普及運算（ubiquitous computing）被視為下一代的電腦運算技術，其願景是讓使用者可以在任何時間、任何地點、透過任何裝置來存取運算環境。近年來，許多研究成果使得普及運算技術有長足的進步。然而，在資源有限的普及網路（ubiquitous networks）中仍然有一些尚待解決或改善的議題。本論文將針對資源有限的普及網路環境來探討三個重要的研究議題，包含路由協定、網路安全、與服務自動化。
首先，我們處理在網路層上如何有效利用能源的議題。由於普及網路中有許多裝置（例如，感測節點與手持式裝置）是以電池供電，因此如何有效利用能源是一個相當重要的議題。在本論文中，所提出的能源比例式路由方法（Energy Proportional Routing，ERP）與封包長度調適方法（Packet Length Adaptation，PLA）可以有效地提升叢聚式無線網路的網路吞吐量與能源使用率。為了平衡負載，EPR 預測並控制所有節點的能源損耗以讓所有節點的能源使用率能夠趨於平均能源使用率。另外，PLA 可以根據雜訊所造成的封包錯誤率來設定最佳的封包長度以提升網路吞吐量與能源使用率。然而，隨著雜訊的增強就如同拉長傳輸距離一樣會造成更多的能源損耗。因此，為了能夠更準確的估算能源損耗，本論文也提出一個將通道雜訊轉換為傳送距離的模型使得在加入通道雜訊的情況下亦能夠有效地提升網路吞吐量與能源使用率。
第二個要探討的議題是普及網路的安全性。由於個人資料可能會透過普及網路來傳送，因此驗證資料的來源與完整性是一項必要的工作。然而，傳統的安全性方法並無法直接套用在以降低能源損耗為重要議題的網路環境上。因此，本論文提出了適用於叢聚式無線網路的認證式入侵預防機制（Authentication-based Intrusion Prevention，AIP）與協同式入侵偵測機制（Collaboration-based Intrusion Detection，CID）。AIP 依據資料重要性、網路頻寬、金鑰雜湊訊息認證碼長度、與金鑰存活期等特性而採用安全性等級不同的認證機制以達到降低能源損耗的目的。然而，AIP 並無法避免被入侵的內部節點所發動的攻擊。因此，CID 藉由網路節點互相監控的方式來進行入侵偵測以在網路安全與能源損耗之間取得平衡。
最後要探討的是考量服務品質要求與資源使用率的服務自動化議題。對使用者所要求的普及服務（ubiquitous services）而言，一組適合的裝置應該能夠自動地形成一個小型網路（piconet）以執行這些普及服務而不需要使用者的介入。為了達到此目的，首先我們分別提出了用來描述普及服務與普及網路的數學模型。另外，由於不同的服務型態與使用者對於服務品質的定義有很大的差異，因此多目的效益函數理論（Multiple Objective Utility Theory）被用來量化使用者對於服務品質的滿意度。本論文提出了兩個服務自動化演算法。對於移動式且大型普及網路而言，我們提出了基於解決有類別限制之子圖同構問題（Class Constrained Subgraph Isomorphism Problem）的分散式服務自動化演算法。另一方面，對於固定式且小型普及網路而言，我們則是提出了基於解決多維度多選擇背包問題（Multi-dimension Multi-choice Knapsack Problem）的集中式服務自動化演算法。透過實驗與模擬可以證明本論文所提出的兩個演算法可以在資源有限的普及網路中有效地配置網路資源並取得代表服務品質之系統效益值的近似最佳解。

Ubiquitous computing (UbiCom) is the next-generation computing technology with the vision: user could access computing environments in an “any time, any where, any device” manner. In the latest decades, the researches on UbiCom have significantly improved to realize digital life. However, there are still several open issues in resource-constrained ubiquitous networks (UbiNet). In this dissertation, we will study three important issues in resource-constrained UbiNet, including routing protocol, network security, and service automation.
First, this work tackles the energy-efficiency issue at the network layer. Energy conservation is truly critical in UbiCom since there are a lot of battery-powered devices (e.g., sensor node, handheld device) in UbiNet. In this dissertation, Energy Proportional Routing (EPR) and Packet Length Adaptation (PLA) are proposed to maximize the throughput and energy utilization in cluster-based wireless networks. To balance the load, EPR algorithm predicts and controls the energy consumption of each node as close as possible to the threshold representing the energy utilization mean value among clusters. In addition, PLA is derived and developed to optimize the throughput and energy utilization in wireless networks. However, more noise introduces more energy consumption since the noise is equivalently regarded as lengthening of transmission distances. Thus, a noise-referred distance model of wireless channels is also developed for more accurate estimation of the dissipated proportion in the residual energy so that further improvement of throughput and energy utilization is obtained.
The second research issue is the network security. Since the personal information could be forwarded in UbiNet, verifying authenticity and integrity of delivered data is indispensable. Unfortunately, energy-efficiency is not considered in conventional security measures. In this dissertation, two energy-efficient security approaches are proposed. In Authentication-based Intrusion Prevention approach (AIP), distinct authentication mechanisms with different security levels are introduced to verify the data according to their relative importance so that the energy consumption is efficient reduced. However, the security threat from compromised sensor nodes cannot be fully avoided. Thus, Collaboration-based Intrusion Detection approach (CID) is then proposed. In CID, the nodes collaboratively monitor each other to balance the tradeoff between network security and energy efficiency.
Finally, we study the issue of service automation with considering quality of service (QoS) and resource utilization. For each ubiquitous service (UbiServ), a set of adequate devices in UbiNet could be automatically organized to carry out this requested UbiServ without any user interaction. For this purpose, the Service Profile (SP) and Ubiquitous Network (UN) models are proposed to represent the UbiServ and the UbiNet, respectively. Moreover, the Multiple Objective Utility Theory (MUOT) is adopted to quantify the service quality which depends on the types of UbiServ and user-specified QoS needs. In this dissertation, two service automation algorithms are proposed. For mobile and large scale networks, the distributed service automation algorithm is proposed on the basis of solving Constrained Subgraph Isomorphism Problem (CC-SUBISO). On the other hand, for fixed and small scale networks, the centralized service automation algorithm is proposed on the basis of solving Multi-dimension Multi-choice Knapsack Problem (MMKP). The experiments and network simulations fully support that the proposed algorithms could maximize the service utility by efficiently allocating the network resources in resource-constrained UbiNet.

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