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Wireless Local Area Network (WLAN) is a network that enables devices to connect to the network wirelessly. WLAN uses radiated energy, commonly called high-frequency radio waves, to communicate amongst nodes.
Organizations that Influence WLAN Standards
The four major organizations that set or influence WLAN standards are described below:
ITU-R: International Telecommunications Union-Radio communication (ITU-R) is a worldwide organization of United Nations. It works for standardization of communications that use radiated energy. Its prime objective is to manage the assignment of frequencies.
IEEE: Institute of Electrical and Electronic Engineers (IEEE) is a society of technical professionals. It promotes the development and application of electro-technology and allied sciences. IEEE develops communications and network standards, among other activities. The organization publishes a number of journals, have many local chapters, and societies in specialized areas.
Wi-Fi Alliance: Wi-Fi Alliance is an industry consortium that encourages interoperability of products that use WLAN standards. The consortium runs a certification program and recognizes products, which are implementing WLAN standards, as Wi-Fi certified products.
FCC: Federal Communications Commission (FCC) is an independent US government agency. It regulates interstate and international communications by radio, television, wire, satellite and cable in the United States of America.
Modes of Wireless LANs
There are two modes of WLANs; ad hoc mode and infrastructure mode.
Ad hoc mode WLAN: An ad hoc network consists of two or more wireless devices that communicate directly with each other. The wireless local area network (WLAN) network interface adapters in the wireless devices generate omni directional signals within a limited range called Basic Service Area (BSA). When two wireless devices come within the range of each other, they immediately form a two-node network and are able to communicate with each other.
An ad hoc network is non-transitive.
Infrastructure mode WLAN: An infrastructure network consists of an access point that connects wireless devices to the standard cable network. An access point is connected to cabled network through a cable and it generates omni directional signals. When wireless devices come within the range of the access point, they are able to communicate with the cabled local area network.
The access point works as a central bridge device to include wireless devices in the cabled LAN.
Wireless Technologies
802.11: This is the latest networking specification for wireless local area networks (WLANs), developed by the Institute of Electrical and Electronic Engineers. It contains several sub-specifications , and the IEEE is constantly adding new specifications. This specification uses Carrier Sense Multiple Access with Collision Avoidance (CSMS/CA) media access control mechanism. 802.11 supports 1 or 2 Mbps transmission in the 2.4 GHz ISM band using Frequency Hopping Spread Spectrum (FHSS).
802.11x: It contains various specifications for the 802.11 family of Wireless LAN network standards. Some of the specifications in this family are still under development. The 802.11b specification uses Direct Sequence Spread Spectrum (DSSS) and supports 11 Mbps transmission in the 2.4 GHz band.
Infrared: Infrared technology uses invisible infrared radiations to transmit signals to short distances. There are two types of networks communication possible, one in which the sender and the receiver are visible to each other and are situated in a straight line known as line-of-sight mode; the other type of communication known as diffuse mode does not require the sender and receiver to be directly visible to each other. This technology is used in TV sets, cordless microphones, laptops, remote modems, printers, and other peripheral devices. Infrared networks use frequencies in the terahertz range and support transmission speeds of 1 to 2 Mbps.
Bluetooth: Bluetooth technology uses short-range radio frequencies to transmit voice and data signals at the speed of 1 Mbps on a frequency of 2.4 Ghz. Bluetooth is used to automatically synchronize information among different types of computers like desktops, laptops, and palmtops, or connecting to the Internet through a cell phone.
Important Protocols
WAP: Wireless Application Protocol (WAP) supports mobile computing. It was developed by the WAP forum. The functionality of WAP is equivalent to that of TCP/IP. WAP uses a smaller version of HTML called Wireless Markup Language (WML) to display Internet sites.
WEP: Wired Equivalent Privacy (WEP) is a security protocol for wireless local area networks (WLANs). It has two components, authentication and encryption. It provides security, which is equivalent to wired networks, for wireless networks. WEP encrypts data on a wireless network by using a fixed secret key. WEP incorporates a checksum in each frame to provide protection against the attacks that attempt to reveal the key stream.
