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In a large-scale wireless sensor network, a topology is needed to gather state-based data from sensor network and efficiently aggregate the data given the requirements of balanced load, minimal energy consumption, and prolonged network lifetime. In this study, we proposed a ring-based hierarchical clustering scheme (RHC) consisting of four phases: predeployment, parent-child relationship building, deployment, and member join phases. Two node types are distributed throughout the network: cluster head nodes (type 1 node) and general sensor nodes (type 2 node). The type 1 node has better battery life, software capability, and hardware features than the type 2 node; therefore, the type 1 node is a better cluster head than type 2 node. Due to our IP naming rules and type 1 nodes as cluster heads, public key cryptography, such as RSA (Rivest, Shamir, Adleman), or ECC (Elliptic Curve Cryptosystem), is easily implanted to our system to strengthen our security. The sink node is the only certification authority in our system, but n level cluster heads can be extended to n level certification authorities if needed, where n is maximum number of level.

Most routing protocols focus on obtaining a workable route without considering network traffic condition for a mobile ad hoc network (MANET). Therefore, the quality of service (QoS) is not easily achieved by the real time or multimedia applications. To support QoS, this work proposes a QoS-aware routing protocol that incorporates an admission control scheme into route discovery and route setup. A dual-card dual-signal mechanism is adopted to increase system performance. Simulation results show the proposed protocol can more significantly improve packet delivery ratio, throughput (in heavy load), as well as reduce average end-to-end delay than routing protocols without QoS support can.

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On the basis of the energy distribution of eigenimages of an image, a new watermark attacking method is proposed. For most removal attacking methods, they regard watermark as noise and adopt denoising methods to remove watermark. However, when the energy of watermark is removed from a watermarked image, the energy of the original image is also removed at the same time. To solve this problem, we predict the watermark energy using just-noticeabledistortion (JND). Then remove watermark energy from watermarked image based on the characteristic of eigen-images. From the experiment results, the proposed method is a very effective watermark attacking method.