Wireless networking overview
Wireless networking technologies range from global voice and data networks, which allow users to establish wireless connections across long distances, to infrared light and radio frequency technologies that are optimized for short-range wireless connections. Devices commonly used for wireless networking include portable computers, desktop computers, hand-held computers, personal digital assistants (PDAs), cellular phones, pen-based computers, and pagers. Wireless technologies serve many practical purposes. For example, mobile users can use their cellular phone to access e-mail. Travelers with portable computers can connect to the Internet through base stations installed in airports, railway stations, and other public locations. At home, users can connect devices on their desktop to synchronize data and transfer files.
To lower costs, ensure interoperability, and promote the widespread adoption of wireless technologies, organizations such as the Institute of Electrical and Electronics Engineers (IEEE), Internet Engineering Task Force (IETF), Wireless Ethernet Compatibility Alliance (WECA), and the International Telecommunication Union (ITU) are participating in several major standardization efforts. For example, IEEE working groups are defining how information is transferred from one device to another (whether radio waves or infrared light is used, for example) and how and when a transmission medium should be used for communications. In developing wireless networking standards, organizations such as the IEEE address power management, bandwidth, security, and issues that are unique to wireless networking.
Wireless network types
As with wired networks, wireless networks can be classified into different types based on the distances over which data can be transmitted.
Wireless wide area networks (WWANs)
WWAN technologies enable users to establish wireless connections over remote public or private networks. These connections can be maintained over large geographical areas, such as cities or countries, through the use of multiple antenna sites or satellite systems maintained by wireless service providers. Current WWAN technologies are known as second-generation (2G) systems. Key 2G systems include Global System for Mobile Communications (GSM), Cellular Digital Packet Data (CDPD), and Code Division Multiple Access (CDMA). Efforts are under way to transition from 2G networks, some of which have limited roaming capabilities and are incompatible with each other, to third-generation (3G) technologies that would follow a global standard and provide worldwide roaming capabilities. The ITU is actively promoting the development of a global standard for 3G.
Wireless metropolitan area networks (WMANs)
WMAN technologies enable users to establish wireless connections between multiple locations within a metropolitan area (for example, between multiple office buildings in a city or on a university campus), without the high cost of laying fiber or copper cabling and leasing lines. In addition, WMANs can serve as backups for wired networks, should the primary leased lines for wired networks become unavailable. WMANs use either radio waves or infrared light to transmit data. Broadband wireless access networks, which provide users with high-speed access to the Internet, are in increasing demand. Although different technologies, such as the multichannel multipoint distribution service (MMDS) and the local multipoint distribution services (LMDS), are being used, the IEEE 802.16 working group for broadband wireless access standards is still developing specifications to standardize development of these technologies.
Wireless local area networks (WLANs)
WLAN technologies enable users to establish wireless connections within a local area (for example, within a corporate or campus building, or in a public space, such as an airport). WLANs can be used in temporary offices or other spaces where the installation of extensive cabling would be prohibitive, or to supplement an existing LAN so that users can work at different locations within a building at different times. WLANs can operate in two different ways. In infrastructure WLANs, wireless stations (devices with radio network cards or external modems) connect to wireless access points that function as bridges between the stations and the existing network backbone. In peer-to-peer (ad hoc) WLANS, several users within a limited area, such as a conference room, can form a temporary network without using access points, if they do not require access to network resources.
In 1997, IEEE approved the 802.11 standard for WLANs, which specifies a data transfer rate of 1 to 2 megabits per second (Mbps). Under 802.11b, which is emerging as the new dominant standard, data is transferred at a maximum rate of 11 Mbps over a 2.4 gigahertz (GHz) frequency band. Another newer standard is 802.11a, which specifies data transfer at a maximum rate of 54 Mbps over a 5 GHz frequency band.
Wireless personal area networks (WPANs)
WPAN technologies enable users to establish ad hoc, wireless communications for devices (such as PDAs, cellular phones, or laptops) that are used within a personal operating space (POS). A POS is the space surrounding a person, up to a distance of 10 meters. Currently, the two key WPAN technologies are Bluetooth and infrared light. Bluetooth is a cable replacement technology that uses radio waves to transmit data to a distance of up to 30 feet. Bluetooth data can be transferred through walls, pockets, and briefcases. Technology development for Bluetooth is driven by the Bluetooth Special Interest Group (SIG), which published the Bluetooth version 1.0 specification in 1999. Alternatively, to connect devices at a very close range (1 meter or less), users can create infrared links.
To standardize the development of WPAN technologies, IEEE has established the 802.15 working group for WPANs. This working group is developing a WPAN standard, based on the Bluetooth version 1.0 specification. Key goals for this draft standard are low complexity, low power consumption, interoperability, and coexistence with 802.11 networks.