basically means everyone accessing the AP will transmit at random intervals. If by coincidence, two users transmit randomly but at the exact same time, the data will collide and be lost. The long and short of it is, as the number of users trying to connect to an AP increase, the quicker the overall system throughput decreases and the more terrible the performance becomes. Your only way around this is to either a) add more APs or b) change technologies (WiMAX/LTE). Of course, adding more APs will only add more interference thereby compounding your issues.

All that being said, my suggestion would be to go with a neutral-host cellular in-building solution, retransmitting an operator's LTE or WiMAX throughout the building and give up on unlicensed spectrum WiFi. The licensed frequency of this system and the higher 'legal' transmit power will increase the performance 10fold. Unfortunately, this will also increase the cost and you will give up control of the system but at least you could guarantee the system will work without a pissing contest!

You could ask the cellular operator to put WiFi on their DAS which will put the responsibility of the performance on them (getting rid of your headache).

One last thing, adding amplifiers and using higher gain antenna may put you over the power limitations of the 2.4GHz/5.8GHz band imposed by FCC. Depending on the ethical stance of your business, you may want to avoid going this route.

It might not be what you think (0)

Anonymous Coward | more than 3 years ago | (#37003228)

Most hotels and convention centers locked in long-term Internet access contracts long ago, before Wi-Fi became the norm, and before free access became popular. The site's Internet provider might be intentionally crowding the spectrum so conference organizers are forced to pay for access, and attendees are expected to go through the conference organizers for a password.

You're not the only broadcaster... (0)

Anonymous Coward | more than 3 years ago | (#37003232)

The problem is that before the conference, no one is setup (or set up at weird times). Also, potentially depending on your conference, the conference organizers are running their own Wifi. This means that before the conference, your access point works great, and once the show starts, your access point is being drowned out by everything else.

If you're at a conference with central Wifi, you're probably screwed, because their APs are licensed and VERY LOUD (like Interop). If your conference doesn't have central wifi then using something louder will be helpful, but also switching to 802.11a will clear you more spectrum (possibly even if there is conference-wide wifi). Your other option is wimax, but it's hard to get a license these days because Sprint and Clear are using it for 4G cellular.

dd-wrt (0)

Anonymous Coward | more than 3 years ago | (#37003240)

Use dd-wrt and crank up the signal strength...

Buy equipment from japan (0)

Anonymous Coward | more than 3 years ago | (#37003252)

I seem to remember that Japanese wifi devices had channels 12&13. I don't think they are FCC approved though

better than wireless (1)

tverbeek (457094) | more than 3 years ago | (#37003298)

This doesn't meet the specs of the question, due to the particular devices you wish to support, and the fact that many of them are deliberately incompatible with it.... but there is a technology that I've used successfully many times in the past to overcome the problems inherent and unavoidable in any electromagnetic wireless communication system. This technology dramatically reduces signal attenuation due to distance, it reduces interference from external devices that use the same frequencies, it allows for dramatically higher data rates, and as a bonus it even adds a level of security/privacy: requiring extremely close physical proximity to sniff the signals. These features come standard with the tech itself, or can be enhanced with a special "shielded" version. There are even varieties capable of actually powering the devices. This technology is, of course: Wire.

One of these days I'm going to patent it, clean up on license fees for a few months before the patent gets invalidated, and retire to Mackinac Island.

Hardwire everything like in the old days (0)

Anonymous Coward | more than 3 years ago | (#37003304)

Hardwire everything like in the old days

Get a ham license (1)

scottbomb (1290580) | more than 3 years ago | (#37003330)

And then read up on microwave amplifiers and horn antennas. You can then run a lot more power on the 2390 - 2450 MHz band. Your router becomes the exciter, feeding the amp, feeding a horn.

Rediculous solution (0)

Anonymous Coward | more than 3 years ago | (#37003412)

1. Use a mist machine to both knock out the competing electronics and attenuate the other APs. Add a light show to hide the sabotage.
2. Make a video overlay for the demonstration if it could fail live.
3. See if your devices that can do networking over bluetooth or USB.

Cantenna (0)

Anonymous Coward | more than 3 years ago | (#37003482)

make a cantenna

i work at a convention hall (3, Interesting)

matang (731781) | more than 3 years ago | (#37003568)

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.

Be the loudest (1)

juventasone (517959) | more than 3 years ago | (#37003606)

Yes, switching to 5 GHz should help, but not all your equipment may support it.

The other solution is to overpower them. Something like this [engeniustech.com] can be cranked up to 19dBm assuming you only need internet-level speeds. You'll screw everyone else, but it should work.

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