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Today, WiFi is a very popular wireless networking technology. There are more than several hundreds of millions of WiFi devices. The development of this technology started in the late 1980s with the `WaveLAN <http://en.wikipedia.org/wiki/WaveLAN>`_ proprietary wireless network. WaveLAN operated at 2 Mbps and used different frequency bands in different regions of the world. In the early 1990s, the IEEE_ created the `802.11 working group <http://www.ieee802.org/11/>`_ to standardize a family of wireless network technologies. This working group was very prolific and produced several wireless networking standards that use different frequency ranges and different physical layers. The table below provides a summary of the main 802.11 standards.
Standard
Frequency
Typical throughput
Max bandwidth
Range (m) indoor/outdoor
802.11
2.4 GHz
0.9 Mbps
2 Mbps
20/100
802.11a
5 GHz
23 Mbps
54 Mbps
35/120
802.11b
4.3 Mbps
11 Mbps
38/140
802.11g
19 Mbps
802.11n
2.4/5 GHz
74 Mbps
150 Mbps
70/250
When developing its family of standards, the `IEEE 802.11 working group <http://www.ieee802.org/11/>`_ took a similar approach as the `IEEE 802.3 working group <http://www.ieee802.org/3/>`_ that developed various types of physical layers for Ethernet networks. 802.11 networks use the CSMA/CA Medium Access Control technique described earlier and they all assume the same architecture and use the same frame format.
The architecture of WiFi networks is slightly different from the Local Area Networks that we have discussed until now. There are, in practice, two main types of WiFi networks : `independent` or `adhoc` networks and `infrastructure` networks [#fBSS]_. An `independent` or `adhoc` network is composed of a set of devices that communicate with each other. These devices play the same role and the `adhoc` network is usually not connected to the global Internet. `Adhoc` networks are used when for example a few laptops need to exchange information or to connect a computer with a WiFi printer.
An 802.11 independent or adhoc network
Most WiFi networks are `infrastructure` networks. An `infrastructure` network contains one or more `access points` that are attached to a fixed Local Area Network (usually an Ethernet network) that is connected to other networks such as the Internet. The figure below shows such a network with two access points and four WiFi devices. Each WiFi device is associated to one access point and uses this access point as a relay to exchange frames with the devices that are associated to another access point or reachable through the LAN.
Component Translation Difference to current string
This translation Propagated Read only cnp3-ebook/protocols/wifi
The following string has the same context and source.
Propagated Read only cnp3-ebook/protocols/lan

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Glossary

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read-only
Source string location
../../protocols/wifi.rst:23
String age
3 years ago
Source string age
3 years ago
Translation file
locale/pot/protocols/wifi.pot, string 20