2.4 GHz (802.11b/g/n)
There are 14 channels designated in the 2.4 GHz range spaced 5 MHz apart (with the exception of a 12 MHz spacing before Channel 14). As the protocol requires 25 MHz of channel separation, adjacent channels overlap and will interfere with each other. Consequently, using only channels 1, 6, 11 is recommended in the US to avoid interference. In much of the world, the four channels 1, 5, 9, 13 are recommended. There are exceptions to this however, for example in the UK, where British Telecom recommend use of three channels 1, 6, 11. Using the 3-channel system is recommended, since many existing access points are on channel 6 by factory default, causing the channel 6 to be likely to be in use anyway.
Potential Wireless LAN by IEEE 802.11 clauses 18 (802.11b), 19 (802.11g) and 20 (802.11n). IEEE 802.11 clauses 14 and 15 also specify potential uses of this range, but did not see widespread implementation.
Countries apply their own regulations to both the allowable channels, allowed users and maximum power levels within these frequency ranges. Consult your local authorities as these regulations may be out of date as they are subject to change at any time. Most of the world will allow the first thirteen channels in the spectrum.
| Channel | Frequency (MHz) |
North America |
Japan | Most of worldA |
|---|---|---|---|---|
| 1* | 2412 | Yes | Yes | YesD |
| 2 | 2417 | Yes | Yes | YesD |
| 3 | 2422 | Yes | Yes | YesD |
| 4 | 2427 | Yes | Yes | YesD |
| 5* | 2432 | Yes | Yes | Yes |
| 6 | 2437 | Yes | Yes | Yes |
| 7 | 2442 | Yes | Yes | Yes |
| 8 | 2447 | Yes | Yes | Yes |
| 9* | 2452 | Yes | Yes | Yes |
| 10 | 2457 | Yes | Yes | Yes |
| 11 | 2462 | Yes | Yes | Yes |
| 12 | 2467 | NoB | Yes | Yes |
| 13* | 2472 | NoB | Yes | Yes |
| 14 | 2484 | No | 11b onlyC | No |
| *With 802.11g and newer only the channels 1, 5, 9, and 13 shall be used in order to obey the non-overlapping 20 MHz OFDM channel scheme borrowed from 802.11a. But please do a site survey first, then if channel 6 is already heavily occupied, follow the 3-channel system. | ||||
^A Earlier, in Spain the only allowable channels were 10–11, and in France 10–13. These restrictions have been removed since, and these countries are currently following the common European policy (channels 1–13).
^B In the USA, 802.11 operation in the channels 12 and 13 is actually allowed under low powered conditions. The 2.4 GHz Part 15 band in the US allows spread-spectrum operation as long as the 50-dB bandwidth of the signal is within the range of 2,400–2,483.5 MHz which wholly encompasses both channels 12 and 13. A Federal Communications Commission (FCC) document clarifies that only channel 14 is forbidden and furthermore low-power transmitters with low-gain antennas may legally operate in channels 12 and 13. However, channels 12 and 13 are not normally used in order to avoid any potential interference in the adjacent restricted frequency band, 2,483.5–2,500 MHz, which is subject to strict emission limits set out in 47 CFR §15.205.
In Canada, 12 channels are available for use, 11 of which at full power and the other (channel 12) is transmit power limited. However, few devices have a method to enable a lower powered channel 12.
^C Channel 14 is valid only for DSSS and CCK modes (Clause 18 a.k.a. 802.11b) in Japan. OFDM (i.e., 802.11g) may not be used. (IEEE 802.11-2007 §19.4.2)
^D Outdoor use of channels 1–4 is not allowed in Israel, although indoor use is permitted.
Read more about this topic: List Of WLAN Channels