IEEE Std 802.11a-1999無線區域網路通訊協定之效能評估與改善

Performance Evaluation and Improvement of the IEEE Std 802.11a-1999 Wireless LAN Protocol

黃學冠(Xue-Guan Huang)

指導教授 ： 劉玉蓀

中原大學/工學院/電機工程研究所/碩士(2001年)

https://doi.org/10.6840/cycu200100068

摘要

本論文對IEEE Std 802.11a-1999無線網路通訊協定的實體層與介面存取控制層做效能評估並提出改善方法。IEEE Std 802.11a-1999實體層利用正交分頻多工系統(Orthogonal Frequency Division Multiplexing, OFDM)來對抗多重路徑衰減的干擾，並以摺積碼搭配交錯器來更正由雜訊所造成的資料錯誤。本論文利用室內無線通道模型來模擬實體層的效能，經由模擬可得：以OFDM配合軟式摺積碼可以有效地降低封包錯誤率，封包錯誤率可以達到10-2~10-5之間。IEEE Std 802.11a-1999介面存取控制層是以載波偵測多重存取/碰撞避免(Carrier Sense Multiple Access with Collision Avoidance, CSMA/CA)分散式協調功能為最基本的協定。當通訊台個數大於通道個數時，隨著通訊台的增加，CSMA/CA的效能會快速的下降。本論文提出兩個利用模糊邏輯控制來改善CSMA/CA效能的方法。經由模擬證實，本論文提出的兩個方法能有效的降低封包錯誤率，進而提升系統有效流量。本論文同時也將探討CSMA/CA及兩個控制方法對通訊台大幅改變及無線通道環境的敏感度。

關鍵字：IEEE Std 802.11a-1999，正交分頻多工系統，載波偵測多重存取/碰撞避免，模糊邏輯控制。

關鍵字

IEEE Std 802.11a-1999 ； 正交分頻多工系統 ； 載波偵測多重存取/碰撞避免 ； 模糊邏輯控制

並列摘要

The IEEE Std 802.11a-1999 wireless LAN protocol is considered. The physical layer of IEEE Std 802.11a-1999 in which Orthogonal Frequency Division Multiplexing (OFDM) and convolutional code are used to combat frequency-selective multipath fading is simulated. The simulation results verify that OFDM and soft-decision convolutional code can reduce frame error rate to 10-2~10-5. The MAC layer of IEEE Std 802.11a-1999 adopts Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) as a basic medium access control technique. In this paper, two fuzzy logic control CSMA/CA protocol are developed. The simulation results show that both fuzzy logic control protocol successfully improve the performance of CSMA/CA. Finally, the sensitivity of CSMA/CA and the proposed protocol to the variation of the number of stations and channel noise is discussed.

Keywords: IEEE Std 802.11a-1999, OFDM, CSMA/CA, fuzzy logic control.

並列關鍵字

IEEE Std 802.11a-1999 ； OFDM ； CSMA/CA ； fuzzy logic control.

參考文獻

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