Catálogo de publicaciones - libros

Web information system should be considered due to its performance for real-time application with different types of mobile agents serviced by different mobile communication operators. The ubiquitous Web information server accessed by a user-group with various mobile agents should be considered as a unified center for real-time unified-and-ubiquitous Web information services. We studied the performance of Web information access, i.e. registration and retrieval, with intelligent mobile agents for real-time ubiquitous-unified Web information services. Based on our empirical results collected from a test-bed trial service we have determined that real-time ubiquitous-unified Web information services may be applicable to various applications with intelligent mobile agents, e.g. real-time ubiquitous-healthcare service.

There are many schemes to increase energy efficiency in wireless sensor network as energy is precious resource. We focus on improving energy efficiency in sensing module while most of the previous works focus on the energy saving in communication module. When a sensor network continuously senses wide area, energy consumption is needed largely in sensing module. We consider a change rate of sensed data and adjust sensing period to reduce energy consumption while minimizing average delay between change of field and detection. Additionally, cooperation among neighbor nodes is essential to reduce energy consumption and the delay. Our dynamic sensing algorithm reduces the energy consumption and delay between change of field and detection. Our scheme controls sensing cycle based on change of sensing data and sensing cycle of neighbor nodes. It improves energy efficiency up to 90%, and reduces the delay up to 84%, comparing to the previous works.

Most of the sensor networks use a symmetric protocol since sensor networks are comprised of sensor nodes with restricted hardware. Sensor networks with symmetric cryptography contain a global key stored on each sensor node and may be deployed in a hostile environment. When sensors nodes are compromised, an attacker can inject false sensing reports or false Message Authentication Codes into a legitimate report. A probabilistic voting-based filtering scheme has been proposed to combat these threats from compromised nodes. However, this scheme has the problem that it cannot re-establish a session key when some nodes of the source cluster or some intermediate cluster head have been compromised. The scheme cannot also control the position of verification nodes to minimize energy consumption as topology changes. Therefore, we propose a fuzzy-based en-route filtering scheme to deal with these problems. Through performance analysis and simulation, our result shows that the proposed scheme is much more efficient than the probabilistic voting-based scheme in many cases.

A general web-based distance system uses video data and audio data to provide synchronize between teacher and student. This paper presents the design and implementation of an error and an application program sharing agent for collaborative multimedia distance education system which is running on RCSM (Reconfigurable Context Sensitive Middleware) for ubiquitous networks. RCSM provides standardized communication protocols to interoperate an application with others under dynamically changing situations. It describes a hybrid software architecture that is running on situation-aware middleware for a web based distance education system which has an object with an various information for each session. There are two approaches to software architecture on which distributed, collaborative applications are based. Those include CACV (Centralized-Abstraction and Centralized-View) and RARV (Replicated-Abstraction and Replicated-View). And it also supports an application sharing model with fault tolerance for multimedia distance education system based RCSM.

Energy efficiency is a primary problem in wireless sensor networks which employ a large number of intelligent sensor nodes to accomplish complicated tasks. Focused on the energy consumption problem in target tracking applications, this paper proposes a dynamic energy management mechanism with an improved particle filter prediction in wireless sensor networks. The standard particle filter is improved by combining the radial-basis function network to construct the process model and the novel algorithm is adopted to predict the prior position of target. For dynamic awakening, the idle interval of each sensor node is estimated according to its sensing tasks. A cluster head rotating approach is introduced from low-energy adaptive clustering hierarchy for collecting data through the large sensing field. A group of sensor nodes which are located in the vicinity of target will wake up and have the opportunity to report their data. Distributed genetic algorithm is performed on cluster heads to optimize the sensor node selection. In target tracking simulations, we verify that the improved particle filter has more robustness than standard particle filter against the sensing error and dynamic energy management enhances energy efficiency of wireless sensor networks.

The dynamic en-route filtering scheme (DEF) proposed by Yu and Guan was designed to detect and drop false reports in wireless sensor networks. In this scheme the choice of a threshold value that limits the key dissemination is important since it represents a trade-off between detection power and overhead. A large threshold value increases the probability of detecting false reports but it consumes too much energy in the key dissemination phase. Thus, we should choose a threshold value such that it provides sufficient detection power, while consumes energy effectively. In this paper we propose a key dissemination limiting method for DEF. The threshold value to limit the key dissemination is determined by a fuzzy rule-based system with consideration of the energy level of the network, the number of keys in a cluster, and the distance from the base station (BS) to that cluster. The simulation results show that the proposed method can conserve energy, while it provides sufficient detection power.

There are many application areas of wireless sensor networks, such as combat field surveillance, terrorist tracking and highway traffic monitoring. These applications collect sensed data from sensor nodes to monitor events in the territory of interest. One of the important issues in these applications is the existence of the radio-jamming zone between source nodes and the base station. Depending on the routing protocol the transmission of the sensed data may not be delivered to the base station. To solve this problem we propose a genetic algorithm based routing method for reliable transmission while considering the balanced energy depletion of the sensor nodes. The genetic algorithm finds an efficient routing path by considering the radio-jamming zone, transmission distance, average remaining energy and hop count. In simulation, our proposed method is compared with LEACH and Hierarchical PEGASIS. The simulation results show that the proposed method is efficient in both the energy consumption and success ratio of delivery.

With the developments of computer and wireless communication technology, wireless sensor networks have broad application prospects in more and more fields. But sensor nodes are usually powered by a small size and limited battery. In this paper, we propose an pheromone based energy-aware directed diffusion algorithm(PEADD) for sensor networks. The algorithm uses pheromone of ants to improve the energy module in directed diffusion algorithm. The method has been implemented and performed experiments NS2. Our experimental results show the new algorithm extends the network lifetime and characteristics of our method. In the end, the future research directions are discussed.

Dynamic deployment is one of the key topics addressed in wireless sensor networks (WSNs) study, which refers to coverage and detection probability of WSNs. This paper proposes a self-organizing algorithm for enhancing the coverage and detection probability for WSNs which consist of mobile and stationary nodes, which is so-called virtual force-directed particle swarm optimization (VFPSO). The proposed algorithm combines the virtual force (VF) algorithm with particle swarm optimization (PSO), where VF uses a judicious combination of attractive and repulsive forces to determine virtual motion paths and the rate of movement for sensors and PSO is suitable for solving multi-dimension function optimization in continuous space. In VFPSO, the velocity of each particle is updated according to not only the historical local and global optimal solutions but also the virtual forces of sensor nodes. Simulation results demonstrate that the proposed VFPSO has better performance on regional convergence and global searching than PSO algorithm and can implement dynamic deployment of WSNs more efficiently and rapidly.

This paper is concerned with designing of a multirate controller over a network in which a sensor node transmits data to the controller node only if its measurement value changes more than a given specified value. When the send-on-delta transmission method is used, it is not ensured that the controller node receives data from the sensor nodes regularly at every control updating period. We thus propose a modified Kalman filter in which states of the plant are regularly estimated even if there is no sensor data reception. An optimal LQG controller is then designed in order to minimize the quadratic cost function of state and control effort. By providing the upper and lower bounds of the cost function, we prove that the proposed multirate controller is stable with the given value, which is a trade-off parameter between control performance and data transmission rate. Through numerical simulations, we demonstrate the feasibility and the usefulness of the proposed control method.