Our wi-fi at work is ridiculously slow, will adding more range extenders improve it?

Solution 1:

I'm going to put this as gently as I can: Wireless networks (802.11) suck.

The 2.4GHz band (802.11b, g, and some n devices) is a festering pit of radio noise.
Everything from baby monitors to microwave ovens pollute this section of the spectrum, and the wanton proliferation of wireless networks has it so congested that you're frankly lucky to get 1Mbit speeds out of it in some urban areas (in the building my company is in the 2.4GHz band is unusable - average throughput is less than 100Kb/sec).

The 5GHz band (802.11a, some n, and the new ac draft standard) is better in terms of interference, but you wind up taking a penalty in overall range (because 5GHz signals get eaten up more readily by the little things people like to have in their buildings, like walls).

In both cases you're using a shared medium (wireless frequency) -- this means everyone else's signal is effectively your noise: the more people using the wireless link the worse this gets as devices are fighting a limited slice of frequency spectrum and time.

Wireless "range extenders" just make the problem WORSE -- the extender is now chewing up radio spectrum to relay traffic back to the base station (adding more traffic and congestion to the airwaves).

For more detail than you probably ever wanted to know about wireless networking, check out the blog posts the Server Fault team did when they were fitting out their office wireless network:

• A Studied Approach at WiFi - Part 1
• A studied Approach at WiFi - Part 2

So what can/should you do?

Ideally you should run cables to the high traffic locations, and leave wireless for things that are truly mobile (laptops going to the conference room, cordless VoIP phones, a "guest network", and stuff like that).
Like Sirex suggested there are other ways to go about running cable that don't require a major remodel (but please check your local building codes before you start throwing wires through your ceiling).

The ideal solution may not be practical, so the next best thing is to build a wireless network with multiple access points that use a wired backhaul to get to your main network.
Apple documents how to do this with the Airport Extreme on their site, and you can find similar guidance from other manufacturers.

Some other things to bear in mind:

• One WAP can support about 15-25 users (depending on how heavily they use the network).
  If you load WAPs/coverage areas above this number your performance will suffer.
• Your WAPs should have minimal coverage area overlap if possible
  Remember the signal from one set of devices (WAP+Clients) is just "noise" to the other sets.

Cisco has some basic guidelines on setting up a wireless network which make for good reading.
They also have more advanced documentation, but my Google-Fu is failing me at the moment.

Solution 2:

Whilst i agree with voretaq7's general sentiment, many devices don't give you a choice about whether to run wireless, and there are a few things you can do on the wireless side:

Firstly, iperf/jperf is a toolkit to test your bandwidth and see which areas are suffering. Run the iperf listener on a system with a good quality Gigabit wired connection, and run jperf on a test laptop - preferably one that matches the most common model your staff use, since chipsets and antenna setups have a lot to do with how well things work. Do several runs of the client in each location to be sure you are getting a consistent result.

Next is to determine what interference is actually present. There are lots of expensive solutions for this, but one that has worked remarkably well for me is Wifi Analyzer, a free Android app that allows you to see wifi signals in various different ways. (Make sure you do it on a device that supports 5 GHz - my Samsung Galaxy S2 does, and most newer equipment should support it these days.) This won't let you see non-802.11 interference from things such as microwave ovens or Bluetooth, but it's a good start, and very low-cost. (A similar tool on Windows is Xirrus' Wifi Inspector.)

In my experience, most urban areas have huge clutter in the 2.4 GHz band where there are only 3 non-overlapping channels (1, 6, and 11), and almost nothing in the 5 GHz band where all the channels are non-overlapping (23 of them in .au - your region may have more or less).

Use the channel graph view in Wifi Analyzer; if you can see more than one signal above -75 dBm or so in the non-overlapping 2.4 GHz channels, or if there are devices in any other channels (e.g. my neighbours have a pocket wifi device that has chosen channel 3), then chances are that your devices are fighting interference. Do the check for both 2.4 GHz and 5 GHz, and put your AP in the channels which have the least competition.

Lastly, even in a congested band, you can improve things by using an AP that works around interference. To my knowledge, Ruckus ZoneFlex APs are the only ones which can do this on a per-client basis in real time. (I'm unaffiliated with Ruckus - just a relatively happy customer.) Get a couple of ZF7982 or similar dual-band units, do dedicated cabling runs to each one, configure different SSIDs for 5 GHz and 2.4 GHz, and get your clients to use the 5 GHz SSID by default so that they're using the less-congested spectrum.

These APs are not cheap, but they constantly amaze me at how well they work in a congested spectrum, and if they're improving your staff productivity, they'll pay for themselves in a matter of days. If your boss is "buy something now, ask questions later" type, you could probably do this as the first step and have an immediate win, then tune things more once it's in place.

Solution 3:

I would first take a look at different locations with InSSIDer or Wifi Analyzer/Android and check the channel levels at different places in the building/floors, check the that the wifi channels used are free and not too busy. Try and space the different Apple access points on different WIFI channels, manually. Also check that you do not use in between/overlapping channels as that will cause interference and bad Wifi performance.

Check that the wifi channels are placed like the article suggest. http://windowsitpro.com/mobile/wi-fi-best-practices

If that still does not help I would get professional access points from Ubiquity UniFi 2.4Ghz,5GHz or Aruba Networks. The advantage with Ubiquity is that the controller software is included run on a standard PC and does not require a huge investment in controller hardware, but you do get a tool to manage the access points.