在IEEE 802.16(d) 網狀網路下一個能增強服務品質支援的媒體存取控制層排程方法

Abstract

IEEE 802.16(d) 標準（俗稱WiMAX）是一個對於固定無線寬頻存取(FBWA)系統有著相當優異的技術，而在這個標準內定義了兩個模式。首先，一點對多點模式(PMP mode)可以幫助解決傳統在有線網路上「最後一哩」的問題。再來，網狀模式(Mesh mode)則被設計用來建構下一代的無線都會區網路。而在802.16網狀模式中，網路資源的分配可以用中央集權式(centralized)及分散式(distributed)兩種排程模式來做處理。

在分散式排程模式中，迷你時槽(minislot)的利用度對於獲得好的媒體存取控制層的排程效能是相當重要的一項議題。在本篇論文中，我們提出了一個新的媒體存取控制層的排程方法（稱為“薄片式方法“）以改善網路資源的利用度。另外，此方法還可以被利用來提供更好的soft-QoS支援。在此方法中，我們提出了multi-grant及multi-request兩種機制，而它們的效能也與原本方法的效能做比較。

我們的模擬結果顯示出此薄片式方法大幅度的提升媒體存取控制層的迷你時槽利用度。因此，它可以獲得較好的應用程式效能及減少封包的延遲時間。此外，此方法亦提供了較好的soft-QoS支援。

The IEEE 802.16(d) standard (also known as WiMAX) is a promising technology for future fixed broadband wireless access (FBWA) systems. There are two operation modes defined in this standard. First, the point-to-multipoint (PMP) mode aims to replace the traditional wired last-mile solutions. Second, the Mesh mode is designed for the next-generation wireless metropolitan area networks (Wireless-MANs). In the 802.16 Mesh mode, network resource allocation can be handled in the centralized and distributed scheduling modes. In the distributed scheduling mode, the minislot utilization is essential to achieving good performances of MAC-layer scheduling. In this thesis, we propose a novel MAC-layer scheduling scheme, named “the slicing-based scheme,” to improve network utilization. Besides, it can be used to provide better soft-QoS support. Both the multi-grant and multi-request mechanisms in this scheme are proposed and their performances are compared against those of the original scheme. Our simulation results show that the slicing-based scheme significantly increases the MAC-layer minislot utilization. Thus, it generates good application performances and decreases the packet delay. In addition, our proposed scheme can better provide soft-QoS support.