在過去的十年中, 隨著無線通訊及積體電路技術的進步，行動計算成為最熱門的研究領域之一。相較傳統環境的研究，此新興的計算應用在無線行動網路中有著新的因素及限制，例如客戶端的移動，行動設備的貧乏電力，有限的無線頻寬，等等. 這些特有的特性給資料庫社群及通訊社群帶來許多新的挑戰，包括位置管理、資料傳輸、行動服務管理等。在本論文，我們探索了一些基礎但是尚未解決的議題。並且在目前存在的行動計算架構下，我們針對這些議題提出有效率的解決方法。

　　在行動管理議題上，過去的研究把焦點放在改善移動運算或是尋找運算兩者之一。我們提出 Cache and Carry (C&C) 策略來同時改進上述兩個運算的效能。我們的方法尤其能成功的將許多廣域通訊運算減少成區域通訊運算。我們的實驗成果顯示 C&C 策略明顯的優於其他策略。

　　我們也解決了在有限頻寬的無線網路下傳送大型資料給行動客戶端的議題。完全複製此大型資料到所有的區域是一個直覺的方法。但是此方法卻不切實際，原因是此方法不僅浪費資源並且因為龐大的傳輸負載而降低整個系統效能。我們分兩個階段解決此問題。我們首先設計一個編碼的方法來將地理上的區域編碼，並且描述此編碼方法的特性。然後，我們提出一個基於動態規劃的方法來有效率的找出行動客戶端最有可能行經的路徑。在客戶端還沒到達這些區域之前，先將大型資料傳送到路徑上的這些區域。實驗結果顯示我們提出來的方法大量改進的完全複製方法的效能。

　　我們也研究在行動服務管理上的服務移動的最佳化議題。我們替行動代理人設計一個行動控制的機制，其中包括了一個要求運算及一個移動運算。接著，我們建立一個機率模型並且推導我們提出來機制的代價函數。根據這些代價函數，行動代理人可以決定出最佳的停留地點來服務行動使用者。我們的效能研究顯示使用我們提出來的機制可以大量的減少通訊代價。另外，我們也討論一些實作此機制上的相關議題，包括重複資料的維護。

　　最後，我們考慮在多頻道資料傳播系統下，一個滿足具時間限制特性的服務的排程問題。無線環境下的具時間限制特性的服務在許多應用中都十分普遍，但是過去的文獻並沒有解決此問題。我們首先探討滿足此種服務的廣播排程必須具備的特性。接著，我們推導要提供此項服務的理論下限值。然後，我們提出一個排程方法可以產生具時間限制特性的服務的廣播節目，並且此廣播節目只使用最少的廣播頻道數量。我們也提供理論的證明來證明排程演算法產生的廣播節目滿足上述所有特性。

　　With the advance of wireless communication and VLSI technologies,the emerging mobile computing becomes one of the most attractive research topics in the past decade.Comparing to the previous research in traditional environments,the novel computing paradigm has new factors and limitations in the wireless mobile network,such as mobility of clients, scarce power of mobile devices,limited bandwidth, $ldots$, etc.These distinctive characters bring many new challenges to the database community and the communication society, including location management, data transmission,mobile service management, $ldots$, etc.In this dissertation, we discover certain fundamental and unsolved issues,and proposed effective solutions to these problems based on the current existing mobile computing architecture.

　　For location management issue, past works focus on improving either the movement operation or the locating operation. We propose the Cache and Carry (C&C) Strategy to improve both of them simultaneously to improve the performance than previous works. In particular, our proposed strategy successfully reduces a lot of global communication operations to local communication operations. Our performance results show that the C&C strategy significantly outperforms the other strategies.

　　We also address the issue of delivering large-size data for mobile users under a limited bandwidth wireless environment. Fully replicating the data over all cells is a straightforward solution, but is impractical because it not only wastes resource but also degrades the overall performance due to heavy communication load. We resolve this problem in two stages. To fast look up the geographic information, we first devise an encoding scheme to encode the geographic cell, and describe useful properties of the encoding scheme. Then, we propose a dynamic-programming based method to efficiently find out those most possibly resided cells to pre-sent large-size data before the mobile user visits. Experimental results reveal that our proposed algorithm dramatically improves the performance.

　　We study the optimization issue of the service mobility for the management of mobile services. A mobility controlling mechanism consisted of the request operation and the movement operation is designed for a mobile agent (MA). Then, we develop a probability model and derive the cost functions for the proposed mechanism.Based on the cost functions, the mobile agent is able to determine a best resident location to serve the roaming mobile user. Performance study shows that communication cost of employing our proposed mechanism is dramatically reduced.In addition, we discuss certain implementation issues about maintaining the duplicate data items in a MA-resident site.

　　Finally, we consider the data scheduling problem for the time-constrained services in the multi-channel data dissemination systems. The time-constrained services are widely used in many applications,but not solved in past related work.We first derive the properties that a broadcast schedule must have in order to satisfy a set of given time constraints. Next, we present a theoretical lower bound on the number of channels for offering the time-constrained services. Then, we propose a scheduling algorithm that owns all the necessary properties and always employs the minimum number of channels. And,the produced schedule always meets the requirement of time constraints of the clients.

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