List of WLAN channels This list of WLAN channels is the set of legally
allowed wireless local area network channels using IEEE 802.11 protocols, mostly sold under
the trademark Wi-Fi. The 802.11 workgroup currently documents use
in four distinct frequency ranges: 2.4 GHz, 3.6 GHz, 4.9 GHz, 5 GHz, and 5.9 GHz bands.
Each range is divided into a multitude of channels. Countries apply their own regulations
to both the allowable channels, allowed users and maximum power levels within these frequency
ranges. In some countries, such as the United States, licensed Amateur Radio operators may
use some of the channels at much higher power for long distance wireless access.
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).
Note that for 802.11g/n it is not possible to guarantee OFDM (Orthogonal Frequency-Division
Multiplexing) operation thus affecting the number of possible non-overlapping channels
depending on radio operation. Interference Concerns
As the protocol requires 16.25 to 22 MHz of channel separation (as shown above), adjacent
channels overlap and will interfere with each other. Leaving 3 or 4 channels clear between
used channels is recommended to avoid interference. The exact spacing required depends on the
protocol and data rate selected as well as the electromagnetic environment where the
equipment is used. When two or more 802.11b transmitters are
operated in the same airspace, their signals must be attenuated by -50dBr and/or separated
by 22 MHz to prevent interference. This is due to fact that the DSSS algorithm transmits
data logarithmically along a 20 MHz bandwidth. The remaining 2 MHz gap is used as a guard
band to allow sufficient attenuation along the edge channels.
Note: The 40 MHz bands in the diagram above are labelled with their centre channel numbers,
the management interface of many Wi-Fi devices labels these bands with the centre channel
of one of the 20 MHz bands they overlap plus an Up or Down notation to specify the other
half of the band i.e.: Channel 3 = Channel 1+Upper, or Channel5+Lower and Channel 11
= Channel 9+Upper or Channel 13+Lower. Countries apply their own regulations to both
the allowable channels, allowed users and maximum power levels within these frequency
ranges. Network operators should consult their 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be out of date as they are subject to change at any time.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. ^B In the USA, 802.11 operation in the channels
12 and 13 are 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.
3.6 GHz (802.11y) Except where noted, all information taken
from Annex J of IEEE 802.11y-2008 This range is documented as only being allowed
as a licensed band in the United States. Please see IEEE 802.11y for details.
Countries apply their own regulations to both the allowable channels, allowed users and
maximum power levels within these frequency ranges.
A 40 MHz band is available from 3655–3695 MHz. It may be divided into 8 5 MHz channels,
4 10 MHz channels,or 2 20 MHz channels, as follows:
4.9 GHz (802.11y) Public Safety WLAN 50 MHz of spectrum from 4940 MHz to 4990 MHz
(WLAN channels 20–26) are in use by public safety entities in the United States. Within
this spectrum space, there are two non-overlapping channels allocated, both with a width of 20 MHz.
The most commonly used channels are 22 and 26.
5 GHz (802.11a/h/j/n/ac) Countries apply their own regulations to both
the allowable channels, allowed users and maximum power levels within these frequency
ranges. Network operators should consult their local authorities as these regulations may
be out of date as they are subject to change at any time.
European standard EN 301 893 covers 5.15-5.725 GHz operation, and v1.7.1 is in force.
In 2007 the FCC (United States) began requiring that devices operating on 5.250–5.350 GHz
and 5.470–5.725 GHz must employ dynamic frequency selection (DFS) and transmit power
control (TPC) capabilities. This is to avoid interference with weather-radar and military
applications. In 2010, the FCC further clarified the use of channels in the 5.470–5.725 GHz
band to avoid interference with Terminal Doppler Weather Radar (TDWR) systems. This statement
eliminated the use of channels 120, 124, and 128. Channels 116 and 132 may be used, so
long as they are separated by more than 30 MHz (center-to-center) from a TDWR located within
35 km of the device. There are now at least five relevant KDBs about operation in 5 GHz
radar bands. Germany requires dynamic frequency selection
(DFS) and transmit power control (TPC) capabilities on 5.250–5.350 GHz and 5.470–5.725 GHz
as well, in addition the frequency range 5.150–5.350 GHz is only allowed for indoor use, leaving only
5.470-5.725 GHz for outdoor and indoor use. Since this is the German implementation of
EU-Rule 2005/513/EC, similar regulations must be expected throughout the European Union.
Austria adopted Decision 2005/513/EC directly into national law. The same restrictions as
in Germany apply, only 5.470-5.5725 GHz is allowed to be used outdoor and indoor.
South Africa simply copied the European regulations. Japan no longer allows 34, 38, 42, and 46
channels for connecting J52 supported old APs. Authorization to use these channels expired
in May 2012. In Brazil, the TPC use in 5.150–5.725 GHz
band is optional. DFS is required only in 5.470–5.725 GHz band.
Australian DFS channels also require TPC, or the maximum allowed power is cut in half.
As per AS/NZS 4268 B1 and B2, transmitters designed to operate in any part of 5250–5350 MHz
and 5470–5725 MHz bands shall implement DFS in accordance with sections 4.7 and 5.3.8
and Annex D of ETSI EN 301 893 or alternatively in accordance with FCC paragraph 15.407(h)(2).
Also as per AS/NZS 4268 B3 and B4, transmitters designed to operate in any part of 5250–5350 MHz
and 5470–5725 MHz bands shall implement TPC in accordance with sections 4.4 and 5.3.4
of ETSI EN 301 893 or alternatively in accordance with FCC paragraph 15.407(h)(1).
New Zealand regulation differs from Australian; see http://www.rsm.govt.nz/cms/licensees/types-of-licence/general-user-licences/short-range-devices
for details. In Japan, authorization to use channels 34,
38, 42 and 46 expired in May 2012, seven years after channels 36, 40, 44 and 48 were initially
allowed. ARIB STD T-71v5_2 clause 5.3.8.3.3 lists permitted channels.
China MIIT expanded allowed channels as of Dec 31 2012 to add UNII-1, 5150 ~ 5250 MHz,
UNII-2, 5250 ~ 5350 MHz (DFS/TPC), similar to European standards EN 301.893 V1.7.1.
5.9 GHz (802.11p) The 802.11p amendment, also known as Wireless
Access in Vehicular Environments (WAVE), published on July 15, 2010, specifies WLAN in the licensed
Intelligent Transportation Systems (ITS) band of 5.9 GHz (5.850-5.925 GHz). The 802.11p
standard is intended for use in vehicular communication systems.