在巔峰時間使用網路，容易有大量頻寬的需求而發生負載超重的情形，導致需求頻繁的碰撞而重複發生丟棄的狀況。該如何解決碰撞問題的發生? 就是要頭端能清楚當下網路負載的情況，所以我們利用DOCSIS規範中的另外一個參數競爭窗口(Contention Window)來進行網路負載的預判，當頭端在成功接收需求後，可以區分大多數需求在哪個競爭區間，即可了解當下的網路狀況為何。在清楚網路情況後，就可以開始解決碰撞的問題，因此在本論文內提出兩種方法來進行改善，說明如下： Propose 1：將視網路情況來執行動態調整競爭窗口與DBS、DBE參數。 Propose 2：利用DOCSIS規範內原有的Null List機制的特性來暫緩部分用戶提出重傳或傳送需求。 綜上所述Propose 1與Propose 2是基本方法，其Propose 1的特點是當發生網路嚴重負載的情形，且有大量需求因無法傳送而被拋棄時，都能有效的解決；而Propose 2則適用在網路中度負載狀態，能在不調整參數的情況下去解決網路壅塞的問題。 我們再以這兩種方法為基礎又另外提出兩種整合方法，以平衡不同效能之表現，說明如下： 整合方法一(Propose 1 Modulated Propose 2)：整合Propose 1的有效解決碰撞需求與Propose 2不增加額外網路資源的特性。 整合方法二(Propose 2 With Dynamic Parameters)：在Propose 2的方法之中同步去調整競爭窗口與DBS、DBE參數。 結果得出對於較注重系統穩定性的業者可以使用第一種整合方法，以減輕網路壅塞的情形。而第二種整合方法可以提供給追求效率品質的業者使用，既可以保留網路寬頻的情況下，又擁有迅速解決碰撞需求的特性。;Under high traffic network conditions, a large of bandwidth requests may cause collisions to occur frequently. How do we solve this collision problem? That′s to determine the loading conditions of network, so we use one parameter of DOCSIS specification that is ”Contention Window” to determine the conditions of network. When CMTS gets the requests successfully, it could determine the loading of network by the timing of received requests in the contention window. When we understand the conditions, we could solve and improve the collision problem. In this paper, we propose two approaches as below： Propose 1：Determine the conditions of network to adjust DBS, DBE and Contention Window parameters. Propose 2：Use the feature of Null List mechanism in DOCSIS specification to pause the transmission request or retransmission request for users. Propose 1 and Propose 2 are the basic solutions. The propose 1 is able to reduce the collisions for bandwidth request on the heavy loading. The feature of propose 2 is used on the middle loading, it doesn′t adjust the parameters to improve the congestion of network. Based on above proposal, we provide the two integrated way. They have the different efficacy as follows： Propose 1 Modulated Propose 2：It combines the propose 1′s feature that reduce the collision for bandwidth request and the propose 2′s feature that doesn′t increase the overhead of network. Propose 2 With Dynamic Parameters：Adjust DBS, DBE and contention window parameters based on propose 2. The results show the combined 1 solution is suitable for the MSO that emphasizes stability system to reduce the congestion of network. The combined 2 solutions is suitable for the MSO that emphasizes efficiency system. It could keep the bandwidth of network and solve the collision conditions quickly.
