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1、802.11无线局域网(wlan)摘要在这个计算机高速发展的时代,伴随着网络的技术的不断发展与应用。传统的有线局域网虽然有着信号传输稳定,传输质量也比较高,信号受房间格局、障碍物、气候、电磁干扰影响小等方面的优势。但随着人们对移动办公的要求越来越高,传统的有线局域网要受到布线的限制,高效快捷、组网灵活的无线局域网应运而生。无线局域网是不使用任何导线或传输电缆连接的局域网,而使用无线电波作为数据传送的媒介,传送距离一般只有几十米。无线局域网的主干网路通常使用有线电缆,无线局域网用户通过一个或多个无线接取
2、器接入无线局域网。在有线世界里,以太网已经成为主流的LAN技术有线网络在某些场合要受到布线的限制:布线、改线工程量大;线路容易损坏;网中的各节点不可移动。特别是当要把相离较远的节点联结起来时,敷设专用通讯线路布线施工难度之大,费用、耗时之多,实是令人生畏。这些问题都对正在迅速扩大的联网需求形成了严重的瓶颈阻塞,限制了用户联网。与有线局域网相比较,无线局域网具有开发运营成本低、时间短,投资回报快,易扩展,受自然环境、地形及灾害影响小,组网灵活快捷等优点。可实现“任何人在任何时间,任何地点以任何方式与任何
3、人通信”,弥补了传统有线局域网的不足。关键词:局域网,无线局域网,IEEE802.11,射频技术,扩频技术,调制解调技术,信道差错控制技术,分集技术,天线技术IITitle802.11wirelessLAN(WLAN)keytechnologyandapplicationAbstractInthiseraofcomputerrapiddevelopment,alongwiththecontinuousdevelopmentofnetworktechnologyandapplication.Thetra
4、ditionalwiredLANsignaltransmissionstabilityandtransmissionqualityishigher,signalbytheroomlayout,obstacles,climate,andsmallelectromagneticinterferenceeffectadvantage.Butaspeopleareincreasinglydemandingformobileoffice,thetraditionalwiredLANtolimitedtothew
5、iring,efficientfast,flexiblenetworking,wirelesslocalareanetwork(LAN)arisesatthehistoricmoment.WirelessLANisnotusinganywiresortransmissioncableconnectedtoalocalareanetwork,usingradiowavesasadatatransmissionmedium,transmissiondistanceisgenerallyonlytensof
6、meters.WirelessLANbackbonenetworktypicallyusecable,wirelessLANusersaccessthewirelessLANthroughoneormorewirelessaccess.Inthewiredworld,EthernethasbecomethemainstreamLANtechnologywirednetworkwiringconstraintsinsomecasesbesubjectto:wiring,rebuildingproject
7、large;lineiseasytodamage;eachnodeinthenetworkcannotbemoved.Especiallywhenthenodelinksshouldphasefromfarthe,layingdedicatedcommunicationlinewiringconstructiondifficult,expensive,time-consuming,infact,asmuchasdaunting.Theseissuesarerapidlyexpandingnetwork
8、ingneedsseriousbottleneckblocking,limitingtheusernetworking.IIComparedwiththewiredLANandwirelessLANhasdevelopmentoperationcostislow,thetimeisshort,quickreturnofinvestment,easyextension,affectedbynaturalenvironment,terrainanddisas