基于拓扑势加权的动态PPI网络复合物挖掘方法

从动态蛋白质相互作用（PPI）网络中挖掘蛋白质复合物是当前复合物挖掘研究的一个热点,但是目前大都采用未加权网络进行聚类分析,由于不能准确地描述网络的拓扑特性,因此其正确率不高.鉴于此,本文提出采用拓扑势场的方法来构造加权网络,网络中的每一个蛋白质都被视作一个物理粒子,在它周围存在一个虚拟的作用场,由此网络中所有蛋白质的相互作用联合形成一个拓扑势场,文中定义了结点间的拓扑势的概念,并以此来构造加权网络,之后采用马尔科夫聚类算法在DIP数据和Krogan数据上进行复合物挖掘.与其它经典算法相比,该方法的precision和f-measure值较高,能更好地识别蛋白质复合物.     

Concurrent discrete event-driven simulation tools

Parallel processing techniques that may enhance the performance of simulation methods for telecommunications networks are reviewed. The assumption that each processor runs a single network component process is avoided, such a premise being unrealistic when simulating large networks. Performance issues arising from implementing distributed simulation strategies on message-passing processor architectures are discussed. Nontrivial network models are separated into domains, each sited on a distinct transputer. Problems arising from the limited connectivity of the transputer are also addressed     

Message delivery in heterogeneous networks prone to episodic connectivity

We present an efficient message delivery framework, called MeDeHa, which enables communication in an internet connecting heterogeneous networks that is prone to disruptions in connectivity. MeDeHa is complementary to the IRTF’s Bundle Architecture: besides its ability to store messages for unavailable destinations, MeDeHa can bridge the connectivity gap between infrastructure-based and multi-hop infrastructure-less networks. It benefits from network heterogeneity (e.g., nodes supporting more than one network and nodes having diverse resources) to improve message delivery. For example, in IEEE 802.11 networks, participating nodes may use both infrastructure- and ad-hoc modes to deliver data to otherwise unavailable destinations. It also employs opportunistic routing to support nodes with episodic connectivity. One of MeDeHa’s key features is that any MeDeHa node can relay data to any destination and can act as a gateway to make two networks inter-operate or to connect to the backbone network. The network is able to store data destined to temporarily unavailable nodes till the time of their expiry. This time period depends upon current storage availability as well as quality-of-service needs (e.g., delivery delay bounds) imposed by the application. We showcase MeDeHa’s ability to operate in environments consisting of a diverse set of interconnected networks and evaluate its performance through extensive simulations using a variety of scenarios with realistic synthetic and real mobility traces. Our results show significant improvement in average delivery ratio and a significant decrease in average delivery delay in the face of episodic connectivity. We also demonstrate that MeDeHa supports different levels of quality-of-service through traffic differentiation and message prioritization.     

多无线电协作技术与异构网络融合

异构网络融合是未来网络技术发展的必然趋势。异构网络的融合面临着高延迟、高消耗、低速率等诸多方面的“瓶颈”。为克服这些“瓶颈”,满足异构网络融合的需求,多无线电协作技术应运而生。通过多无线电间的相互协作和对多无线电资源的有效管理及合理分配,能够有效地提高网络吞吐量,降低无线设备的能量消耗,减少异构网络间切换的延迟,从而为实现真正的异构网络无缝融合提供了可能。     

All-optical networks with sparse wavelength conversion

Unlike broadcast-and-select networks, wavelength-routing networks offer the advantages of wavelength reuse and scalability and are thus suitable for wide-area networks (WANs) We study the effects of topological connectivity and wavelength conversion in circuit-switched all-optical wavelength-routing networks. A blocking analysis of such networks is given. We first propose an analytical framework for accurate analysis of networks with arbitrary topology. We then introduce a model for networks with a variable number of converters and analyze the effect of wavelength converter density on the blocking probability. This framework is applied to three regular network topologies that have varying levels of connectivity: the ring, the mesh-torus, and the hypercube. The results show that either a relatively small number of converters is sufficient for a certain level of performance or that conversion does not offer a significant advantage. The benefits of conversion are largely dependent on the network load, the number of available wavelengths, and the connectivity of the network. Finally, the tradeoff between physical connectivity, wavelength conversion, and the number of available wavelengths is studied through networks with random topologies     

Broadband transport — the synchronous digital hierarchy

All data networks require a physical transmission medium to convey information between network nodes. Within a local environment this physical medium might, for example, take the form of an Ethernet LAN, but wide area connections are provided using telecommunications constant bit rate transmission equipment. Furthermore, the assumption that data networking is simply the provision of WAN connectivity for large corporate networks is becoming dated. The explosion of interest in the Internet means that, for transport networks, the term data may encompass voice, video and multimedia applications for delivery to both home and office. This places additional requirements on the network infrastructure as each service has specific transport requirements.Network operators are currently in the process of deploying core networks of equipment conforming to the ITU-T Recommendations for a synchronous digital hierarchy (SDH), but many networks also contain a significant proportion of older transmission technologies. This paper provides a review of transmission technology and describes the impact of such networks on the transport of data.     

Simplified Analysis of Coupled Transmission-Line Networks

A relatively simple method is presented for analyzing coupled transmission-line networks by using network graphs and graph transformations. The network graph symbolism is easy to draw and to manipulate. All the graphs consist only of inductor, capacitor, and transformer symbols, and straight lines, which represent unit elements. The method of analysis is illustrated by several two-wire-line and multiwire-line examples. Also presented are several new useful transmission-line transformations and a graph equivalent for the general coupled transmission-line network. The graph-transformation method has four principal advantages: 1) explicit open-wire-line equivalent circuits of coupled line networks can be obtained relatively easily and without knowledge of network synthesis techniques; 2) the form of equivalent circuits can often be obtained without using any algebra; 3) at each step of the analysis, a positive-real network in graph form is available; consequently, in many analysis problems several equivalent circuits for the same network are derived; and 4) multiport networks are as easily dealt with as two-port networks.     

A general framework for developing adaptive fault-tolerant routingalgorithms

It is shown that Cartesian product (CP) graph-based network methods provide a useful framework for the design of reliable parallel computer systems. Given component networks with prespecified connectivity, more complex networks with known connectivity and terminal reliability can be developed. CP networks provide systematic techniques for developing reliable fault-tolerant routing schemes, even for very complex topological structures. The authors establish the theoretical foundations that relate the connectivity of a CP network, the connectivity of the component networks, and the number of faulty components: present an adaptive generic algorithm that can perform successful point-to-point routing in the presence of faults: synthesize, using the theoretical results, this adaptive fault-tolerant algorithm from algorithms written for the component networks: prove the correctness of the algorithm: and show that the algorithm ensures following an optimal path, in the presence of many faults, with high probability     

Load balancing clustering and routing for IoT-enabled wireless sensor networks

Internet of things (IoT) devices are equipped with a number of interconnected sensor nodes that relies on ubiquitous connectivity between sensor devices to optimize information automation processes. Because of the extensive deployments in adverse areas and unsupervised nature of wireless sensor networks (WSNs), energy efficiency is a significant aim in these networks. Network survival time can be extended by optimizing its energy consumption. It has been a complex struggle for researchers to develop energy-efficient routing protocols in the field of WSNs. Energy consumption, path reliability and Quality of Service (QoS) in WSNs became important factors to be focused on enforcing an efficient routing strategy. A hybrid optimization technique presented in this paper is a combination of fuzzy c-means and Grey Wolf optimization (GWO) techniques for clustering. The proposed scheme was evaluated on different parameters such as total energy consumed, packet delivery ratio, packet drop rate, throughput, delay, remaining energy and total network lifetime. According to the results of the simulation, the proposed scheme improves energy efficiency and throughput by about 30% and packet delivery ratio and latency by about 10%, compared with existing protocols such as Chemical Reaction Approach based Cluster Formation (CHRA), Hybrid Optimal Based Cluster Formation (HOBCF), GWO-based clustering (GWO-C) and Cat Swarm Optimization based Energy-Efficient Reliable sectoring Scheme with prediction algorithms (P_CSO_EERSS). The study concludes that the protocol suitable for creating IoT monitoring system network lifetime is an important criteria.     

Connectivity analysis for dynamic movement of vehicular ad hoc networks

Speed variation is one of the main challenges in deriving the connectivity related predictions in mobile ad-hoc networks, especially in vehicular ad hoc networks (VANETs). In such a dynamic network, a piece of information can be rapidly propagated through dedicated short-range communication, or can be carried by vehicles when multihop connectivity is unavailable. This paper proposes a novel analytical model that carefully computes the connectivity distance for a single direction of a free-flow highway. The proposed model adopts a time-varying vehicular speed assumption and mathematically models the mobility of vehicles inside connectivity. According to the dynamic movability scenario, a novel and accurate closed form formula is proposed for probability density function of connectivity. Moreover, using vehicular spatial distribution, joint Poisson distribution of vehicles in a multilane highway and tail probability of the expected number of vehicles inside single lane in a multilane highway are mathematically investigated. The accuracy of analytical results is verified by simulation. The concluded results provide helpful insights towards designing new applications and improving performance of existing applications on VANETs.     

Shrinking network development time-scales: flexible virtualnetworks

A new type of virtual network is presented which allows the virtual network owner to exert control over their network resources in a completely flexible fashion. These virtual networks use a technique known as `switchlets', which result from partitioning the resources, both physical and logical, of a switch. Each partition is a switchlet. Switchlets from different physical switches may be interconnected together in a manner consistent with the physical connectivity of the real switches. Each set of interconnected switchlets can be controlled by its own system, called a `control architecture'. Such an arrangement results in a set of virtual networks, each with its own control architecture. These control architectures may be identical, that is they may be different instances of the same control architecture, or they may be radically different. This paper examines how switchlets can be used to provide functionality which is either impossible or problematic to provide using conventional approaches to network control     

On the connectivity in finite ad hoc networks

Connectivity and capacity analysis of ad hoc networks has usually focused on asymptotic results in the number of nodes in the network. In this letter we analyze finite ad hoc networks. With the standard assumption of uniform distribution of nodes in [0, z], z > 0, for a one-dimensional network, we obtain the exact formula for the probability that the network is connected. We then extend this result to find bounds for the connectivity in a two-dimensional network in [0, z]²     

Impact of Interference on the Wireless Ad-Hoc Networks Capacity and Topology

It is wide spread belief that wireless mobile ad-hoc networks will be a further evolutionary step towards ubiquitous communication and computing. Due to the mobility of the network nodes, the strongly varying radio propagation conditions and the varying data traffic load these networks constitute a very dynamic environment. One essential step in evaluating the true benefit of this new technology consists of estimates and constraints concerning the scalability and performance of such networks. Using a simple model we discuss analytically the effect of interference on the link quality and connectivity of large networks. It turns out that the outage probability rapidly increases with increasing traffic load. Furthermore, we investigate the connectivity of the network under varying traffic load and find a percolation phase transition at a particular value of the traffic load. We discuss the dependence of these effects on parameters characterizing the receiver and the radio propagation conditions.     

无线传感器网络自适应功率控制策略

无线传感器网络功率控制技术对于网络的拓扑连通、能量效率、网络容量、吞吐量、实时性等性能均有显著影响,是其实用化的重要支撑技术。该文提出了一种适用于无线传感器网络的自适应功率控制策略APCS(Adaptive Power Control Strategy),该策略是只需要局部信息的分布式算法,通过调整路径损耗指数和功率控制参数可以获得性能极佳的目标拓扑,并能满足实时性和容错能力要求较高的应用场景。另外,该算法还采用了动态功率调整以保持网络的连通性,延长网络的生命周期。仿真结果证实了所提方法的有效性。     

On the Relationship Between Transmission Rate and Network Capacity in Multi-Radio Multi-Channel Wireless Mesh Networks

This paper quantitatively investigates the relationship between physical transmission rate and network capacity in multi-radio multi-channel wireless mesh networks by using mixed-integer linear programming to formulate the joint channel assignment and routing problem. The numerical results show that the rate lower than the highest available one can improve the network capacity due to increased connectivity. It is also shown that the lower transmission rate is able to utilize abundant channels more effectively due to the higher degree of freedom in channel assignment. Finally, it is shown that joint rate, channel assignment and routing improves the network capacity further.     

Connectivity-Preserved and Force-Based Deployment Scheme for Mobile Sensor Network

This paper considers the self-deployment of wireless sensor networks. Conventional deployment problem usually focuses on enhancing the coverage, while the conditions for network connectivity are largely simplified. We present a deployment scheme to enhance the coverage while keeping the network connected at each step of the deployment. Our scheme contains two parts. The coverage improvement part proposes an improved force-based mechanism. A limit is provided to determine the sensors which should attractive each other, so the wasted overlap and communication resource can be reduced. The connectivity preservation part provides constrains for the movement distance of each sensor, in order to take account of both connectivity and coverage enhancement. Some simulation results are presented to show the connectivity preservation and coverage maximization properties of our mechanism.     

Optimal Transmit Power in Wireless Sensor Networks

Power conservation is one of the most important issues in wireless ad hoc and sensor networks, where nodes are likely to rely on limited battery power. Transmitting at unnecessarily high power not only reduces the lifetime of the nodes and the network, but also introduces excessive interference. It is in the network designer's best interest to have each node transmit at the lowest possible power while preserving network connectivity. In this paper, we investigate the optimal common transmit power, defined as the minimum transmit power used by all nodes necessary to guarantee network connectivity. This is desirable in sensor networks where nodes are relatively simple and it is difficult to modify the transmit power after deployment. The optimal transmit power derived in this paper is subject to the specific routing and medium access control (MAC) protocols considered; however, the approach can be extended to other routing and MAC protocols as well. In deriving the optimal transmit power, we distinguish ourselves from a conventional graph-theoretic approach by taking realistic physical layer characteristics into consideration. In fact, connectivity in this paper is defined in terms of a quality of service (QoS) constraint given by the maximum tolerable bit error rate (BER) at the end of a multihop route with an average number of hops.     

Security based on network topology against the wiretapping attack

In wireless networks, an attacker can tune a receiver and tap the communication between two nodes. Whether or not some meaningful information is obtained by tapping a wireless connection depends the security protocols used. One may use cryptographic techniques to secure the communications. In this article we discuss an alternate way of securing the communication between two nodes. We provide a simple security protocol against a wiretapping attack based on the network topology. Although we study the problem from a theoretical perspective, our protocol is easily implementable. Our protocol is at least as secure as any other protocol against these attacks. We show that an attacker can get any meaningful information only by wiretapping those links that are necessary for the communication between the sender and the receiver. We use techniques from network encoding. Our protocol works for any network topology, including cycle networks. We note here that acyclicity is the main assumption in much of the network encoding literature.