Channel in WiFi Infrastructure

WiFi infrastructure has basically very limited channels. In a crowded traffic, not all channel can be simultaneously used in order to minimize interference in the infrastructure.

Channel	Frequency	Channel	Frequency
1	2412 MHz	8	2447 MHz
2	2417 MHz	9	2452 MHz
3	2422 MHz	10	2457 MHz
4	2427 MHz	11	2462 MHz
5	2432 MHz	12	2467 MHz
6	2437 MHz	13	2472 MHz
7	2442 MHz	14	2477 MHz

Note that not all channels can be used in all countries. For example, North American (US & Canada) can only use channel 1-11. European uses channel 1-13. Japan uses channel 14. It highly depends on the regulation in each country.

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For IEEE 802.11b based WiFi infrastructure uses Direct Sequence Spread Spectrum (DSSS), we are looking at about 22 MHz of bandwidth for each transmitted station.

It means for a station transmitted on channel one (1) or 2412 MHz center frequency. It will occupy 11 MHz below the center frequency as well as 11 MHz above the center frequency. It unfortunately means it will occupy two (2) channels up, two (2) channels down or five (5) channels in total. Consequently, to minimize interference in the channel, the community should clear two (2) channels up, and two (2) channels down.