结构化P2P网络资源搜索Chord算法研究与改进方案

针对结构化P2P网络资源搜索技术中Chord算法进行深入研究和分析,分别从路由信息冗余、节点延迟划分、查询路径判断等3个方面对传统Chord系统进行讨论和改进,提出了相应的改进方案,并通过仿真实验对方案进行性能测试和验证分析,证明改进方案减少了资源查询路径长度,降低了信息的转发次数,减轻了网络的负担,从而能更好提高资源搜索效率。

Graph-based single-copy routing in delay tolerant networks

This paper presents a new graph-based single-copy routmg method m delay tolerant networks （DTN）. With time goes on in the networks, a DTN connectivity graph is constituted with mobility of nodes and communication, and a corresponding greedy tree is obtained using a greedy algorithm in DTN connectivity graph. While there are some bad nodes such as disabled nodes or selfish nodes in delay tolerant networks, the nodes can choose the next p^oper intermediate node to transmit the mes- sage by comparing the location of neighboring nodes in the greedy tree. The single-copy routing method is very appropriate for energy-constrained, storage-constrained and bandwidth-constrained applications such as mobile wireless DTN networks. We show that delivery ratio is increased significantly by using the graph-based single-copy routing when bad nodes exist.

Topology inference of uncertain complex dynamical networks and its applications in hidden nodes detection

The topological structure of a complex dynamical network plays a vital role in determining the network＇s evolutionary mecha- nisms and functional behaviors, thus recognizing and inferring the network structure is of both theoretical and practical signif- icance. Although various approaches have been proposed to estimate network topologies, many are not well established to the noisy nature of network dynamics and ubiquity of transmission delay among network individuals. This paper focuses on to- pology inference of uncertain complex dynamical networks. An auxiliary network is constructed and an adaptive scheme is proposed to track topological parameters. It is noteworthy that the considered network model is supposed to contain practical stochastic perturbations, and noisy observations are taken as control inputs of the constructed auxiliary network. In particular, the control technique can be further employed to locate hidden sources （or latent variables） in networks. Numerical examples are provided to illustrate the effectiveness of the proposed scheme. In addition, the impact of coupling strength and coupling delay on identification performance is assessed. The proposed scheme provides engineers with a convenient approach to infer topologies of general complex dynamical networks and locate hidden sources, and the detailed performance evaluation can further facilitate practical circuit design.

Reasonable routing in delay/disruption tolerant networks

Delay/disruption tolerant networking （DTN） is an approach to networking where intermittent connectivity exists： it is often afforded by a store and forward technique. Depending on the capability of intermediary nodes to carry and forward messages, messages can be eventually delivered to their destination by mobile nodes with an appropriate routing protocol. To have achieved a successful delivery, most DTN routing protocols use message duplication methods. Although messages are rapidly transferred to the destination, the redundancy in the number of message copies increases rapidly. This paper presents a new routing scheme based on a stochastic process for epidemic routing. Message redundancy is efficiently reduced and the number of message copies is controlled reasonably. During the contact process of nodes in the network, the number of message copies changes, and according to the variability in the number of copies, we construct a special Markov chain, birth and death process, on the number of message copies then calculate and obtain a stationary distribution of the birth and death process. Comparing the theoretical model with the simulation we have performed we see similar results. Our method improves on time-to-live （TTL） and antipacket methods, in both redundancy and delivery success efficiency.