行動視訊偵搜隨意網路中涵蓋視訊連結建立與保持之研究

Abstract

自從美國紐約911事件後，個人與公眾安全的重要性備受矚目，視訊偵搜系統已廣泛使用於保護人身與公共安全的應用上。隨著以IP為基礎的偵搜網路興起，視訊影像資料可以透過無線網路傳輸，因此激發了更多新型態的行動式視訊偵搜服務。例如將數位相機裝置在行動設備上(例如筆記型電腦，PDA，3G行動電話等)所構成的監視系統，這使得偵搜服務有更大的機動性。 本論文的主要研究目的是當偵搜取像目標不在網路涵蓋範圍內時，指揮移動節點，以花費最少的移動能量來建立視訊連結涵蓋偵搜取像目標，提供目標視訊給取像需求端，並在當偵搜取像目標移動造成原來視訊連結中斷時，保持偵搜取像與取像需求端之間的視訊連結。 為了能夠指揮移動節點與感測目標移動，本論文參考廖佑楷與張家瑋等的網路功能堆疊(function stack)架構，在應用層新增兩個指令功能方塊設計：指揮命令功能方塊、感測移動功能方塊，來規畫移動路徑以涵蓋偵搜取像目標，並依據目標移動資訊下達任務指令，以指揮各節點移動或進行任務換手來保持視訊連結的完整。 對規畫移動路徑以建立涵蓋偵搜取像目標的視訊連結問題，本論文首先建立初始涵蓋視訊連結問題(Initial Coverage and Connection Problem, ICCP)數學模型以減少移動能量消耗為目的，考量通訊範圍與移動路徑的限制(避開障礙物)，來決定配置節點的個數、位置與配對關係變數。我們設計了列舉配置節點法與配對演算法的二階段求解演算法(Two-Stage Solution Algorithm, TSSA)，來規畫移動路徑以建立涵蓋偵搜取像與取像需求端之間的視訊連結。 針對當目標移動時保持視訊連結不中斷的問題，考慮前瞻一段時間T並預測T時間後目標的位置，規畫節點如何從現有位置移動來對T時間後的目標保持涵蓋並連結，可將此問題視為ICCP問題的延伸。並提出動態調整節點位置的機制，其中包括預測目標移動位置、更新鄰居資訊以進行任務換手、與結合TSSA求解ICCP問題的動態調整節點位置演算法(Dynamic Adjustment Peers Location Algorithm, DAPLA)，以減少移動能量消耗並動態調整節點位置或交接任務來保持視訊連結。 在實作方面，本論文在應用層利用了VB.NET 2003TM和SQL 2000TM簡易的實做移動規畫與指揮機制，其運作流程如下 :(1)設計自身廣播(Broadcast)程式以建立整個網路節點的資訊列表(PIL)，(2)透過LINGO 9.0規畫節點移動位置，並設計指揮命令功能方塊，將位置資訊以單點傳送(unit-cast)的方式傳送給指定的節點，(3)節點收到該封包後，會依照封包內的資訊移動到指定的位置，以協助涵蓋並建立偵搜取像目標與與取像需求端之間的視訊連結。

Since the event of 911 in New York, the importance of individual and public safety has been raised. Video surveillance system has been broadly used in the applications of human and public protection. By the development of IP-based video surveillance network, the transmission of video streaming can be though wireless network, and solicits more new types of mobile video surveillance services. For example, the monitoring system which consists of digital cameras setting on mobile equipments like laptop, PDA, 3G and cellular phone, etc, provides much more mobility of video surveillance service. The goal of this thesis aims at designing the methodology and associated system to command the peers of a mobile video surveillance network to establish a connection covering the target, static or moving, with minimum moving energy consumption and to provide and maintain target’s streaming video to requesting peer. To command peers moving and sense the target moving, we exploit the mobile video surveillance architecture proposed by Liao, 2006, and Chang, 2007, and add two new function blocks to the application layer: command block and surveillance block, We use these two blocks to plan a path to cover the target and to assign the coverage and relay mission to proper peers by moving or handoff based on the movement information of target. To model the problem of path planning for establishing video surveillance coverage and connection, we first formulate a mathematical model of Initial Coverage and Connection Problem (ICCP). The model takes communication coverage and the constraints of moving path into consideration to minimize moving energy consumption. There are three decision variables: (1) numbers of active peers, (2) desired locations of peers and (3) pair variables. We propose a two-stage solution algorithm (TSSA) to solve ICCP. Stage 1 decides numbers of active peers and stage 2 determines the desired locations of the active peers and peer-location assignment. To address the problem about how to maintain a video connection as the target moves, we look ahead T time units and predict target’s next location after T. Then we plan how the peers move to maintain video surveillance coverage and connection when the target is at the predicted location. This problem can be viewed as an extension of ICCP. We propose a mechanism which includes information exchange, mission handoff and Dynamic Adjustment Peers Location Algorithm (DAPLA). The main concepts of the algorithm are repetitively predicting target’s next location, refreshing neighborhood information to do the mission handoff and solving ICCP by TSSA. We implement the mechanism for moving planning and command by VB.NET 2003TM and SQL 2000TM in the application layer in three parts: I. a self-broadcast program to construct the Peers Information list (PIL), II. the TSSA in Lingo 9.0 to solve ICCP for a path plan of peer movements, and III. a surveillance block to sense and predict target location and a command function block to transmit location information to active peers with unit-cast.