基于梯度的无线传感器网络能耗分析及能量空洞避免机制

在基于"梯度汇聚"模型的无线传感器网络 (Wireless sensor networks, WSNs)中, 因节点间能量消耗不平衡而引发的能量空洞一直是影响网络生存周期的重要原因. 本文分别分析了无通信干扰的自由空间环境和瑞利衰落环境下网络中节点的能量消耗,提出了一种基于节点能量非均匀分布的能量空洞避免机制,即根据节点的能耗水平为每个节点储备不同的初始能量.并结合通信干扰、休眠机制等因素,研究了基于"梯度汇聚"模型的无线传感器网络生存周期的上界和下界. 模拟结果表明,该机制提高了能量的利用效率,延长了网络的生存周期.     

感知距离参数优化的无线传感器网络节能的研究

无线传感器网络(WSNs)覆盖是WSNs的关键问题,它反映了网络对目标区域的探测能力,节点的感知距离的优化能够很好地解决WSNs区域覆盖要求的同时使得能量消耗最低.研究了基于节点感知距离参数调节的WSNs节能区域覆盖方案,建立了感知半径之和最小的数学模型,采用遗传算法求解该模型,得到一个最优解.仿真结果表明:与传统覆盖方案比较,所提方案在满足覆盖要求的同时有效地降低了网络能量消耗.     

基于网络编码的WSNs数据收集方法

无线传感器网络(WSNs)监测数据的收集方式方法是目前的研究热点,而无线传输的广播特性又使得网络编码非常适合于无线网络。在介绍网络编码原理、核心思想以及在WSNs应用现状的基础上,提出了一种基于部分网络编码的自适应WSNs数据收集方法,该方法针对簇网络拓扑结构,簇成员节点把网络编码数据发送给簇头节点,簇头节点利用随机网络编码的方式把数据传输到Sink节点。实验结果表明:该机制具有能耗较低和汇报数据较准确的特点。     

一种网络延迟精确控制的调度算法

在网络数据传输调度中，基于最早时限优先（EDF）的算法具有单点最优的延迟界限控制能力。现有的各种EDF改进算法，主要着眼于提供延迟上界的保证能力，而当采用机顶盒之类的缓冲能力较弱的设备作为客户终端时，还需要网络提供精确的延迟下界控制能力。在原有EDF改进算法的基础上提出了精确延迟界控制的最早时限优先算法。该算法不但能同时保证延迟上界和下界，还使得节点可以独立地决定为数据流分配的缓冲区大小，并增加了节点允许抖动量的取值范围，从而提高了节点数据的转发效率。     

无线传感器网络中的簇头节点能耗平衡策略

无线传感器网络（WSNs）具有集中式数据收集和多对一数据通信等特点,使得越靠近汇聚节点的簇头节点能耗越大,最终导致网络中心出现能量空洞。提出一种基于簇内节点分配的簇头节点能耗平衡策略,根据WSNs的分簇汇聚拓扑结构,分析了其中簇头节点的能量消耗情况;在此基础上,通过在各簇内分配一定数量的基本节点,并成比例地增加附加节点的方式,使网络中各簇头节点的能量消耗相等。仿真结果表明：该策略能够适应网络规模和负载的动态变化,最终达到平衡簇头节点能耗的目的。     

输电线路在线监测WSNs优化部署研究

应用于输电线路在线监测的无线传感器网络(WSNs)通常呈长链型,存在跳数多、时延大的问题。引入具备无线公网通信模块的异构节点能够优化WSNs时延性能。考虑网络中传感器节点分布不均匀引起的数据分布不均匀这一普遍现象及其对时延的影响,建立了异构WSNs的最大时延模型;同时考虑网段划分和异构节点部署对时延的影响,提出了一种基于局部搜索思想的网络优化部署方法来优化网络时延。仿真结果表明:上述方法能有效降低网络最大时延,提高网络实时性。     

一种休眠机制下无线传感器网络的自治愈方法

为减少无线传感器网络(WSNs)大规模应用中出现的节点同步失效、数据丢失的问题,通过对现有WSNs应用系统的研究,提出了一种全网节点同步休眠机制下WSNs的自治愈方法.详细介绍了该方法的设计思路、实现方法及测试过程.测试结果表明:此方法可针对数据丢失和时间同步失效的节点进行节点自救,实现丢失节点的再入网、再同步,提高WSNs系统的稳定性,为WSNs的应用提供更好的条件.     

无线传感器网络节点的低功耗设计

无线传感器网络(WSNs)能够协作地实时监测、感知和采集各种环境对象的信息,并将信息传递给系统用户主机进行分析处理。节点具有感知和路由的功能,在实际的应用中,功耗是影响节点工作寿命的关键因素。设计分析了WSNs系统功率消耗的构成,并从硬件和软件方面提出和总结了WSNs的低功耗设计方法,设计了一种低功耗的WSNs节点,并进行了测试,结果证明:该方法适合WSNs节点的应用,具有易使用、低功耗特点。     

基于电量检测的WSNs智能休眠方法

为使无线传感器网络（WSNs）中传感器节点的电池电量得到充分利用并降低传感节点能量消耗,提出了一种基于传感节点电量检测的WSNs智能休眠方法,以达到智能化管理WSNs传感节点电池电量的目的。详细地论述了WSNs智能休眠方法的设计思路和实现方法。测试结果表明：此休眠方法可＂智能＂地降低WSNs节点的功耗,为WSNs的进一步发展与应用奠定了一定的基础。     

一种基于分簇的无线传感器网络GPSR协议

在实际应用中,无线传感器网络(WSNs)中的节点分布不均匀且节点能量有限,由于节点工作量大小不同,导致节点能量损耗不均衡,从而影响WSNs生存周期.为了延长网络生存周期,提出一种基于分簇的WSNs GPSR协议.该协议首先将网络划分为若干个簇,每个簇需选择合适的簇头,而簇头选择以剩余能量为指标,并在簇内轮换.簇内采用改进的贪婪算法将数据汇集到簇头节点,有效避免了局部最小化问题.仿真实验表明:该协议能延长网络生存周期,提高数据传输成功率.     

Reliable networks with unreliable sensors

Wireless sensor networks (WSNs) deployed in hostile environments suffer from a high rate of node failure. We investigate the effect of such failure rate on network connectivity. We provide a formal analysis that establishes the relationship between node density, network size, failure probability, and network connectivity. We show that large networks can maintain connectivity despite a significantly high probability of node failure. We derive mathematical functions that provide lower bounds on network connectivity in WSNs. We compute these functions for some realistic values of node reliability, area covered by the network, and node density, to show that, for instance, networks with over a million nodes can maintain connectivity with a probability exceeding 95% despite node failure probability exceeding 53%.     

Detecting Sybil attacks in Wireless Sensor Networks using neighboring information

As the prevalence of Wireless Sensor Networks (WSNs) grows in the military and civil domains, the need for network security has become a critical concern. In a Sybil attack, the WSN is subverted by a malicious node which forges a large number of fake identities in order to disrupt the network’s protocols. In attempting to protect WSNs against such an attack, this paper develops a scheme in which the node identities are verified simply by analyzing the neighboring node information of each node. The analytical results confirm the efficacy of the approach given a sufficient node density within the network. The simulation results demonstrate that for a network in which each node has an average of 9 neighbors, the scheme detects 99% of the Sybil nodes with no more than a 4% false detection rate. The experiment result shows that the Sybil nodes can still be identified when the links are not symmetric.     

无线多跳网QoS性能统计性边界的研究

为保证无线多跳网的服务质量（QoS）,需要求解其性能边界。基于统计型流量包络建立了无线多跳网的数据流传输模型,在此模型的基础上利用统计网络演算理论推导了无线多跳网单节点的时延统计性边界、端到端的时延统计性边界以及端到端数据积压统计性边界。仿真实验结果表明,不同数据流的测量值都在数值计算的边界范围之内,表明基于统计网络演算理论的无线多跳网QoS边界模型具有较好的性能。     

A secure and robust temporal credential-based three-factor user authentication scheme for wireless sensor networks

User authentication is one of the most important security services required for the resource-constrained wireless sensor networks (WSNs). In user authentication, for critical applications of WSNs, a legitimate user is allowed to query and collect the real-time data at any time from a sensor node of the network as and when he/she demands for it. In order to get the real-time information from the nodes, the user needs to be first authenticated by the nodes as well as the gateway node (GWN) of WSN so that illegal access to nodes do not happen in the network. Recently, Jiang et al. proposed an efficient two-factor user authentication scheme with unlinkability property in WSNs Jiang (2014). In this paper, we analyze Jiang et al.’s scheme. Unfortunately, we point out that Jiang et al.’s scheme has still several drawbacks such as (1) it fails to protect privileged insider attack, (2) inefficient registration phase for the sensor nodes, (3) it fails to provide proper authentication in login and authentication phase, (4) it fails to update properly the new changed password of a user in the password update phase, (5) it lacks of supporting dynamic sensor node addition after initial deployment of nodes in the network, and (6) it lacks the formal security verification. In order to withstand these pitfalls found in Jiang et al.’s scheme, we aim to propose a three-factor user authentication scheme for WSNs. Our scheme preserves the original merits of Jiang et al.’s scheme. Our scheme is efficient as compared to Jiang et al.’s scheme and other schemes. Furthermore, our scheme provides better security features and higher security level than other schemes. In addition, we simulate our scheme for the formal security analysis using the widely-accepted AVISPA (Automated Validation of Internet Security Protocols and Applications) tool. The simulation results clearly demonstrate that our scheme is also secure.     

无线传感器网络中一种ARMA流量预测的拥塞控制算法

在无线传感器网络中,由于各节点的通信能力、计算能力、存储能力等都比较有限,使其需采取有别于传统网络的拥塞控制策略.本文针对传感网络特有的多对一、多跳通信方式经常导致网络拥塞的缺陷,提出一种基于流量预测的拥塞避免算法(SCATP).该算法通过ARMA模型分析流经各节点的当前流量,预测网络下一时刻的拥塞状况,并据此进行流量分配,从而实现拥塞控制的同时保证数据的可靠传输.仿真实验表明,SCATP算法在延迟、抖动率、吞吐量和能量有效性等方面能有效改善网络的服务质量.     

无线传感器网络中基于能量检测的定位研究

在许多无线传感器网络的应用中,节点定位是其关键技术之一,而定位精度的高低在很大程度上取决于距离测量的精度。针对射频信号受各种干扰影响而出现测距不精确的问题,该文对能量检测采用改进的限幅平均滤波方法,校正测量的节点间点到点的距离,并优选信标节点,最后用加权最小二乘法进行定位。实验及仿真结果表明,本定位算法可以提高测距精度...     

Energy-aware node placement,topology control and MAC scheduling for wireless sensor networks

In the WSNs, the nodes closer to the sink node have heavier traffic load for packet forwarding because they do not only collect data within their sensing range but also relay data for nodes further away. The unbalanced power consumption among sensor nodes may cause network partition. This paper proposes efficient node placement, topology control, and MAC scheduling protocols to prolong the sensor network lifetime, balance the power consumption of sensor nodes, and avoid collision. Firstly, a virtual tree topology is constructed based on Grid-based WSNs. Then two node-placement techniques, namely Distance-based and Density-based deployment schemes, are proposed to balance the power consumption of sensor nodes. Finally, a collision-free MAC scheduling protocol is proposed to prevent the packet transmissions from collision. In addition, extension of the proposed protocols are made from a Grid-based WSN to a randomly deployed WSN, enabling the developed energy-balanced schemes to be generally applied to randomly deployed WSNs. Simulation results reveal that the developed protocols can efficiently balance each sensor node’s power consumption and prolong the network lifetime in both Grid-based and randomly deployed WSNs.     

Nonlinear Filtering Under Stochastic Communication Protocol with Unknown Scheduling Probability

In this paper, the UKF-type nonlinear filtering problem is investigated for general nonlinear systems under stochastic communication protocols (SCPs) with unknown scheduling probabilities. In order to avoid the data collision and alleviate the network communication burden, SCPs, allowed only one sensor node to send data via the shared network, are exploited to orchestrate the scheduling order of sensor nodes. Different from traditional assumptions with accurate statistics, the scheduling probability of the selected node is unknown, but lies in a reliable interval with known upper and lower bounds. Due to the unknown probabilities, the exact estimation error covariance is not available and hence its upper bound is derived with the help of adding zero terms and eigenvalues of positive definite matrices. Such an upper bound is dependent on known upper and lower bounds of the scheduling probabilities and further utilized to reasonably design the filter gain at each time instant. In light of the obtained covariance and the filter gain, an improved unscented transformation is developed to carry out the designed UKF-type nonlinear filter by improving traditional approximate mean and covariance. Furthermore, the impact of the uncertain size of unknown scheduling probabilities is thoroughly discussed. Finally, a numerical example is given to confirm the effectiveness of the proposed nonlinear filter.

     

On the design of efficient ATM routing schemes

In this paper we deal with the problem of designing virtual path layouts in ATM networks when the hop-count is given and the load has to be minimized. We first prove a lower bound for networks with arbitrary topology and arbitrary set of connection requests. This result is then applied to derive lower bounds for the following settings: (i) one-to-all (one node has to be connected to all other nodes of the network) in arbitrary networks; (ii) all-to-all (each node has to be connected to all other nodes in the network) in several classes of networks, including planar and k-separable networks and networks of bounded genus. We finally study the all-to-all setting on two-dimensional meshes and we design a virtual path layout for this problem. When the hop-count and the network degree are bounded by constants, our results show that the upper bounds proposed in this paper for the one-to-all problem in arbitrary networks and for the all-to-all problem in two-dimensional mesh networks are asymptotically optimal. Moreover, the general lower bound shows that the algorithm proposed in Gerstel (Ph.D. Thesis, Technion-Haifa, Israel, 1995) for the all-to-all problem in k-separable networks is also asymptotically optimal. The upper bound for mesh networks also shows that the lower bound presented in this paper for the all-to-all problem in planar networks is asymptotically tight.     

路由深度对Sink轨迹固定传感器网络的影响

无线传感器网络中,使用移动Sink进行数据采集能够减少网络节点死亡速度,延长网络时间,是最有效均衡网络负载的方法之一。在实际应用中,移动Sink通常采用固定路径策略,同时路由深度的改变直接影响网络拓扑和路由选择结果。比较了在不同路由深度下,采用4种典型固定策略的移动Sink网络的网络能耗、网络寿命和包延时。仿真结果表明:在较小的路由深度下,外边界策略能更好地降低节点能耗,延长网络寿命;内边界策略能取得更好的覆盖和较低的时延。