目前IEEE 802.16組織已經開發出IEEE 802.16j多躍轉傳標準以提升IEEE 802.16e網路效能，但由於引進IEEE 802.16j標準將造成一些在原有IEEE 802.16e中不存在的效能下降，例如低頻寛使用率及頻繁換手等問題，因此IEEE 802.16j標準提出了RS分群機制(RS Grouping)。在此論文中，我們注重在RS分群中的系統傳輸量及換手次數等效能提升，基於使用者隨機移動的特性，我們設計了一個換手次數最少化的RS分群演算法(Handoff-Minimizing RS Grouping Algorithm)，其方法是使用低換手機率的群組形狀來進行分群，也就是使用群組中各RS之相交邊最多的群組形狀，只要指定群組大小，系統的整體換手次數將會減到最少。此外，我們提出流量優先(through-first, TF)及延遲優先(delay-first, DF)兩種集中式下傳排程策略(centralize downlink scheduling policies)，其目標分別是希望最大化系統傳輸量及最小化平均延遲，在TF排程策略下，系統中封包佇列大小越大的使用者將有越高的優先權進行資料傳送，而DF排程策略則安排封包佇列等候時間越大的使用者有越高的優先權。實驗結果顯在適當的分群結果下，透過結合我們所提出的RS分群演算及TF/DF集中式排程策略，系統的傳輸量、延遲時間及換手次數等效能指標將有顯著明顯的改善，而DF策略不僅能使一般延遲減到最小，而且能為不同負載量的用戶提供更公平的資源分配。

The IEEE 802.16j MR standard has been developed to provide performance enhancement to the existent IEEE 802.16e network. However, the issues such as frequent handoffs and low spectrum utilization which are not encountered in IEEE 802.16e may be incurred in IEEE 802.16j. The RS grouping is one optional mechanism in the IEEE 802.16j MR standard to overcome these problems. In the thesis, we are interested in investigating the RS grouping performance enhancement in terms of throughput and handoff frequency. Based on Random-Walk mobility model, this thesis designed a Handoff-Minimizing RS Grouping Algorithm by utilizing the grouping patterns resulting in lower handoff probability, that is the pattern with more inner-boundaries among the patterns with the same preferred group size. The simulation results show that the handoff frequency of the considered MR network can be minimized using our grouping algorithm when the preferred group size is given, and thus verify our theoretical analysis. In addition, we proposed two centralized scheduling policies, the throughput-first (TF) and the delay-first (DF) policies, which object to maximize the system throughput and minimize average delay, respectively. By integrating our RS grouping algorithm and centralized scheduling algorithm, the simulation results show that the throughput performance are gradually increased under both the TF and the DF policies while the considered group size increased, which is due to the lower packet loss from frequent handoffs problem. Moreover, we show that the DF policy not only can minimize the average delay, but also provide the fairness property among different loaded users.

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