在目前的無線網路環境中，IEEE 802.11b通訊協定在MAC層的運作上，具有多速率(Multi-Rate)與單速率(Single-Rate)兩種不同的傳輸方式，使用戶端在距離基地台較近時選擇較高速率，較遠時則降低速率以確保封包傳輸不致遺失。而IEEE 802.11在防止封包碰撞機制方面，是使用CSMA/CA (Carrier Sense Multiple Access / Collision Avoidance)、RTS/CTS (Request To Send/Clear To Send)的機制來減低傳輸中封包產生碰撞的情況，但在啟用RTS/CTS機制後將導致傳輸節點的等待時間增長而降低傳輸流量。在本篇文章中，我們將分析影響無線網路傳輸的幾個因素，並比較這幾個因素在經由設定RTS門檻值來啟用RTS/CTS所呈現在效能上的差異；從上述的網路因素交叉分析實驗，我們得到最佳設定的RTS門檻值確實能有效的穩定傳輸效能。依此，我們接著模擬真實的無線網路環境，在單速率傳輸和多速率傳輸的模式下去分析RTS/CTS的最佳啟用時機。最後，我們歸納出在單速率環境停用RTS/CTS與多速率環境啟用RTS/CTS的結論，經過大量的模擬分析結果顯示，我們提出的論點確實可以明顯提高網路傳輸效能。

In the current wireless network environment, IEEE 802.11b communication protocol in MAC layer has two kinds of transmission methods under environment of Multi-rate and Single-rate. To ensure the unobstructed communication between stations and base stations that avoidance the packet loss in transmission. The mechanisms of CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance), RTS/CTS (Request To Send / Clear To Send) are used to reduce the opportunities of package collision during the transmission. However, the usage of RTS/CTS results in the long delay time and low transmission flow between stations. In this paper, we first analyze and compare several vital factors which influence the performance of RTS threshold under the wireless network transmission. Next, we demonstration RTS/CTS launch timing, which is obtained from the cross analysis under Single-rate and Multi-rate transmission. Finally, we propose a rule-based mechanism to improvement the transmission throughput at Single-rate transmission disabled RTS/CTS and Multi-rate transmission enabled RTS/CTS, through extensive experiments, the results that prove our scheme can improve the performance actually.

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