Wifi – Troubleshoot dropped wireless connections

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I was recently hired in the IT department of a small company (~180 users) and one of the issues that people have been complaining about is having their wi-fi connections drop during meetings. The company is using an HP ProCurve Wireless LAN with 10 APs and a controller unit located in the server room. I don't have any experience troubleshooting WLAN in a multi-AP environment, so I'm trying to at least gather information using free or cheap tools.

I did a basic site survey using the free version of Ekahau HeatMapper and discovered the following in one of the conference rooms that has been a problem. The program picked up three access points (plus a bunch of others with much lower signals that were out of range):

AP 1: SSID: "Unknown SSID" – Signal strength: -48 dBm – -40 dBm. Channel: 2

AP 2: SSID "CompanyMain" – Signal strength: -35 dBm or greater. Channel: 2. Security: WEP
(This is the main SSID for the company's WLAN.)

AP 3: SSID: "CompanyGuest" – Signal strength: -40 dBm – -35 dBm. Channel: 2. Security: WPA2
(This SSID is the company's "guest" WLAN, which was setup to allow Internet access, but prevent network access.)

Is there anything that you see that is clearly a problem from the above? I'm assuming that the unknown SSID might be a big problem, and that it is an AP from a neighboring office that is causing interference. Does that seem likely?

Also, regarding channel, should we try changing the channels of our APs to avoid interference with that unknown SSID? (Since everything seems to be on Channel 2?)

Should our APs be on different channels? In other words, should the CompanyMain and CompanyGuest APs be on different channels?

Finally, any recommendations for free/cheap tools to help me figure this out, and/or a good methodology to follow?

Thanks in advance for any help.
Jack

Best Answer

Those access points on channel 2 are probably interfering with both channel 1 and channel 6. Not bad work. You could try and move your access points to channel 11 and see if you get less interference, or have a word with your neighbours and tell them to use a more sensible channel for their access points. alt text http://jpoa.info/blog/wp-content/uploads/2008/09/80211-frequency-channel-map.jpg

you may even be able to move your access points to channel 14 (in some countries).

You need to avoid overlap. There are other sources of interference too, such as microwave oven's, street lighting, fluorescent strip lighting in offices.

you ap's should be on different channels, depending on their spacing.

Again, it maybe just the make and model of your client cards, not all wireless cards are created equally.

best to check your ap logs and see why disconnections are taking place.

http://wifi-doc.com/Cisco.Press-802.11.Wireless.Ne/1587051648/ch03lev1sec3.html

has some nice information and channel placement.

http://www.wifiyacht.net/wifi-adjacent-myth.html

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