於移動WiMAX網路提出延伸即時性輪詢服務演算法改進上行資源分配之研究

Abstract

雖然在IEEE 802.16e標準規範中，針對不同物理特徵的訊務流定義五種不同服務品質要求(Quality of Service, QoS)的資源分配演算法，但是標準規範中並沒有明確提出具體解決方案保證維持服務品質，而這些種種問題近年來就成為許多實驗室研究的重點。在本研究中，我們針對使用延伸即時性輪詢服務演算法，運用在點對多點的無線網路模式上的移動終端裝置，提出了一種改進的上行鏈路資源分配演算法。該演算法可用來解決在不可預測的多變無線通訊環境裡，移動終端裝置因服VBR(Variable bit rate, VBR)訊務流的資料量會是週期性可變動的特徵，所造成移動終端裝置請求資源與獲得可傳輸資源的不匹配所面臨的問題。該演算法依據各個移動裝置請求表頭統計次數的變化，使基地台作到主動分配合理的上行資源給需求持續增加的移動裝置；改善原始延伸即時性輪詢服務演算法的缺點，降低資料封包遺失率及滿足延遲的要求。在模擬的結果顯示，此演算法的確可以有效地降低移動裝置在上行鏈路傳輸資料延遲時間及達到減少封包遺失率，維持服務品質的要求。

Although in IEEE 802.16e standard has five different resource allocations of QoS, the standard has not propose a suggestion of specific assurance to maintain QoS; however, these problems has been emphasized by studies in recent years. In this paper, an ertPS algorithm is used in the mobile terminal system of wireless network model to PMP. The goal of our algorithm, improving uplink resource allocation, is to solve the problem that the data rate of serving VBR traffic to be periodic and variable under unpredicted wireless communication condition. Due to the VBR traffic’s features, the mobile terminal device may face problems of the asymmetry of requested and available resources. According to changes of statistical frequency of request header at each mobile system, this algorithm ensures that the base station assigns uplink resources actively to the mobile devices whose requirement of resources have increased-; it also improves the shortcomings of the algorithm originally used in formal ertPS, which helps this research to decrease the packet loss rate and to satisfy the demanded delay of traffic. The simulation shows this research can reduce the transmission data delay during uplink and decrease the packet drop rate to guarantee the demanded QoS.