1, 6, 11 or 1, 7, 13?

If you want even better separation between channels, using 1, 7, 13 would be better than 1, 6, 11.  The main reason everyone (including myself) references 1, 6, 11 is that almost all countries allow for these channels, some add 12 and 13 and Japan adds 14.  So, in reality, using a 1, 7, 13 "Three Channel System" in Europe and Australia would give even better separation, and using a 1, 7, 13, 14 "Four Channel System" in Japan would give the best coverage using 4 non-overlapping channels.

More Information On Overlapping Channel Issues

Now, if you are using devices with high quality transmitters and receivers, you'll notice interference from other devices on other channels that are not on your network even if those signals are well below -50 dBm.  This won't help your network throughput at all.

A Wi-Fi data packet that is sent across a Wi-Fi network is sent using a mechanism known as CSMA/CA which basically means that the following is done when sending data:

• Listen to see if there's anything being sent across this channel
• If the channel is inactive/idle, then send your traffic
• If the channel is active, wait until the transmission has ceased and then add a random additional period (known as the contention period)
• Rinse and repeat (from the initial listening step).

Those amongst us whose eyes have not glazed over from all of this technojargon (yes, I'm TRYING to keep it simple) will probably have just seen the issue that overlapping channels causes - the device is listening to the channel that it is operating on to see if there's traffic being transmitted and it is NOT listening to all of the other available channels.  That means that if you have correctly configured your network to run on, say, Channel 1 and a device on some other network that's incorrectly configured to use Channel 4 is spewing forth data, your transmitter will not recognise this data, resulting in it transmitting its legitimate data packet over the top of the Channel 4 rubbish, turning this transmitted packet of data into something between Jibberish and complete nonsense and requiring it to be retransmitted.

Had the technomoron who configured their Wi-Fi network chosen to use Channel 1, your device would hear the transmission, recognise it as valid data, wait, listen and then transmit during a quiet period.  Sure, the data would need to wait before being transmitted, but it wouldn't turn from valid data to slop between the transmitter and the receiver.

Now that, dear friends, is exactly why those people who use intermediate 802.11b/g channels need to be hunted down and shown this article - education is the aim of the game here, and teaching people how to use available resources sensibly is the way to go.