"Blocking" technology for busy wifi zones?

My partner and I have been working diligently at trying to speed up our Ubiquiti Unifi wireless network. It ran at good speeds 18 months ago and is now slow. We've been in contact with Ubiquiti and have been systematically implementing changes in an effort to improve wireless speeds (record average speed, implement configuration change, record average speed,....).

Our boss suggested that we implement "blocking technology" to "tamp out" nearby wireless networks. (There are many; the office is located in downtown Denver.) I suppose there could be technologies out there that detect EM signals in the 802.11 range (2.4 or 5.0 GHz) and generate signals that are 180 degrees out-of-phase with the detected signals, producing destructive interference, but I would think the list of possible complications and the possible downsides of such technologies would out-weigh the upside.

Let me know if I'm wrong.
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Dave BaldwinFixer of ProblemsCommented:
The first downside is that it is against federal law to intentionally block or interfere with radio signals like that.  See here: http://www.fcc.gov/document/warning-wi-fi-blocking-prohibited

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Dave BaldwinFixer of ProblemsCommented:
I have wifi but I don't normally use because here at my apartment, I have detected up to 56 different wifi networks simultaneously transmitting.  And of course, there are not that many channels available.
There are typically two ways to block signals.

Active blocking, which is what you're talking about, jams other signals making them not work and, from what I've heard (I'm not a lawyer) are typically illegal in the US.

Passive blocking, I believe (again, not a lawyer - check with one to be sure) is allowed. With passive blocking, you're creating, in effect, a zone in which no signals can get in or at, but you're not interfering specifically with other devices. It may be possible to buy wifi blocking wallpaper or paint and paint your area. That should keep your wifi signals in and other wifi signals out. I don't have a brand to recommend, but the quick Google search I did shows that it's not super cheap.

There may be a few other options though.

1. Do all of your devices support the 5Ghz network? Most 802.11 devices run at the 2.4 GHz network range where there are limited channels and you have lots of devices. If you can switch to a 5Ghz network, you may find it less crowded.

2. Is there a microwave or a 2.4 GHz cordless phone in the area of the wifi? That can kill performance. Make sure to keep those away from the wifi.
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jdanaAuthor Commented:
Great responses. Some feedback...

Generating an "active blocking" destructive signal is illegal. That's understandable.
Our Unifi network has detected 162 other APs in the last 6 months. While many of these are roaming hotspots, many are fixed APs in nearby businesses. (I recognize the names.)
Our clientele all use our guest network and expect decent speeds. What standard allows the "toggle over" to 5 GHz? 802.11g? 802.11n?
We have rooms in the office that return good wifi speeds and rooms with horrific speeds. I've rotated Unifi units and checked the speed of the Ethernet drops to which the APs are connected. The fast or slow speeds always follow the room and not the AP device, which is a strong indicator of interference from external wifi signals. I could look into passive blocking technology in those rooms.
I suppose I could try to "out-muscle" my neighbors. We've kept the Tx power settings low in effort to reduce internal interference. We could try the opposite.
There are no cordless phones in the office. Of course, I can't control the tenants above or below us.
Dave BaldwinFixer of ProblemsCommented:
What standard allows the "toggle over" to 5 GHz?
That's a hardware issue.  You have to have a unit that is capable of using 5 GHz.  Many older units only support 2.4 GHz.

To lower the level of internally generated interference, get as many people off wifi and back on the wired network as you can.
Have you considered a second AP? You can have the Unifi's set up so that you can roam from one to the other. If the rooms that are having trouble are in one area, an AP over there could help.
Craig BeckCommented:
As others have said, your radios must accept interference and not cause destructive interference to other systems.  The fact that other devices are transmitting on the same frequency as you is not classed as destructive though.

The best way is to introduce some kind of Faraday Cage effect surrounding your building.  That will block outside interference (or reduce it) and let you use your radios with no (or less) interference from foreign radios.

To answer some of your questions:

Our clientele all use our guest network and expect decent speeds. What standard allows the "toggle over" to 5 GHz? 802.11g? 802.11n?
Band-steering is the term.  It's implemented slightly differently between vendors.  Some APs/controllers can enforce it, while some clients can also prefer one band or the other based on what's available.

I suppose I could try to "out-muscle" my neighbors. We've kept the Tx power settings low in effort to reduce internal interference. We could try the opposite.
With low power your APs will struggle to differentiate clients from foreign APs/clients.  You'll get drowned with noise.  If you increase the power (think of it like raising your voice) you may well see better results as that may increase the SNR, however that's not guaranteed and it heavily depends on your deployment in terms of AP positioning too.

5GHz is where you need to try to get your clients to.  If you can get all of your clients using 5GHz, that's a positive step and will likely improve things massively.  Don't expect to achieve this in the next 3-5 years though!
jdanaAuthor Commented:
Dave, Craig, and quizwedge, Thanks for the excellent feedback. I've been in contact with Ubiquiti repeatedly over the last two months. They get high marks for helping us optimize the network for a "crowded" wifi environment. We're experimenting with some long range (high power) Unifi units and units that work in the 5GHz range.

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