Choosing from Among Available Wireless Protocols

The Institute of Electrical and Electronics Engineers (IEEE) started to look seriously at wireless networking in 1990. This is when the 802.11 Standard was first introduced by the Wireless Local Area Networks Standards Working Group. The group based the standard roughly around the architecture used in cellular phone networks. The wireless network is controlled by a base station, which can be just a transmitter attached to the network or, more commonly these days, a router.

Larger networks can use more than one base station. Networks with more than one base station are usually referred to as distribution systems. A distribution system can be used to increase coverage area and support roaming of wireless hosts. You can also employ external omnidirectional antennas to increase coverage area, or if required, use point-to-point, or directional antennas to connect distant computers or networks. Right now, the least expensive wireless Linux networks are built using devices (such as access points or NICs) supporting 802.11b, although the faster 802.11g devices tend to get more shelf space. Pretty soon we should start to see devices certified for the new 802.11n specification, offering larger ranges and significantly more power throughput, but this specification has yet to be formally agreed upon and is still some time off, despite the appearance of several pre-N enabled hardware.

An early standard, 802.11a, offers greater transmission rates than 802.11b, and a number of 802.11a wireless NICs are available (some products provide up to 72Mbps, but will not work with 802.11b devices). Wireless networking devices based on 802.11g, which has the speed improvement of 802.11a and is compatible with 802.11b, are becoming more widely available. Other wireless protocols include Bluetooth, which provides up to 720Kbps data transfers. Bluetooth is intended for short-range device communications (such as for a printer) and supports a typical range of only 10 meters. Bluetooth is unlike IrDA, which requires line-of-sight (devices that are aimed at each other). Bluetooth use conflicts with 802.11 networks because it also uses the 2.4GHz band. You can find out more by browsing to http://www.bluetooth.com/.

The 802.11 standard specifies that wireless devices use a frequency range of 24002483.5MHz. This is the standard used in North America and Europe. In Japan, however, wireless networks are limited to a frequency range of 2471MHz2479MHz because of Japanese regulations. Within these ranges, each network is given up to 79 nonoverlapping frequency channels to use. This reduces the chance of two closely located wireless networks using the same channel at the same time. It also allows for channel hopping, which can be used for security.

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