The primary 20 MHz channel is used for signalling and backwards compatibility, the secondary is only used when sending data at full speed.Įxcept where noted, all information taken from Annex J of IEEE 802.11y-2008 These are generally referred to by the centres of the primary 20 MHz channel and the adjacent secondary 20 MHz channel (e.g. Īs shown in the diagram, bonding two 20 MHz channels to form a 40 MHz channel is permitted in the 2.4 GHz bands. However, using every fourth or fifth channel by leaving three or four channels clear between used channels can cause less interference than sharing channels, and narrower spacing still can be used at further distances. The overall effect is that if there is considerable overlap between adjacent channels transmitters they will often interfere with each other. However, the exact spacing required when the transmitters are not colocated depends on the protocol, the data rate selected, the distances and the electromagnetic environment where the equipment is used. North America Graphical representation of Wireless LAN channels in 2.4 GHz band. In 22 MHz channel width situations, there is 3 MHz free/unused spectrum between NON-overlapping channels, this is not called guard band but channel spacing. This guardband is mainly used to accommodate older routers with modem chipsets prone to full channel occupancy, as most modern Wi‑Fi modems are not prone to excessive channel occupancy. The remaining 2 MHz gap is used as a guard band to allow sufficient attenuation along the edge of the band. To guarantee no interference in any circumstances the Wi‑Fi protocol requires 16.25 to 22 MHz of channel separation (as shown below).
Most of the world will allow the first thirteen channels in the spectrum. Network operators should consult their local authorities as these regulations may be out of date as they are subject to change at any time. Nations apply their own RF emission regulations to the allowable channels, allowed users and maximum power levels within these frequency ranges. See also: Electromagnetic interference at 2.4 GHz § Wi-Fiįourteen channels are designated in the 2.4 GHz range, spaced 5 MHz apart from each other except for a 12 MHz space before channel 14. The following sub-bands are defined in the 802.11ah specifications: Thus, there is no global channels numbering plan, and the channels numbers are incompatible between world regions (and even between sub-bands of a same world region). Each world region supports different sub-bands, and the channels number depends on the starting frequency of the sub-band it belongs to. The ISM band ranges are also often used.Ĩ02.11ah operates in sub-gigahertz unlicensed bands.
Although channels are numbered at 5 MHz spacing, transmitters generally occupy at least 20 MHz, and standards allow for channels to be bonded together to form wider channels for higher throughput.Ĭountries apply their own regulations to the allowable channels, allowed users and maximum power levels within these frequency ranges.
In the standards, channels are numbered at 5 MHz spacing within a band (except in the 60 GHz band, where they are 2.16 GHz apart), and the number linearly relates to the centre frequency of the channel. Each range is divided into a multitude of channels. The 802.11 standard provides several distinct radio frequency bands for use in Wi-Fi communications: 900 MHz, 2.4 GHz, 3.6 GHz, 4.9 GHz, 5 GHz, 5.9 GHz, 6 GHz and 60 GHz. The radio frequency (RF) spectrum is vital for wireless communications infrastructure. Other equipment also accesses the same channels, such as Bluetooth. Wireless LAN (WLAN) channels are frequently accessed using IEEE 802.11 protocols, and equipment that does so is sold mostly under the trademark Wi-Fi. Aditing Short description|Wikipedia list article}}