在WiMAX網路上，SS在傳送資料前必須先向BS傳送頻寬需求，待分配到頻寬之後才可以上傳資料。傳送頻寬需求的方式又分單點輪詢(Unicast polling)、群播輪詢(Multicast polling)與廣播輪詢(Broadcast polling)，本篇論文主要探討的是群播輪詢，並將非即時性服務之QoS（nrtPS、BE）分成數個群播輪詢群組。當SS數量增加的時候，相對傳送頻寬需求的次數也增加，若兩個SS同時在同一個競爭時槽中送出頻寬需求就會發生碰撞，使得BS無法接收到頻寬需求，換言之，BS無法得知SS在傳送頻寬需求當中發生了碰撞。本篇論文修改群播輪詢群組中SS傳送頻寬需求的MAC BR header來記錄碰撞訊息，根據不同的碰撞情形給予不同程度的量化加權，並藉此加權結果來計算該群組適當的競爭時槽長度。此外還提出一種有條件限制的競爭時槽比例計算方式，以提升優先權較高之群組成功傳送頻寬需求的次數。
論文的內容首先介紹WiMAX網路的標準—802.16規格，然後說明群播輪詢群組競爭機制，接著討論其他過去的競爭時槽分配方式，最後提出一個本篇的群播輪詢群組競爭時槽比例計算方式，並比較給予不同權重的QoS，其傳送頻寬需求的平均值，以及不同優先權的群播輪詢群組間競爭時槽比例的分配情況。

In WiMAX network, SS has to send bandwidth request to BS before transmitting data. After SS gets the allocated bandwidth from BS, SS is allowed to upload data. There are three methods to send bandwidth request, including unicast polling, multicast polling, and broadcast polling. In this paper, we focus on the multicast polling issue and divide different quality of services(nrtPS、BE) into several multicast polling group. When the numbers of SSs are increasing, the more collisions occur while at least two SSs send bandwidth request at the same time so that BS cannot receive bandwidth request. Therefore, BS is unable to know that whether SS has encountered collision during transmitting bandwidth request. Based on the reasons motioned before, this paper gives different weight to collision state for qualifying the degree of collision. The collision state is recorded by the SS''s MAC BR header when SS sends bandwidth request to BS. Therefore, BS can calculate the length of contention window for the group. In addition, we also proposed a method that has joins a beta to count the length of contention window, The method promotes high priority group to send bandwidth request effectively.
The paper provides a brief overview of WiMAX network standard at the beginning and presents the multicast polling group contention mechanism. Then the paper proposes a method to calculate the ratio of contention window of a multicast polling group, and compares the average value of bandwidth request and the allocation of contention window with different weight between different QoS and different priority for different group.

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