October 2012
Intermediate to advanced
160 pages
2h 49m
Chinese
Content preview from 802.11n技術手冊
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第三章
比較 1：802.11a/g 對決 1x1 11n
因為成本考量的原因，許多客戶端設備已經實作了 802.11n。一旦產業的技術基礎往前
發展，將會很難取得較舊的晶片。即使許多電池供電設備僅有很低的整體傳輸量需求，
製造商有時會傾向於繼續使用 802.11b，然而晶片廠商會持續的更新他們的產品線，並
且將客戶推往最新的技術領域。即使設備在使用 802.11n 晶片上花費了很大的心力去減
少電池的消耗，但 1x1 的設計還是可以最小化耗電的無線電鏈路元件數量。幾乎每一個
具備 Wi-Fi 的手機都是使用單串流 802.11n，平板電腦也是如此。
在單串流 802.11n 的情況下，鏈結速率僅有小部分的性能增益。802.11n 在頻道中有多
8％的資料副載波，因此它可以支援的鏈結速率高出 8％，如表 3-2 所示。即使鏈結速率
不如文獻那麼高，使用 802.11n 設備也是合理的，因為在存取點的天線陣列可以透過最
大比率合成（MRC）等技術提高性能。
表 3-2 802.11a/g 與 802.11n 的速度對決
調變 / 編碼 802.11a/g 速度 802.11n（1x1, 20 MHz, Long GI）速度
PSK, R=1/2 6 6.5
QPSK, R=1/2 12 13.0
QPSK, R=3/4 18 19.5
16-QAM, R=1/2 24 26.0
16-QAM, R=3/4 36 39.0
64-QAM, R=1/2 48 52.0
64-QAM, R=3/4
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