October 2012
Intermediate to advanced
160 pages
2h 49m
Chinese
Content preview from 802.11n技術手冊
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802.11n-2009 導論
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圖 1-2 802.11n 會議行程滑鼠墊
實體層（PHY）強化
802.11n 的原始速度基礎即是多重輸入與多重輸出（Multiple Input/Multiple Output，
MIMO）技術，可以讓單一無線電頻道支援多重資料串流。在 802.11n 以前，傳送
器（Transmitter）與接收器（Receiver）為單一輸入與單一輸出（Single Input/Single
Output，SISO）設備。相同的資料串流自傳送器的天線往所有方向飛去，可能會撞上
牆或其他障礙物，而最後抵達接收器。如果在傳送器天線與接收器天線間的兩條路徑
無法同步，所產生的訊號可能會由於路徑間干擾而相當衰弱。這種現象被稱為多重路徑
干擾（Multipath Interference），它是網路設計者的災難，只要稍微移動存取點（Access
Point）就可以大幅改善它的涵蓋範圍。當客戶端設備在周圍移動時，可能會因為多重路
4
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第一章
徑干擾使其「熱點（Hot Spots）」成為「冷點（Cold Spots）」。 在 MIMO 系統中，傳送
器與接收器可以利用多重路徑。每個路徑都採用不同組的資料，因此傳輸就不會受到多
重路徑干擾的破壞性影響。事實上，如果沒有多重路徑的因素 ...
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