October 2012
Intermediate to advanced
160 pages
2h 49m
Chinese
Content preview from 802.11n技術手冊
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設計與建置一個 802.11n 網路
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無線區域網路的容量來自於廣闊乾淨的頻譜，802.11n 沒有定義一段新頻譜供使用，相
反的它與 5 GHz 頻段裡的 802.11a 以及在 2.4 GHz 頻段裡的 802.11b/g 共存。隨著無線
網路已經被大家接受（甚至愛用），在 2.4 GHz 頻段裡的限制和其三個頻道變得更加明
顯，除了基本網路外的所有網路，無線區域網路需要在 5 GHz 頻段裡的額外可用容量。
5 GHz 頻段提供了更多頻道，加上能夠建立更小的覆蓋能力，故頻道的重複利用能力
更好。
不同於之前的實體層，802.11n 是可以同時使用 2.4 GHz（802.11ng）、 5
GHz（802.11na）無線電頻段。想要使用高容量時，可以同時使用兩者。
建置一個網路所需要的 AP 數量，是由網路系統預期的性能來決定。挑選一個設備作為
最糟情況的性能目標。目標設備往往會是一個單串流設備，例如電話或是平板電腦。估
計在網路上的設備數量和整個網路所需的性能，以得到一個「容量」並計算目標 AP 數
量。接下來基於所需的訊號強度來估計一個 AP 的覆蓋範圍，以提供適當的覆蓋範圍。
許多單串流設備需要將網路設計成訊號強度約為 -67 dBm，使用規劃工具以得到一個
「覆蓋」目標需要的 AP 數量。顯然的，要選擇較大的兩個數量。在許多環境中，會同
時考慮覆蓋及容量來配置 AP，在高密度的區域會使用密集的 AP 部署，低使用者密度則
會使用較稀疏的覆蓋計畫。當你建立網路的容量計畫時，容許足夠的容量，方可讓網路 ...
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.