Wifi Site Survey

One thing that is helpful when deploying wifi devices is to do a site survey and see what existing access points are present. This way, you can choose the new router to operate on a channel that doesn’t interfere. Applications such as this one (Android) allow you to see what existing access points are available, and is very useful to see what existing wifi signals are present.

Armed with that information, a decision needs to be made on which channels to choose. You’d think that simply using a channel that’s not present is a good idea, right? Well, it turns out it’s actually not so simple. The general rule to follow is this (in order of importance), and applies to 2.4Ghz (Wireless G). If on Wireless N, its generally less of an issue, and most of the selectable channels are non-overlapping.

1. You want to choose channels 1, 6 or 11. Don’t use any other channel.

2. Choose a channel that isn’t being used, if possible.

3. If there are existing access points on 1, 6 or 11, still use one of them, but pick one with the least number of existing devices and/or weaker signal, which means they’re further away.

4. Whatever you do, do not choose any other channel! If you see an existing device on a channel not in 1.) try and diplomatically get people in charge of the space to adjust their channels to be one of the above, or if not possible, choose a channel from 1.) as far away from it as possible. These other channels overlap with the primary channels, and can cause interference. When faced with a choice, its generally better to have two routers on the same channel than two channels very close to each other. The former case the router’s will be forced to take turns with each other at reduced bandwidth, while in the latter case they cause interference.

To change the channel, go into the router configuration and look for something that looks like this.

Some background reading:

Why you want to choose 1, 6, 11, which are “non-overlapping” channels.

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