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研究生: 楊凱婷
Kai-Ting Yang
論文名稱: 無線行動網路中資料快取與空間查詢之研究
Data Cache and Spatial Query Techniques in Mobile Wireless Networks
指導教授: 邱舉明
Ge-Ming Chiu
口試委員: 吳秀陽
Shiow-yang Wu
楊竹星
Chu-Sing Yang
陳裕賢
Yuh-Shyan Chen
李育杰
Yuh-Jye Lee
陳秋華
Chyou-Hwa Chen
金台齡
Tai-Lin Chin
學位類別: 博士
Doctor
系所名稱: 電資學院 - 資訊工程系
Department of Computer Science and Information Engineering
論文出版年: 2015
畢業學年度: 103
語文別: 英文
論文頁數: 102
中文關鍵詞: 快取分享索引推播資料拉曳空間查詢連續型全員最近k 點查詢道路網路
外文關鍵詞: cache sharing, index push, data pull, spatial query, CAkNN, road networks vi
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  • 隨著無線網路的快速發展與行動裝置的普及,越來越多的使用者採用行動上網的方式來獲取所需的資料。在無線行動網路中,如何讓使用者快速且正確地取得其所需求的資料與資訊,即是一相當重要的關鍵,也是本論文主要的研究議題。在本論文中,我們針對兩類不同的網路環境與資料查詢方式來探討其機制。其一,在行動隨意網路(mobile ad hoc network) 中,資料以快取(cache) 的方式共享,使用者將查詢所得的資料放在自身的快取中,以利後續自身使用或是分享給鄰近節點使用。其二,在無線行動網路中,使用者以自身所在的位置為基礎,進行多種不同的空間查詢(spatial query)。
    在快取共享部分,傳統上都採取兩種不同型態的快取分享技術:推播式(push-based) 與拉曳式(pull-based),然而此兩種方法有各自的優缺點,前者會有主動推播的成本花費,而後者則可能造成資料重複傳送或是等待時間過長等問題。為解決快取共享資料的存取問題,我們提出了混合型的資料共享機制,稱為Pull-based with Piggybacked Push Protocol(簡稱PPP)。此機制可以有效地結合兩種機制的優點,若欲取得的資料儲存在鄰近節點的快取中,使用者能利用拉曳式技術獲取該資料;此外,採用挾帶(piggyback) 的推播方式,同時將資料儲存的消息傳送給鄰近節點周知,以利後續分享使用。此機制能有效地提昇資料查詢節點附近,快取共享的效能,且降低使用者的等待時間。
    第二項研究議題,與近年來相當熱門的以位置為基礎的服務(Location-Based Service, LBS) 息息相關。在LBS 服務中,最大宗的莫過於以使用者位置為中心,所進行的多種空間查詢,如最近k 點查詢、範圍查詢等等。論文中主要探討較為複雜的,連續型全員最近k 點查詢問題(continuous all k-nearest neighbor query, CAkNN query)。所謂CAkNN 查詢,即是網路中所有的使用者都參與kNN 的查詢,每個點本身既是查詢者也是被查詢者,且持續地想知道自身最即時的kNN查詢結果。我們提出了以bucket PR quadtree 為基礎的結構,利用該結構的特點,可以快速地找出各節點的kNN 結果;此外,論文中提出兩種找尋反向最近k點(reverse k-nearest neighbor, RkNN) 的機制,能在節點移動時,有效率地找出受影響的其他節點,進而快速更新其kNN 查詢結果。模擬結果顯示我們的方法大幅地提昇了無線網路中資料共享與連續型全員最近k點查詢的整體效能。
    最後,我們將CAkNN 查詢議題延伸至道路網路。道路網路由於路段的特性,其較上述一般平面網路擁有較多限制,計算方式也有所不同。除了運用前項研究的基礎,論文中亦提出多樣策略與理論,可有效幫助在道路網路中實現CAkNN查詢,且降低查詢所需的計算量。


    Recent advance of wireless communication and easy availability of mobile devices had fueled the huge amount of data access demands among mobile users. Essentially, accessing the required data or information is the ultimate goal of a mobile users in a wireless environment. In this dissertation, we conduct research on the data access issues in two different domains and propose some related techniques to facilitate the process.
    First, we study the cache sharing issue in a mobile ad hoc network (MANET). Cache sharing has been a popular technique used to support data access in mobile network environments. Existing methods generally resort to two kinds of techniques, push-based and pull-based. The push-based techniques suffer from the proactive advertising cost whereas the pull-based techniques may result in high response latency or redundant data copies. The key to cache sharing is to knowing the whereabouts of a nearby caching site and the
    data it possessed.
    In this dissertation, we propose a cache sharing protocol, called Pull with Piggybacked Push (PPP), in a MANET environment. PPP is unique in that it completely exploits data request broadcasts by performing data pull and index push operations together. In this manner, it retains the advantages of both techniques: performance and communication overhead. With data-pull packet, PPP fully utilizes the cache contents within its zone and delivers index-push information with virtually no overhead.
    Second, this dissertation considers the location-based spatial query processing in a mobile environment. We investigate the continuous all k-nearest neighbor (CAkNN) query, which is a spatial query that continuously monitors kNN results for all mobile users in the network for a specified period of time. This problem is distinguished by the fact that a single movement of a node may result in that several nodes have to recompute their kNN results, which are the moving node itself and its Reverse k-Nearest Neighbor (RkNN) nodes at both the previous and the new locations.
    In this dissertation, we adopt the bucket point-region quadtree as the indexing structure for mobile users. The maintenance of a quadtree is simple and can be localized to the vicinity of the moving node of concern. Besides, the structure helps a node to quickly determine an appropriate search radius, which is crucial for finding/verifying the kNN result. Moreover, we propose two novel RkNN techniques, coined MaxPd and QuadPd, that are tailored for the quadtree structure. These RkNN techniques enable us to integrate the kNN and RkNN searching operations together so as to facilitate the query process. Based on the notion of maximum prune distance, we present two algorithms in order to offer true continuity for a CAkNN query.
    With the basis of above research effort, we further extend the CAkNN query problem into a road network. This dissertation proposes some strategies and theorems to facilitate the query processing among such network-constrained environment.

    1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1 Data Cache in MANET . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Spatial Query . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.3 Objectives of the Dissertation . . . . . . . . . . . . . . . . . . . . . . . . 6 1.4 Thesis Contributions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 1.5 Organization of the Thesis . . . . . . . . . . . . . . . . . . . . . . . . . 9 2 Related Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2.1 Data Cache and Cache Sharing in MANET . . . . . . . . . . . . . . . . 10 2.2 Spatial Query in Mobile Environment . . . . . . . . . . . . . . . . . . . 14 3 Pull-Based with Piggybacked Push Scheme for Cache Sharing . . . . . . . . . 19 3.1 System Model and Problem Formulation . . . . . . . . . . . . . . . . . . 19 3.2 Pull with Piggybacked Push (PPP) Protocol . . . . . . . . . . . . . . . . 20 3.2.1 Data Access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 3.2.2 Index Push and IV Update . . . . . . . . . . . . . . . . . . . . . 24 3.2.3 Cache Replacement . . . . . . . . . . . . . . . . . . . . . . . . . 25 3.3 Performance Evaluation of Cache Sharing Protocol . . . . . . . . . . . . 30 3.3.1 Simulation Setup . . . . . . . . . . . . . . . . . . . . . . . . . . 30 3.3.2 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . . 33 3.4 Discussion of Related Issues . . . . . . . . . . . . . . . . . . . . . . . . 48 3.4.1 Data Structure for Caching Information . . . . . . . . . . . . . . 48 3.4.2 Interplay with Routing Protocol . . . . . . . . . . . . . . . . . . 50 4 Continuous All k-Nearest Neighbor Query in Mobile Environment . . . . . . . 52 4.1 Network Model and Problem Formulation . . . . . . . . . . . . . . . . . 53 4.2 The Proposed Scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 4.2.1 Bucket PR Quadtree Structure for CAkNN . . . . . . . . . . . . 55 4.2.2 kNN Update . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 4.2.3 RkNN Search . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 4.3 Performance Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 4.3.1 Performance Analysis . . . . . . . . . . . . . . . . . . . . . . . 65 4.3.2 Simulation Setup . . . . . . . . . . . . . . . . . . . . . . . . . . 67 4.3.3 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . . 69 5 Continuous All k-Nearest Neighbor Query over Road Networks . . . . . . . . . 83 5.1 Network Model and Problem Formulation . . . . . . . . . . . . . . . . . 83 5.2 CAkNN Processing over Road Networks . . . . . . . . . . . . . . . . . . 86 5.2.1 kNN Update over Road Networks . . . . . . . . . . . . . . . . . 87 5.2.2 RkNN Search over Road Networks . . . . . . . . . . . . . . . . 91 6 Summary and Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

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