| 单词 | WLAN (Wireless Local Area Network) |
| 释义 | WLAN (Wireless Local Area Network) A LAN that employs radio frequency (RF) or perhaps infrared (IR) transmission rather than a wired technology such as coaxial cable, twisted pair, or optical fiber. A typical WLAN comprises fixed-location transceivers known as access points (APs) to which client workstations and peripherals connect via RF technology.The access points typically are hard wired to switches and routers that interconnect them and provide access to servers.The APs are fitted with radio transceivers and omnidirectional antennas.The client transceivers, or network adapters, may be in the form of PCMCIA cards, although major computer manufacturers now offer laptops with built-in transceivers.The APs are located at central points where there is good line of sight (LOS) to the workstations and link quality, therefore, is best. Most WLANs are standards-based versions from the IEEE 802.11 Working Group.At the Physical Layer, the RF specifications include both direct sequence spread spectrum (DSSS) and frequency-hopping spread spectrum (FHSS). At the Data Link Layer, the medium access control (MAC) protocol is carrier sense multiple access with collision avoidance (CSMA/CA). Most WLANs operate in the 2.4 GHz 74570c23.qxd 9/11/07 12:37 PM Page 543 |
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