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Service oriented architecture has been proposed to support collaborations among distributed wireless sensor network (WSN) applications in an open dynamic environment. However, WSNs are resource constraint, and have limited computation abilities, limited communication bandwidth and especially limited energy. Fortunately, sensor nodes in WSNs are usually deployed redundantly, which brings the opportunity to adopt a sleep schedule for balanced energy consumption to extend the network lifetime. Due to miniaturization and energy efficiency, one sensor node can integrate several sense units and support a variety of services. Traditional sleep schedule considers only the constraints from the sensor nodes, can be categorized to a one-layer (i.e., node layer) issue. The service oriented WSNs should resolve the energy optimization issue considering the two-layer constraints, i.e., the sensor nodes layer and service layer. Then, the one-layer energy optimization scheme in previous work is not applicable for service oriented WSNs. Hence, in this paper we propose a sleep schedule with a service coverage guarantee in WSNs. Firstly, by considering the redundancy degree on both the service level and the node level, we can get an accurate redundancy degree of one sensor node. Then, we can adopt fuzzy logic to integrate the redundancy degree, reliability and energy to get a sleep factor. Based on the sleep factor, we furthermore propose the sleep mechanism. The case study and simulation evaluations illustrate the capability of our proposed approach. [ABSTRACT FROM AUTHOR]

With the motivation of seamlessly extending wireless sensor networks to the external environment, service-oriented architecture comes up as a promising solution. However, as sensor nodes are failure prone, this consequently renders the whole wireless sensor network to seriously faulty. When a particular node is faulty, the service on it should be migrated into those substitute sensor nodes that are in a normal status. Currently, two kinds of approaches exist to identify the substitute sensor nodes: the most common approach is to prepare redundancy nodes, though the involved tasks such as maintaining redundancy nodes, i.e., relocating the new node, lead to an extra burden on the wireless sensor networks. More recently, other approaches without using redundancy nodes are emerging, and they merely select the substitute nodes in a sensor node's perspective i.e., migrating the service of faulty node to it's nearest sensor node, though usually neglecting the requirements of the application level. Even a few work consider the need of the application level, they perform at packets granularity and don't fit well at service granularity. In this paper, we aim to remove these limitations in the wireless sensor network with the service-oriented architecture. Instead of deploying redundancy nodes, the proposed mechanism replaces the faulty sensor node with consideration of the similarity on the application level, as well as on the sensor level. On the application level, we apply the Bloom Filter for its high efficiency and low space costs. While on the sensor level, we design an objective solution via the coefficient of a variation as an evaluation for choosing the substitute on the sensor level. [ABSTRACT FROM AUTHOR]

Wireless sensor networks (WSNs) are widely used in practice for comprehensively monitoring and gathering physical information via a multitude of sensors. As the development of WSNs, the integration of them with the external Internet is a urgent need. By wrapping the sensor functionality as a WSN service, the Web service is considered as the most promising technology to incorporate WSNs into the Internet. The quest for selecting the service with the best performance promotes service ranking technology. However, due to the dynamic WSN environment, traditional quality of service (QoS) based ranking approaches for general Web services are no longer suitable for the WSN service. In this article, in order to fit the characteristics of the WSN environment, we propose a context-aware WSN service ranking approach by aggregating the user rating and WSN service context. First, the User QoS Assessment(UQA) and Context QoS Assessment(CQA) are proposed, respectively. Then, through the performance influence on the WSN service by the variations in their context, a Fuzzy mechanism is further developed to aggregate the UQA and the CQA. Finally, the experiments are presented to confirm the validity of the proposed approach. [ABSTRACT FROM AUTHOR]