Wireless Network Setup and Channel Crossing

When you have a large area that will be covered by multiple AP's (access points) some strange things can happen. Interference is a big one. You can get interference ranging from microwaves all the way up to brick walls.

One thing to keep in mind is what type of wireless are you setting up. A\B\G\N (N is not yet released) are the flavors that are out there. I won't get into the specifics of the data bits or ranges, but it is good to know that B\G\N can work together or are cross compatible and backwards compliant. What is important are the channels they work on. For both B\G you get three clean channels from each those being 1,6 and 11.

Before installing the framework and have a working Internet connection it is a *great* idea to map out where you will install the AP's. I made the mistake of not mapping one time... never again. Start mapping out/site survey with your laptop and the free program Netstumbler. See if there are any other networks in the area what the SSID's are and what channel's they are operating on. Speaking of SSID's I recommend keeping them all the same for your network.

Depending on what type of wireless protocol you use, encryption level, outside interferences and other wireless networks in range you can map out the full network and install it in no time at all. Honestly the hardest thing about setting this up are the data runs from your framework.

Just for simplicity sake I will start with channel 1 on the first AP using 802.11g standard and no interference. Set your first AP 125ft - 150ft from your framework configured on channel 1. From that point map your next cell 125ft - 150ft away and use channel 6 then for the third AP use channel 11. Never crossing the same channels.

All of this changes when you have multiple flooring schemes and firewalls (the real brick and mortar kind) in the way. The point I'm making is that if you have all three AP's on say channel 6 they will cross each other and cause network connectivity issues/drop outs and disruptions. You should never have two AP's crossing each other on your network or others that are on the same channel.

After you have everything installed and working do another site survey and verify all of your AP's are on different channels, overlapping, the SSID's are the same, everything is encrypted and signal strength is strong. Store that data for future changes that may come about.

If you want a really good wireless networking tool that is far more advanced than Netstumbler I suggest Kismet and Cain and Able. I absolutely love both of those tools, but offered Netstumbler for ease of use and graphical depictions.

J