Ask Slashdot: Overcoming Convention Hall Wi-Fi Interference? 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?"
Just ask What would Jobs do? (Score:5, Funny)
I'm sure everyone will understand.
FYI Steve Jobs routinely uses out of spec channels (Score:5, Interesting)
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
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How do you know that he did this, out of curiosity?
-- Nathan
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Terry works at Apple.
Re:FYI Steve Jobs routinely uses out of spec chann (Score:4, Interesting)
"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).
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HE'S APPLE!
They use PROTOTYPE equipment all the time... He owns the peeps that can set the channel to whatever Steve wants.
It actually makes sense that Steve would set the network up that way.. It would also keep "nuisance" hackers out of his demo. It does make it extra funny to know Steve was using a channel people in the room should not have been able to access... Not a slightly geeky crowd much?
But on topic, short of having firmware access to unlicensed bands, there's not much you can do. Perhaps conven
Re:FYI Steve Jobs routinely uses out of spec chann (Score:4, Interesting)
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 [wikipedia.org]
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"...announce on the loud speaker in a polite English accent..."
FYI, this will not work. Steve Jobs does not have an English accent.
--Paul
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Steve Jobs does not have an English accent.
He does when he speaks French.
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Then we'll have to use Cary Elwes.
Get ye some 802.11a. (Score:5, Informative)
Alternatively, install a giant metal Faraday cage. (Good luck with that.)
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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.
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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.
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This. Or window screen. Or chicken wire. Or... (It doesn't have to be copper.)
Also, a Faraday cage doesn't have to be small. And the goal is not to create a totally isolated environment, but simply an en
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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. (Score:4, Funny)
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.
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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
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Oh, and for your iPhone and GSM or CDMA iPad hardware, you might consider a picocell instead.
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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.
Its not the vendors. At HIMSS a few years ago we had to go all spy vs. spy to share a single electrical outlet with our booth neighbor. This could have incurred a fine or ejection per the contract with the convention organizer/convention hall.
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Maybe.
If the receiving electronics in the mobile devices themselves are already being desensed from all of the local RFI, which may be the re
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Actually, it helps a lot. Remember that most traffic is downloading, so the base station statistically does a lot more transmitting than the clients. Even if transmit and receive were equal, though, cutting the shouting in half would still be a big improvement in total noise.
Also, you're forgetting that clients usually reduce their transmit power when possible to maximize battery life. By increasing the station density and lowering the power of the base station, you are significantly reducing the chances
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Jumping to the 5GHz spectrum would really be ideal because the problem almost certainly is 2.4GHz band congestion. Unfortunately most of your devices probably won't support the 5GHz band. The ipod touches and the wifi enabled cell phones certainly won't (unless all the cell phones are the Galaxy S2). 802.11n never should have been in the 2.4GHz band and should have been 5GHz only. I'm sure there is some idiot nearby you running a 2.4GHz AP in 802.11n mode, a setting which pretty much takes up the entire
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802.11a uses the (crowded) 2.4GHz range, as well as the (relatively unused) 5GHz range. Not a lot of consumer equipment supports 802.11a however (at least compared to 802.11g)
the 5GHz range is also used by 802.11n - which offers higher throughput than 802.11 a or g.
So much wifi equipment uses 2.4GHz that if you're getting too much interference here, if you switch to 802.11n and only broadcast your APs on 5GHz channels, you'll be amazed at how much better it is.
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I think you're reversing the two. 802.11a is strictly 5GHz, while 802.11n is either 2.4 GHz or 5GHz.
Most 802.11n hardware that has 5GHz support should also do 802.11a, but it's not a hard rule.
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Or have your display panels upholstered with this stuff:
http://www.lessemf.com/fabric.html [lessemf.com]
Get A Tinfoil Hat! (Score:2)
New Frequency? (Score:4, Insightful)
If your devices are 802.11n compatible, you could put your router in n only mode... The 5.4ghz band may be less crowded.
Partial solution: go 5 GHz (Score:3)
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.
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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.
5 GHz band (Score:2)
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.
A problem... (Score:4, Informative)
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...
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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 devi
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Right, but the standard doesn't really take into account the fact that most of these devices are being used in small spaces. My parents house is only like 25x25 and three stories tall. The furthest distance the signal ever needs to get is like 40 feet or so.
Individuals in condos or apartments likely need even less range than my folks do.
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Two choices (Score:2)
Same two options as always. Either overpower [sharenator.com] the interference or turn off interfering devices with a universal remote [wikia.com]
Faraday cage! (Score:3)
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In my experience trying to find nice 'free' wireless, I'd also note that I've had my best results with linksys
Wrong assumptions (Score:5, Informative)
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 (Score:4, Informative)
I'll go with Upgrade The Access Point...
Quoting a post to the SoCal FreeNet list on July 21, 2011 by Matt:
Just an interesting tidbit. I was asked to help out with the soccer game at Qualcomm Stadium last night. They had a special area on the field for the photographers and wanted to be able to have the photographers connected to the net to upload their pictures to their respective news agencies without leaving the field. Just off the tunnel that the players come out is the "media room" where we have just a little Netgear wireless router/access point for the photographers to use during Chargers games, so I just grabbed that, ran 280 ft of CAT-5 out to the field plunked down the Netgear, and set it to WPA2 encryption. I tested it thoroughly the day before the game. The next day, a few minutes after the game started, I got called down to the field because the wireless wasn't working. Everyone was associated with the SSID, but it wouldn't pass any traffic. So I power cycled it, and went back upstairs, and was called back down within minutes. With all the fans in attendance, many of them with wireless enabled smartphones, keeping track of all the wifi in the air must have been too much for the little Netgear, the thing couldn't pass traffic for more than 5 minutes between reboots.
So, plan B, went up to the media booths which weren't really being used for this game, and snagged a crusty old Cisco Aironet 1121B (yes, 802.11b) and put it in place of the Netgear on the field, even left it unsecured as I didn't have time to much about with it. Long story short, not a peep out of it the rest of the game.
I had been told many years ago, that what happens is the mac table of the cheaper wifi gear gets full trying to keep track of all the mac addresses it sees flying around the air, but I haven't confirmed this. Long story short, an old crusty Aironet is better than a fancy new consumer grade AP for large events any day of the year.
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Faraday cage (Score:2)
Re:Assault Rifle (Score:2)
http://en.wikipedia.org/wiki/Assault_rifle [wikipedia.org]
Re:Nicolas Cage (Score:5, Insightful)
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The fact that this was modded "Insightful" adds a sublime ridiculosity to the Slashdot Friday Night.
Beamforming (Score:2)
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]
I know this problem well. (Score:2, Insightful)
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
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Spark Gap Generators are fun at conferences. (Score:2)
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
Directional antenna (Score:5, Insightful)
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.
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Re:Directional antenna - even outdoors antenna (Score:2)
There's a lot of different directional antennas out there.
Get nearby booths or everybody on same network? (Score:3, Insightful)
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 (Score:2)
Wifi channel space has obviously been used up. Use either:
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Pull some cables then.
Dish Antenna (Score:5, Insightful)
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.
Try and Extricom (Score:2)
Toms Hardware Test (Score:2)
This might work. (Score:2)
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.
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Take this a step further and run an actual Pringles-can directional. Even if the cantenna doesn't work, the novelty factor of running one, or trying to, in order to overcome the white-noise like interference might draw extra foot traffic. "I see you're rolling bootleg. What else have you got?"
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better than wireless (Score:2)
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 f
i work at a convention hall (Score:3, Interesting)
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Please elaborate more on the actual devices that you use to achieve this. Brand names would help, links even better.
I'm not thinking of using this stuff as a trickster, It's for industrial/commercial use. The last job I did had two dozen WAPs (think big box stores.)
Thanks!
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There are plenty of security devices that support disabling unauthorized access points.
Aruba is the best at it. An ideal corporate configuration would be an entirely centrally managed Aruba network. It has this all built in.
However, you can google the concept of a WIPS and employ one of those.
http://en.wikipedia.org/wiki/Wireless_intrusion_prevention_system [wikipedia.org]
AirDefense, Aruba, etc, etc,
I've done consulting work on a dozen or more large retail implementations. I could have someone email you if you're intere
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Thanks! You gave me enough terms to google with.
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Every enterprise AP maker that I've seen supports this feature. It's essentially a tick box on the feature list, and has been for a long time.
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Be the loudest (Score:2)
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.
Avoid consumer-grade gear. (Score:2)
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
CSMA makes this a tough problem (Score:2)
CSMA (Carrier Sense Multiple Access) makes this a problem. The way this works is the AP and clients listen before transmitting. If they hear another signal above a certain threshold they will try to cooperate by not transmitting until the channel is clear. It's like trying to hold a conversation with a room full of people talking.
5 GHz will probably not work as your client equipment is most likely not equipped with 5GHz capable radios. If they have mini PCI cards you could upgrade them but otherwise your st
There is an invention called a directional antenna (Score:2)
Cooperation is both the Problem and the Solution. (Score:2)
Solved this before (Score:3)
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handheld 0~~~coax~~~~~|
handheld 1~~~coax~~~~Mixer~~~coax~~~~wifi router~~~ethernet~~~server
handheld n~~~coax~~~~~|
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Wait -you want to do WHAT with wifi?! Where!? (Score:2, Troll)
Wifi is inherently unregulated. It will have interference and lots of traffic from all the users and devices using the same ISM band. Everything from phones to toys to microwave ovens running in the green room of the booth next door which has a set dressing budget larger than your annual revenue.
You are all unlicensed users and get to accept whatever QoS or lack thereof that you get. There's nobody to whine to, or whine about. It is what it is. On the other hand, there are scary licensed users on that band
Dlink, Linkys, and Netgear (Score:2)
Is the problem. It works fine before the show starts and goes to shit after because the AP's are now keeping track of thousands of wandering WiFi enabled cell phones. Consumer grade AP's just can't handle it, some of them will even crash due to their MAC tables filling up (they still have to keep track of MAC addresses even before they authenticate)
In the future, invest $100 in a used Cisco Aironet off ebay. They cost $650 new while your Dlink costs $50 new for a reason.
Get your amateur radio licence... (Score:2)
... and configure your devices to work in the 13cm "high speed data" segment.
A few ideas... (Score:2)
I have run the networking at several 600-1200 attendee conferences, and have a few things you might want to try...
If any of your devices can use 5.2GHz, make sure you deploy APs for that. 5.2GHz has way more spectrum, and in my experience it tends to work where 2.4GHz is pretty spotty. Try deploying with fairly narrow beam antennas like 90 degrees, so you are just covering your booth, ideally mount it up high looking down. Run at the lowest power setting you can. Use 802.11n equipment, which often see
RF advice (Score:2)
Since your hardware isn't as flexible as it could be, you can't get away with tricks like special channels and using inbetween spectrum.
So with standard equipment and standard frequencies:
1) Use 802.11n, 5 GHz if possible (less crowded)
2) Try the wider modes (HT40) to see if they can hop around your interference better (just force it and see what happens)
3) Put metal bug screen around the back of your posters and such, (with your AP not behind them). This will decrease sensitivity to whatever is behind your
Oh this is an easy one (Score:2)
Reroute the phase coils through the plasma regenerator, then boost the particle stream with a subspace flux inducer. If that doesn't work, try routing your signal through an anti-neutrino pulse, you should be able to generate one by modifying the main deflector.
It's amazing what you can learn about this stuff from a combination of Star Trek reruns and a complete lack of practical experience!
My solution... (Score:2)
In the late 80s I worked for an exhibition company and we built a huge pond made up like Portsmouth Docks which ran a couple of remote controlled boats that punters could play with, and were meant to take part in a timed race. (Left unsupervised of course, they much preferred the sport of ramming each other until one sank). The first version used standard 27MHz rad
Stack implementation, MIMO and ch. 14 (Score:2)
I wrote code for the 802.11b stack, and have gotten a lot of feedback from the test team as well, and here is my 2c:
1. Stacks should handle at least 127 radios on one channel, but most implementations crash with as few as 8 radios alive. Make sure you use a stack that handles many radios. Test your router and your gear (netgear and D-link passed, but check with your current router anyway)
2. Nearby channels appear as noise. If you have many TX on nearby channels, you may not have enough signal/noise ratio. M
2.4 Ghz 5 Ghz (Score:2)
Set up the public network on 2.4 Ghz and your own network on 5Ghz. Done and done????
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Yea, and the FCC (and any other licensee who notices and/or cares) can come curb-stomp you for it.
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use a cable!
"The devices we use at the trade shows are... ...iPods/iPads, Android tablets, and a variety of Wi-Fi enabled cell phones."
Still looking for that RJ45 jack on my BlackBerry...
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There are plenty of tools to try to find free channels:
https://market.android.com/details?id=com.farproc.wifi.analyzer&feature=search_result [android.com]
While I personally use that program, at least on my EVO (Synergy GodMode ROM) once it starts seeing 20+ APs it tends to bog down so much it's about useless, even in simple "list" mode.
HEX
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I've the same app on my CM7's Color Nook. Works great, and I've not noticed an issue with lots of APs... although I've only seen up to 25 or so at once, no bogginess, etc.
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Yes, mod it. Because this is not only legal, but trivial to do as well... Oh, hang on a minute, no it's not.
What will be the easiest (and legal) way to do it is to use wireless n on the 5GHz band which will be far less crowded than 2.4GHz.
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RUN A CABLE
Great idea! Now where's the RJ45 jack on this here iPad again?
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Like -5 or something? You could try sqrt -2, I'd bet not many APs do that one.