History Edit

Etymology and terminology Edit

Wi-Fi certification Edit

Versions Edit

There are many different versions of Wi-Fi: 802.11a, 802.11b, 802.11g, 802.11n (Wi-Fi 4[40]), 802.11h, 802.11i, 802.11-2007, 802.11-2012, 802.11ac (Wi-Fi 5[40]), 802.11ad, 802.11af, 802.11-2016, 802.11ah, 802.11ai, 802.11aj, 802.11aq, 802.11ax (Wi-Fi 6[40]), 802.11ay. Generation IEEE Standard Maximum Linkrate Wi‑Fi 6 802.11ax 600–9608 Mbit/s Wi‑Fi 5 802.11ac 433–6933 Mbit/s Wi‑Fi 4 802.11n 72–600 Mbit/s Equipment frequently support multiple versions of Wi-Fi. To communicate, devices must use a common Wi-Fi version. The versions differ between the radio wavebands they operate on, the radio bandwidth they occupy, the maximum data rates they can support and other details. In general, lower frequencies have better range but have less capacity. Some versions permit the use of multiple antennas, which permits greater speeds as well as reduced interference. Historically, equipment has listed the versions of Wi-Fi that it supports, but the Wi-Fi alliance has now standardised generational numbering so that equipment can indicate that it supports Wi-Fi 4 (if the equipment supports 802.11n), Wi-Fi 5 (802.11ac) and Wi-Fi 6 (802.11ax). The alliance have stated that the generational level 4, 5, or 6 can be indicated in the user interface when connected, along with the signal strength.[40]

Uses Edit

Wi-Fi radio spectrum Edit

Main article: list of WLAN channels The 802.11 standard provides several distinct radio frequencies ranges for use in Wi-FI communications: 900 MHz, 2.4 GHz, 3.6 GHz, 4.9 GHz, 5 GHz, 5.9 GHz, and 60 GHz bands.[56][57][58] Each range is divided into a multitude of channels. Countries apply their own regulations to the allowable channels, allowed users and maximum power levels within these frequency ranges. The ISM band ranges are also often used.[59] 802.11b/g/n can use the 2.4 GHz ISM band, operating in the United States under Part 15 Rules and Regulations. In this frequency band equipment may occasionally suffer interference from microwave ovens, cordless telephones, USB3.0 hubs, and Bluetooth devices. Spectrum assignments and operational limitations are not consistent worldwide: Australia and Europe allow for an additional two channels (12, 13) beyond the 11 permitted in the United States for the 2.4 GHz band, while Japan has three more (12–14). In the US and other countries, 802.11a and 802.11g devices may be operated without a license, as allowed in Part 15 of the FCC Rules and Regulations. A standard speed Wi-Fi signal occupies five channels in the 2.4 GHz band. Any two channel numbers that differ by five or more, such as 2 and 7, do not overlap. The oft-repeated adage that channels 1, 6, and 11 are the only non-overlapping channels is, therefore, not accurate. Channels 1, 6, and 11 are the only group of three non-overlapping channels in North America. However, channels that are four apart interfere a negligible amount, much less than reusing channels.[60] In Europe and Japan where channel 13 is available, using Channels 1, 5, 9, and 13 for 802.11g and 802.11n is recommended. 802.11a/h/j/n/ac/ax can use the 5 GHz U-NII band, which, for much of the world, offers at least 23 non-overlapping 20 MHz channels rather than the 2.4 GHz ISM frequency band, where the channels are only 5MHz wide. The 5GHz bands are more strongly absorbed by common building materials, and usually give shorter range. As the 802.11 specifications evolved to support higher throughput, the bandwidth requirements also increased to support them. 802.11n can use double the radio spectrum/bandwidth (40 MHz- 8 channels) compared to 802.11a or 802.11g (20 MHz). 802.11n can also be set to limit itself to 20 MHz bandwidth to prevent interference in dense communities.[61] In the 5 GHz band, 20, 40, 80 and 160 Mhz bandwidth signals are permitted with some restrictions, giving much faster connections.

Communication stack Edit

Performance Edit

Multiple access points Edit

Increasing the number of Wi-Fi access points for a network provides redundancy, better range, support for fast roaming and increased overall network-capacity by using more channels or by defining smaller cells. Except for the smallest implementations (such as home or small office networks), Wi-Fi implementations have moved toward "thin" access points, with more of the network intelligence housed in a centralized network appliance, relegating individual access points to the role of "dumb" transceivers. Outdoor applications may use mesh topologies. An Extended Service Set may be formed by deploying multiple access points that are configured with the same SSID and security settings. Wi-Fi client devices will typically connect to the access point that can provide the strongest signal within that service set.

Hardware Edit

Network security Edit

Health concerns Edit

Alternatives Edit

A number other "wireless" technologies provide alternatives to Wi-Fi in some cases: Bluetooth, short distance network

Bluetooth Low Energy, a low-power variant

Zigbee, low-power, low data rate, and close proximity

Cellular networks, as used by smartphones

WiMax, provide wireless internet connection from outside individual homes Some alternatives are "no new wires", re-using existing cable: G.hn over existing home wiring, such as phone and power lines There are also several wired technologies for computer networking which in some cases will be viable alternatives, in particular: Ethernet over twisted pair

See also Edit

References Edit