I just started in the IT department of a small company (200 users) and it's clear that one of the main problems that is driving everyone crazy is the spotty nature of the wireless connectivity throughout the office, particularly in certain conference rooms. This is a huge problem because the connection often drops during important presentations to clients.
I was hired to help ease the load on the existing IT admin, who has done a great job, but is overloaded with many other tasks to deal with. So I would like to try to help out with this wireless issue. I am looking for advice on the best way to solve this problem–a realistic troubleshooting methodology that does not require me to spend any money. So far, I've experimented with Ekahau Heat Mapper, which is free and helps create a site survey. But I'm not exactly sure what I'm looking for or if there are other programs/tools/methods I should try as well. Any advice would be greatly appreciated.
[Some background: The wireless setup consists of an HP ProCurve Mobility MSM (710?) controller that controls 10 access points throughout the building. There are three virtual wireless networks configured on the controller: one seems to be a default that cannot be changed, one is for internal employees and authenticates via Active Directory, and the third is a guest network for visitors. When I use HeatMapper, these show up as three different SSIDs, with different MAC addresses, all on the same channel. At first I thought maybe this would cause interference, but this seems to be the way the controller works;apparently, it automatically configures the channels to avoid interference from the other APs on the network.]
Best Answer
If you are using 2.4Ghz WLAN protocols then Channels 1,2 & 3 are too close to be used in a cell type layout like this. You want to use Channels 1,6 & 11 - Cisco have a good explanation of the issues in this article on the 2.4Ghz channel overlap problem and cell coverage strategies.
The primary effect of having channel overlap is poor throughput but the secondary effect will be that the various WLAN auto connect\zero-config services on your client PC's will be much more likely to drop an active connection and attempt to connect to an alternate. This behavior has been significantly improved in recent OS's but anything older than Windows 7 or recent OSX is likely to require some work tuning the client NIC settings to work optimally in a large distributed office WLAN like this if the channels are not widely separated. One other common source of trouble that I've come across were incompatibilities between the access point firmware and the client WLAN NIC settings - things like power management (aka CAM, Continuously Aware Mode) caused issues between early Intel Centrino WLAN adaptors and Cisco infrastructure that caused similar issues to those you describe. That issue was resolved years ago but there have been others and it's worth checking that there are no known issues with your specific client WiFi adapters and your AP's.
Things are much better in terms of the number of channels and the separation between channels in the 5Ghz spectrum - if your infrastructure supports 5Ghz 802.11n\a and the clients support it then set 5Ghz 802.11n as the preferred option for clients (or 802.11a which is only 5Ghz).
One other thing that is worth remembering is that there is a lot of junk in the 2.4Ghz spectrum. Try to get a basic spectrum analyser in to check that there isn't some other ambient noise source leaking into your environment, that can cause the sort of symptoms you describe too.