面向车载容迟网络的连通性建模与仿真研究

针对车载容迟网络连通性建模进行了研究。首先假设车辆驶入道路的过程服从泊松分布,以及车辆在道路上的行驶速度服从正态分布。继而对基于泊松过程的车间时距分布进行推导,并以此导出行驶车辆在道路上的连通概率。为了验证所提假设和连通模型的正确性和有效性,以欧洲城市卢森堡在7:30 a.m.~8:30 a.m.时间段内的交通数据为实验场景,在城市交通仿真平台（simulation of urban mobility,SUMO）对车辆速度的概率分布、车辆到达率、道路中的平均车辆数及网络连通概率进行了理论计算和仿真实验分析。实验结果表明理论模型的计算值和仿真结果是一致的,所提出的假设和连通模型具有合理性和正确性。     

Bounds on maximum delay in networks with deflection routing

We consider the problem of finding the worst case packet transit delay in networks using deflection routing. Several classes of networks are studied, including many topologies for which deflection routing has been proposed or implemented (e.g., hypercube, Manhattan Street Network, shuffle-exchange network). We derive new upper bounds on the evacuation time of batch admissions, and present simple proofs for several existing bounds. Also derived are bounds on worst case transit delay for certain networks admitting packets continuously. To demonstrate the practical utility of our results, we compare a new delay bound to the maximum delay observed in simulations. The results have application in both protocol design and the determination of the required capacity of packet resequencing buffers     

Strong Menger connectivity with conditional faults on the class of hypercube-like networks

In this paper, we study the Menger property on a class of hypercube-like networks. We show that in all n-dimensional hypercube-like networks with n−2 vertices removed, every pair of unremoved vertices u and v are connected by min{deg(u),deg(v)} vertex-disjoint paths, where deg(u) and deg(v) are the remaining degree of vertices u and v, respectively. Furthermore, under the restricted condition that each vertex has at least two fault-free adjacent vertices, all hypercube-like networks still have the strong Menger property, even if there are up to 2n−5 vertex faults.     

具有时延性质的复杂网络牵制控制

该文主要是利用牵制控制方法对一类具有时延性质的复杂网络进行同步控制。该方法不同于最早的全局控制,仅是对网络中的部分节点进行控制。将这些节点的输出量的差值作为控制器从而达到等同于全局控制的效果。同时根据最新的网络结构可控原理计算出牵制控制所需要的最少节点数目,继而通过设定合适的Lyapunov函数,并基于稳定性和线性矩阵不等式等理论得出满足要求的控制器设计准则。最后,采用小世界模型进行仿真,进一步验证了结论的正确性。     

Novel results on stability analysis of neutral-type neural networks with additive time-varying delay components and leakage delay

The objective of this paper is to analyze the stability analysis of neutral-type neural networks with additive time-varying delay and leakage delay. By constructing a suitable augmented Lyapunov-Krasovskii functional with triple and four integral terms, some new stability criteria are established in terms of linear matrix inequalities, which is easily solved by various convex optimization techniques. More information of the lower and upper delay bounds of time-varying delays are used to derive the stability criteria, which can lead less conservative results. The obtained conditions are expressed with linear matrix inequalities (LMIs) whose feasible can be checked easily by MATLAB LMI control toolbox. Finally, two numerical examples are given to demonstrate the effectiveness of the proposed method.

     

具有时滞的脉冲随机神经网络的有限时间稳定性

本文研究具有时滞的脉冲随机神经网络的有限时间稳定性问题.利用Lyapunov泛函技术,线性矩阵不等式(LMIs)工具和平均脉冲区间条件,对反镇定型、中立型和镇定型3种类型的脉冲系统分别给出了基于矩阵不等式的有限时间均方稳定的充分条件,最后通过一个数值例子验证了理论结果的有效性.     

无线传感器网络连通性研究

为优化无线传感器网络的配置参数,减少网络拓扑结构变化次数,需对其组网算法和连通性问题进行研究。从概率论角度出发研究了网络参数之间的关系,在分析了节点连通度概率分布模型后,推导出了节点通信半径、节点个数、监测区域、连通度之间的关系,并在此基础上给出了一种连通性好且节能的无线传感器网络组网算法。通过仿真实验对算法进行验证,实验结果表明使用该方法组建的无线传感器网络连通性好,有很好的应用前景。     

A survey on coverage and connectivity issues in wireless sensor networks

A wireless sensor network (WSN) is composed of a group of small power-constrained nodes with functions of sensing and communication, which can be scattered over a vast region for the purpose of detecting or monitoring some special events. The first challenge encountered in WSNs is how to cover a monitoring region perfectly. Coverage and connectivity are two of the most fundamental issues in WSNs, which have a great impact on the performance of WSNs. Optimized deployment strategy, sleep scheduling mechanism, and coverage radius cannot only reduce cost, but also extend the network lifetime. In this paper, we classify the coverage problem from different angles, describe the evaluation metrics of coverage control algorithms, analyze the relationship between coverage and connectivity, compare typical simulation tools, and discuss research challenges and existing problems in this area.     

Invariant and attracting sets of Hopfield neural networks with delay

This paper studies invariant and attracting sets of Hopfield neural networks system with delay. Sufficient criteria are given for the invariant and attracting sets. In particular, we provide an estimate of the existence range of attractors by using invariant and attracting sets. Moreover, when the system has an equilibrium point, we obtain the sufficient conditions of global asymptotic stability of the equilibrium point. Several examples are also worked out to demonstrate the advantages of our results.     

Impact of bounded delay on throughput in multi-hop networks

This paper presents a closed form solution relating to the impact of bounded delays on throughput in multi-hop networks. In contrast to contemporary literature that largely focuses on average delay to estimate the Quality of Service, our model focuses on an upper bound of delay, referred to as delay threshold in this paper. Traffic that exceeds the delay threshold is treated as lost throughput. The results obtained can be used in scaling resources in a multi-hop network for attaining specified levels of throughput under different thresholds of acceptable delays. Both single-hop and multi-hop transfers are addressed. The theoretical analysis presented in this paper is further corroborated by simulation. The findings presented in this paper will be very relevant to multi-hop network applications where received data that are older than a specified threshold period are not relevant and must be discarded.     

Synchronization in networks of excitatory and inhibitory neurons with sparse,random connectivity

In model networks of E-cells and I-cells (excitatory and inhibitory neurons, respectively), synchronous rhythmic spiking often comes about from the interplay between the two cell groups: the E-cells synchronize the I-cells and vice versa. Under ideal conditions-homogeneity in relevant network parameters and all-to-all connectivity, for instance-this mechanism can yield perfect synchronization. We find that approximate, imperfect synchronization is possible even with very sparse, random connectivity. The crucial quantity is the expected number of inputs per cell. As long as it is large enough (more precisely, as long as the variance of the total number of synaptic inputs per cell is small enough), tight synchronization is possible. The desynchronizing effect of random connectivity can be reduced by strengthening the E --> I synapses. More surprising, it cannot be reduced by strengthening the I --> E synapses. However, the decay time constant of inhibition plays an important role. Faster decay yields tighter synchrony. In particular, in models in which the inhibitory synapses are assumed to be instantaneous, the effects of sparse, random connectivity cannot be seen.     

Analysis of power saving and its impact on web traffic in cellular networks with continuous connectivity

In this work, we analyze the power saving and its impact on web traffic performance when customers adopt the continuous connectivity paradigm. To this end, we provide a model for packet transmission and cost. We model each mobile user’s traffic with a realistic web traffic profile, and study the aggregate behavior of the users attached to a base station by means of a processor-shared queueing system. In particular, we evaluate user access delay, download time and expected economy of energy in the cell. Our study shows that dramatic energy saving can be achieved by mobile devices and base stations, e.g., as much as 70%–90% of the energy cost in cells with realistic traffic load and the considered parameter settings.     

无线传感器网络部分覆盖算法及连通性研究

研究了无线传感器网络在部分覆盖下的节点配置及网络连通性问题。首先,基于最优正六边形拓扑架构,给出了节点密集分布条件下的覆盖率与相邻工作节点间距的解析关系,并在已有的最优完全覆盖算法OGDC的基础上进行了扩展和改进,从而得到了一种新的网络节点配置算法EGDC（Extended OGDC Algorithm）。该算法可以有效地选择出合适的工作节点以达到任意给定覆盖率下的部分覆盖。此外,还给出了一种检验和评价网络连通性的方法,通过该方法可以对网络的连通性进行量化分析,并给出了一项评价网络连通性的指标。仿真表明,EGDC可以有效地实现任意期望覆盖率下的网络配置并保持网络的连通。     

混合突触作用下耦合时滞对模块神经元网络簇同步的影响

针对电突触耦合和化学突触耦合混合作用下含有耦合时滞的模块神经元网络,利用非线性动力学理论和数值仿真方法,探讨了耦合强度及耦合时滞对模块神经元网络簇同步特性的影响.结果发现,模块神经元网络中子网络内、子网络间的耦合强度都能促使簇放电神经元取得簇同步,但是时滞却对耦合诱导的簇同步具有显著的抑制作用.进一步的研究证实了本文所得的研究结果不依赖于子网络的数目与子网络的节点个数.需要指出的是,耦合时滞对神经元网络簇同步的抑制作用对治疗簇同步引发的一些神经性疾病(如帕金森病、癫痫等)具有一定的理论指导意义.     

Boundedness,hierarchy of fairness,and communication networks with delay

In this paper, we consider networks of communicating finite-state machines (CFSMs) with a delay-related fairness (T-fairness) constant imposed on all computations. The notion of T-fairness, in a sense, allows us to measure the degree of synchronization of parallel systems “quantitatively”. Based on the value of T, we define a hierarchy of unbounded networks. We are able to show that, in general, the hierarchy is infinite. However, if we restrict ourselves to networks of 2 machines, the hierarchy collapses all the way to the second level. We also derive the complexity result of the boundedness problem for CFSM networks with respect to T-fairness.     

感知无线电网络中的呼叫延迟阻塞概率研究*

呼叫允许控制是无线资源管理中的重要组成部分,是一种减少网络拥塞、保证服务质量和提高网络资源利用率的重要机制。在给定系统资源情况下,准确估计用户呼叫延迟阻塞概率,能为网络优化建设提供一个重要依据。在排队论——生灭过程的基础上,探讨了感知无线电（CR）网络中的呼叫延迟阻塞概率与系统资源的关系,并给出了估计公式,仿真结果表明其精确度很高。     

异质性和时滞作用下神经元网络的共振动力学

利用参数互异的Fitzhugh-Nagumo神经元构建了含耦合时滞的无标度神经元网络模型,通过数值模拟的方法,提出研究参数异质性和耦合时滞影响下神经元网络的共振动力学.结果发现,当耦合项中不含时滞时,适中的参数异质性能够使得神经元网络对外界弱周期信号的响应达到最优,即适中的参数异质性能够诱导神经元网络的共振响应,而且异质性诱导共振对耦合强度具有鲁棒性.更重要的是,耦合时滞对参数异质性作用下神经元网络的共振特性也有着显著性影响.当时滞约为信号周期的整数倍时,神经元网络能够周期性地出现共振现象,即适当的耦合时滞能够诱导神经元网络的多重共振,而且这种现象在异质性参数的适当范围内都能明显出现.     

具有不对称结构的广义时滞神经网络的动态分析

研究一类具有不对称互连结构的广义时滞神经网络的动态行为．通过构造适当的Lyapunov泛函及扇区条件，给出了平衡点渐近稳定的充分条件，并对由推论给出的一种小增益条件进行了分析．仿真结果进一步证明了结论的有效性．     

Fast symbolic computation of the worst-case delay in tandem networks and applications

Computing deterministic performance guarantees is a defining issue for systems with hard real-time constraints, like reactive embedded systems. In this paper, we use burst-rate constrained arrivals and rate-latency servers to deduce tight worst-case delay bounds in tandem networks under arbitrary multiplexing. We present a constructive method for computing the exact worst-case delay, which we prove to be a linear function of the burstiness and latencies; our bounds are hence symbolic in these parameters. Our algorithm runs in quadratic time in the number of servers. We also present an application of our algorithm to the case of stochastic arrivals and server capacities. For a generalization of the exponentially bounded burstiness (EBB) model, we deduce a polynomial-time algorithm for stochastic delay bounds that strictly improve the state-of-the-art separated flow analysis (SFA) type bounds.     

Modeling the influence of network delay on the user experience in distributed home-automation networks

Today’s modern home-automation systems and services (HASS) frequently communicate over public telecommunications networks, such as the Internet. Unfortunately, these communication networks do not usually provide sufficient quality (i.e., a predictable delay), which is generally assured in fieldbus HASS networks. Consequently, the user-perceived quality of experience (QoE) cannot be maintained at a satisfactory level when using different HASS devices communicating over an IP-based network. The data transferred over the Internet can experience a non-negligible delay that can have a considerable influence on the QoE. For this reason, the main goal of our research was to measure the influence of the network delay on a subjective QoE assessment, while interacting with some frequently used HASS tasks. The results show that users are satisfied if the delay is kept below 0.8?s, and that they can tolerate delays of over 2?s (depending on the level of the HASS task interactivity). Since such a user-perceived subjective QoE assessment is both time-consuming and expensive we also propose objective QoE assessment models to represent the influence of network delay on a subjective QoE assessment for various HASS tasks.