PRCA: Priority and Reservation based OVSF Code Assignment in W-CDMA 陳彥亦、黃培壝
E-mail: [email protected]
ABSTRACT
W-CDMA (Wideband Code Division Multiple Access) 3Gmobile- systems use OVSF (Orthogonal Variable Spreading Factor) code as channel codes. There are real time services and non-real time services in the 3G mobile-systems. This study develops a real time services friendly method to assign OVSF codes. We try to handle real time services and non-real time services differently by assigning different priority to each kind of services. In fact, we attempt to reduce the number of reassignment of real-time services by assigning high priority to real-time services. The code-reassignment is performed under the following two considerations: 1. Reduce the number of reassignment of real-time service to ensure the QoS (Quality of Service); 2. Make more high-priority calls to be accepted.
While the mobile system tries to reassign channel codes, it chooses a sub tree with minimum priority and minimum number of the busy codes to reassign. If the sub tree with the minimum priority doesn’t have minimum number of busy code, we also reassign the busy codes under the condition of that its BC (number of busy codes) - min BC (minimum number of busy codes) is less than the threshold (h ). Moreover, the proposed method involves a code-reserving mechanism to increase the number of accepted high-priority calls. The simulation illustrate the performance in terms of number of total accept calls, number of reassignment, number of rejected calls, and number of cumulative reassignment of the same code. The simulation result shows that the PRCA_D1(PRCA ： Priority and Reservation based OVSF Code Assignment；D：Down)of the five proposed methods outperform DCA (Dynamic Code Assignment) [13] and others.
Keywords : Quality of Service (QoS), Code Reassignment, Dynamic Code Assignment (DCA), Orthogonal Variable Spreading Factor(OVSF) code, Wideband Code Division Multiple Access (W-CDMA)
Table of Contents
封面內頁 簽名頁 授權書1 ... iii 授權書2 ...iv 中 文摘要...v 英文摘要... vii 誌
謝...ix 目錄...x 圖目 錄... xiii 1. 緒論...1 1.1 緒
論...1 2. 背景知識與已知OVSF 碼的配置與重置機制...5 2.1 背 景知識...5 2.1.1 正交可變展頻因子碼...5 2.1.2 正交可變展 頻因子碼的正交特性...6 2.1.3 碼的阻斷（code-blocking）問題...7 2.1.4 正交可 變展頻因子碼樹的碎裂...8 2.2 已知OVSF 碼的配置與重置機制...9 2.2.1 配 置機制...9 2.2.1.1 隨機分派（Random Code Assignment） ...9 2.2.1.2 先符 合先派（First Fit Code Assignment） ...10 2.2.1.3 擁擠先派（Crowed-First Assignment）...11 2.2.2 重置機制...11 2.2.2.1 DCA 機制的演算法...12 2.2.2.2 DCA 機制 的最小成本搜尋方式...12 2.2.2.3 DCA 機制重置例子...14 3. 本篇論文的作 法...16 3.1 本論文提出的改善策略...16 3.1.1 容量保留機 制...16 3.1.2 最小優先權搜尋機制...17 3.1.3 動態優先權調整機 制...18 3.1.4 系統中的資料型態使用者降速機制...18 3.1.5 新進資料型態使 用者降速機制...19 3.1.6 已被降速的資料型態使用者再升速機制...19 3.2 本論文提 出的五種方法...21 3.3 本論文所提方法之演算法...23 3.4 本論文所 提方法之流程圖...27 3.4.1 PRCA_Fix 的流程圖...27 3.4.2
PRCA_Dyn 的流程圖...29 3.4.3 PRCA_D1 的流程圖...30 3.4.4 PRCA_D2 的流程圖...31 3.4.5 PRCA_D3 的流程圖...32 4. 模擬與 效能分析...33 4.1 模擬的環境和參數...33 4.2 模擬結果和分 析...35 4.2.1 動態保留機制與固定保留機制的影響...35 4.2.2 降系統中資 料型態使用者速率時機...43 4.2.3 調升資料型態使用者速率與未調升速率效能比較...46 4.2.4 負載變化起伏環境與穩定負載環境之比較...49 4.2.5 DCA 機制與本論文所提五種方法其中四種方法 效能比較...51 5. 結論...66 參考文
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