無(wu)(wu)線(xian)(xian)上(shang)網(wang)卡(ka)是一種(zhong)把UIM或SIM卡(ka)，集(ji)成到一個(ge)(ge)類似于傳統貓(mao)的(de)硬件設備，也就是說我們通(tong)過(guo)無(wu)(wu)線(xian)(xian)上(shang)網(wang)卡(ka)和以前通(tong)過(guo)電話線(xian)(xian)和貓(mao)上(shang)網(wang)是一樣的(de)，都需要撥號，只不過(guo)過(guo)去的(de)貓(mao)被現(xian)在的(de)無(wu)(wu)線(xian)(xian)上(shang)網(wang)卡(ka)取代(dai)，過(guo)去的(de)電話線(xian)(xian)被手機UIM和SIM卡(ka)替(ti)代(dai)，當(dang)我們想上(shang)網(wang)的(de)時候(hou)就讓終端設備通(tong)過(guo)這個(ge)(ge)無(wu)(wu)線(xian)(xian)上(shang)網(wang)卡(ka)連接internet即可。

無線(xian)(xian)上網(wang)卡(ka)的(de)(de)工(gong)作原(yuan)理是微(wei)波射頻(pin)技術(shu)，一般采用CDMA2000實(shi)(shi)現(xian)(xian)(xian)通(tong)訊，也可采用GPRS通(tong)訊。它遵循802.11g標準，通(tong)過無線(xian)(xian)傳輸，由無線(xian)(xian)接(jie)入點發出信號(hao)(hao)，用無線(xian)(xian)上網(wang)卡(ka)接(jie)受和(he)發送(song)數據(ju)(ju)。按(an)照IEEE802.11協議，無線(xian)(xian)上網(wang)卡(ka)卡(ka)分為(wei)媒體訪問(wen)控制(zhi)（MAC）層和(he)物(wu)理層（PHY Layer）。物(wu)理層能(neng)夠實(shi)(shi)現(xian)(xian)(xian)無線(xian)(xian)電(dian)信號(hao)(hao)的(de)(de)接(jie)收與發射，它與無線(xian)(xian)上網(wang)卡(ka)硬(ying)件中的(de)(de)擴頻(pin)通(tong)信機(ji)相(xiang)對應。物(wu)理層提供空閑信道估計CCA信息給MAC層，以便決定是否(fou)可以發送(song)信號(hao)(hao)，通(tong)過MAC層的(de)(de)控制(zhi)來實(shi)(shi)現(xian)(xian)(xian)無線(xian)(xian)網(wang)絡(luo)的(de)(de)CCSMA/CA協議，而MAC-PHY子層主要實(shi)(shi)現(xian)(xian)(xian)數據(ju)(ju)的(de)(de)打包與拆包，把必要的(de)(de)控制(zhi)信息放(fang)在數據(ju)(ju)包的(de)(de)前面，從而實(shi)(shi)現(xian)(xian)(xian)上網(wang)。