A. For best performance, you should choose a channel at least 5 channels from your neighbors' networks.

Although 802.11b and 802.11g devices are designed to share the airwaves with neighboring networks, it is best to find a clear channel for several reasons, chief among these:

1. When your neighbors' networks are busy, there is less available bandwidth on those frequencies for your data, reducing your performance

2. Your Access Point (AP) and wireless devices may not hear your neighbor's weaker wireless signals, causing degraded performance due to collisions

3. Your neighbor's networks may not be entirely 802.11b or 802.11g compliant. Some "advanced" technologies are known to interfere with 802.11-compliant systems instead of sharing the airwaves with them.

In order to find a completely clear channel, you need to choose a channel that is 5 or more channel numbers away from your neighbors. This is not always possible, particularly in heavily populated areas. So do your best. Tools such as Vistumbler or inSSIDer can help you visualize the WiFi landscape.

You need to understand that the wireless channels translate to a radio frequency. Channel 6, for example, is 2.437 GHz (or 2437 MHz). Each channel up or down is 5 MHz away. However, and this is key, Wi-Fi signals are 20 MHz wide! So when you set your Wi-Fi device to channel 6, you actually are using the frequencies of channels 5, 6, 7, and half of 4 and 8.

                     -10 MHz   2437 MHz  +10 MHz
---------01---02---03---04---05---06---07---08---09---10---11---------
                         ~~~~~CHANNEL 06~~~~~

So consider the situation below when 3 wireless networks are on 3 different, but adjacent channels, 5, 6, and 7. They may be different channels, but they are using much of the same spectrum and, as a result, they will contend with each other.

---------01---02---03---04---05---06---07---08---09---10---11---------
                    ~~~~~CHANNEL 05~~~~~
                         ~~~~~CHANNEL 06~~~~~
                              ~~~~~CHANNEL 07~~~~~

This is why it is recommended to try to be at least 5 channels (25 MHz) away from your neighboring networks. By doing so, you avoid overlapping the frequency spectrum that their networks use. By moving the network 5 channels away (6 minus 5 equals 1, or 6 plus 5 equals 11), you avoid any overlap. As follows:

---------01---02---03---04---05---06---07---08---09---10---11---------
~~~~~CHANNEL 01~~~~~
                         ~~~~~CHANNEL 06~~~~~
                                                  ~~~~~CHANNEL 11~~~~~

Notes: The channels available are governed by local regulations. You may have different channels available to you.

ed: Some tests have shown that the minor overlapping of channels does not degrade performance of Wi-Fi systems, allowing for four nearby networks to share the available spectrum. This article discusses both three and 4-channel placement:
»articles.techrepublic.com.com/51···866.html

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by funchords edited by No_Strings
last modified: 2010-10-31 20:58:14