| Summary: | 碩士 === 國立中央大學 === 通訊工程學系在職專班 === 103 === 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.
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