In view of the relative positioning problem between non-regular quadrilateral grids and regular rectangle grid nodes in the wave front construction method, concrete realization problems with four grid positioning meth...In view of the relative positioning problem between non-regular quadrilateral grids and regular rectangle grid nodes in the wave front construction method, concrete realization problems with four grid positioning methods （vector cross product judgment, angle sum, intersection-point, and signs comparison algorithms） in wave front construction which are commonly used in computer graphics are compared and analyzed in this paper. Based on the stability analysis of the location method, the calculation examples show that the vector cross product judgment method is faster and more accurate than other methods in the realization of the relative positioning between non-regular quadrilateral grids and regular rectangle grid nodes in wave front construction. It provides precise grid point attribute values for the next steps of migration and demigration.展开更多
An ad hoc network is a group of wireless mobile computers(or nodes),in which individual nodes cooperate by forwarding packets for each other to allow nodes to communicate beyond direct wireless transmission range.Beca...An ad hoc network is a group of wireless mobile computers(or nodes),in which individual nodes cooperate by forwarding packets for each other to allow nodes to communicate beyond direct wireless transmission range.Because of node mobility and power limitations,the network topology changes frequently.Routing protocol plays an important role in the ad hoc network.A recent trend in ad hoc network routing is the reactive on-demand philosophy where routes are established only when required.As an optimization for the current Dynamic Source Routing Protocol,a secure and pragmatic routes selection scheme based on Reputation Systems was proposed.We design the Secure and Pragmatic Routing protocol and implement simulation models using GloMoSim.Simulation results show that the Secure and Pragmatic Routing protocol provides better experimental results on packet delivery ratio,power consumption and system throughput than Dynamic Source Routing Protocol.展开更多
In order to avoid internal attacks during data aggregation in wireless sensor networks, a grid-based network architecture fit for monitoring is designed and the algorithms for network division, initialization and grid...In order to avoid internal attacks during data aggregation in wireless sensor networks, a grid-based network architecture fit for monitoring is designed and the algorithms for network division, initialization and grid tree construction are presented. The characteristics of on-off attacks are first studied and monitoring mechanisms are then designed for sensor nodes. A Fast Detection and Slow Recovery (FDSR) algorithm is proposed to prevent on-off attacks by observing the behaviors of the nodes and computing reputations. A recovery mechanism is designed to isolate malicious nodes by identifying the new roles of nodes and updating the grid tree. In the experiments, some situations of on-off attacks are simulated and the results are compared with other approaches. The experimental results indicate that our approach can detect malicious nodes effectively and guarantee secure data aggregation with acceptable energy consumption.展开更多
基金This research work is supported by the Projects of National Science Foundation of China （Grant No, 40574052 and 40437018） and National Basic Research Program of China （973 Program） （Grant No. 2007CB209603）.Acknowledgements We wish to thank Researcher Xu Tao for his advice and comment. We also thank Mrs. Wang Kun for her help in the process of translation.
文摘In view of the relative positioning problem between non-regular quadrilateral grids and regular rectangle grid nodes in the wave front construction method, concrete realization problems with four grid positioning methods （vector cross product judgment, angle sum, intersection-point, and signs comparison algorithms） in wave front construction which are commonly used in computer graphics are compared and analyzed in this paper. Based on the stability analysis of the location method, the calculation examples show that the vector cross product judgment method is faster and more accurate than other methods in the realization of the relative positioning between non-regular quadrilateral grids and regular rectangle grid nodes in wave front construction. It provides precise grid point attribute values for the next steps of migration and demigration.
基金The National Natural Science Foundation of China (No.60403027)
文摘An ad hoc network is a group of wireless mobile computers(or nodes),in which individual nodes cooperate by forwarding packets for each other to allow nodes to communicate beyond direct wireless transmission range.Because of node mobility and power limitations,the network topology changes frequently.Routing protocol plays an important role in the ad hoc network.A recent trend in ad hoc network routing is the reactive on-demand philosophy where routes are established only when required.As an optimization for the current Dynamic Source Routing Protocol,a secure and pragmatic routes selection scheme based on Reputation Systems was proposed.We design the Secure and Pragmatic Routing protocol and implement simulation models using GloMoSim.Simulation results show that the Secure and Pragmatic Routing protocol provides better experimental results on packet delivery ratio,power consumption and system throughput than Dynamic Source Routing Protocol.
基金This work was supported by the National Natural Science Foundation of China under Grant No. 60873199.
文摘In order to avoid internal attacks during data aggregation in wireless sensor networks, a grid-based network architecture fit for monitoring is designed and the algorithms for network division, initialization and grid tree construction are presented. The characteristics of on-off attacks are first studied and monitoring mechanisms are then designed for sensor nodes. A Fast Detection and Slow Recovery (FDSR) algorithm is proposed to prevent on-off attacks by observing the behaviors of the nodes and computing reputations. A recovery mechanism is designed to isolate malicious nodes by identifying the new roles of nodes and updating the grid tree. In the experiments, some situations of on-off attacks are simulated and the results are compared with other approaches. The experimental results indicate that our approach can detect malicious nodes effectively and guarantee secure data aggregation with acceptable energy consumption.
