无线传感器网络中基于伸展树的感知节点分布优化

In a sensor network, reasonable distribution of sensor nodes will do much good to the improvement of sensorial ability. In a sensor network constructed by randomly scattering, a better sensing coverage can be achieved by topology adjustment utilizing mobility of some sensor nodes. To solve this problem, we define an extending-tree in the sensor network using Voronoi diagrams and Delaunay network. On this base, a new optimization algorithm of sensor node distribution based on genetic algorithm is designed, which provides a sound effective means to improve the sensorial ability of network. Simulation output shows that this algorithm can achieve an optimizing node distribution in the object area, by which sensorial ability of the whole sensor network can be improved at a relatively low cost.     

Improving the Reliability of Computer Communication Networks

For networks that are directed or can be represented by a directed network,reversing one or more of the uni-directional links may provide the ability to reconnect a network that has been disconnected by link failure.In this paper,a new approach to reconfigure such networks is proposed.We develop a linear time algorithm which,when reachability has been destroyed by the removal of a single link,optimally restores reachability through the reversal of selected links.Multi-link failure reconnectability is discussed and an algorithm with polynomial complexity is given which provides a nearly optimum solution to reconnect the network.We show that the reliability of a network that allows reversals is at least twice more than that in which reversals are not permitted.Unfortunately,the reconnection of some networks cannot be established.Therefore,we discuss the maximization of reachability of such networks so that each node can reach maximum number of the other nodes.     

New Distributed Positioning Algorithm Based on Centroid of Circular Belt for Wireless Sensor Networks

This paper presents a new distributed positioning algorithm for unknown nodes in a wireless sensor network.The algorithm is based exclusively on connectivity.First,assuming that the positions of the anchor nodes are already known,a circular belt containing an unknown node is obtained using information about the anchor nodes that are in radio range of the unknown node,based on the geometric relationships and communication constraints among the unknown node and the anchor nodes.Then,the centroid of the circular belt is taken to be the estimated position of the unknown node.Since the algorithm is very simple and since the only communication needed is between the anchor nodes and the unknown node,the communication and computational loads are very small.Furthermore,the algorithm is robust because neither the failure of old unknown nodes nor the addition of new unknown nodes influences the positioning of unknown nodes to be located.A theoretical analysis and simulation results show that the algorithm does not produce any cumulative error and is insensitive to range error,and that a change in the number of sensor nodes does not affect the communication or computational load.These features make this algorithm suitable for all sizes of low-power wireless sensor networks.     

Detecting and Locating Failures in Communication Networks

The connectivity of a strongly connected network may be destroyed after link damage.Since many networks are connected by directed links,the reachability may be restore by altering the direction of one or more of the links and thus reconfiguring the network.The location of the failed link ust first be determined.In this paper,we examine new methods to determine the location of failed links and nodes in networks.A routing test approach is proposed and the conditions under which communication networks may be tested are discussed Finally,an adaptive algorithm and a heuristic algorithm that can locate a single failed link or a single failed node are presented.     

Cross-layer Enhancement to Multi-hop Routing in Sensor Networks： an Empirical Study

Lossy link is one of the unique characteristics in random-deployed sensor networks. We envision that robustness and reliability of routing cannot be ensured purely in network layer. Our idea is to enhance the performance of routing protocol by cross-layer interaction. We modified mint protocol, a routing protocol in TinyOS and proposed an enhanced version of mint called PA-mint. A transmission power control interface is added to network layer in PA-mint. When routing performance of the current network is not satisfied, PA-mint monotonically increases the transmission power via the interface we added. PA-mint is able to connect orphan nodes and robust to node mobility or key nodes failure. In the case that automatic request retransmission is employed, the number of retransmissions can be reduced by PA-mint. Results from experiments show that PA-mint increases the reliability and robustness of routing protocol by cross-layer interaction.     

An efficient algorithm for mobile localization in sensor networks

Node localization is a fundamental problem in wireless sensor network.There are many existing algorithms to estimate the locations of the nodes.However,most of the methods did not consider the presence of obstacles.In practice,obstacles will lead to blockage and reflection of communication signals between sensor nodes.Therefore,the presence of obstacles will greatly affect the localization result.In this paper,we implement an obstacle-handling algorithm based on the localization tool developed by MIT,The experimental result shows that the enhanced algorithm can reduce the average distance error by up to 46%,compared to the original algorithm.     

NBgossip: An Energy-Efficient Gossip Algorithm for Wireless Sensor Networks

Gossip-based algorithms for information dissemination have recently received significant attention for sensor and ad hoc network applications because of their simplicity and robustness.However,a common drawback of many gossip- based protocols is the waste of energy in passing redundant information over the network.Thus gossip algorithms need to be re-engineered in order to become applicable to energy constrained networks.In this paper,we consider a scenario where each node in the network holds a piece of information(message)at the beginning,and the objective is to simultaneously disseminate all information(messages)among all nodes quickly and cheaply.To provide a practical solution to this problem for ad hoc and sensor networks,NBgossip algorithm is proposed,which is based on network coding and neighborhood gossip. In NBgossip,nodes do not simply forward messages they receive,instead,the linear combinations of the messages are sent out.In addition,every node exchanges messages with its neighboring nodes only.Mathematical proof and simulation studies show that the proposed NBgossip terminates in the optimal O(n)-order rounds and outperforms the existing gossip-based approaches in terms of energy consumption incurred in spreading all the information.     

Optimal bandwidth utilization of all-optical ring with a converter of degree 4

In many models of all-optical routing,a set of communication paths in a network is given,and a wavelength is to be assigned to each path so that paths sharing an edge receive different wavelengths .The goal is to assign as few wavelengths as possible,in order to use the optical bandwidth efficiently.If a node of a network contains a wavelength converter,any path that passes through this node may change its wavelength .Having converters at some of the nodes can reduce the mumber of wavelengths required for routing,This paper presents a wavelength converter with degree 4and gives a routing algorithm which shows that any routing with load L can be realized with L wavelengths when a node of an all-optical ring hosts such a wavelength converter.It is also proved that 4 is the minimum degree of the converter to reach the full utilization of the available wavelengths if only one mode of an all-optical ring hosts a converter.     

SR-MAC: A Low Latency MAC Protocol for Multi-Packet Transmissions in Wireless Sensor Networks

Event detection is one of the major applications of wireless sensor networks (WSNs). Most of existing medium access control (MAC) protocols are mainly optimized for the situation under which an event only generates one packet on a single sensor node. When an event generates multiple packets on a single node, the performance of these MAC protocols degrades rapidly. In this paper, we present a new synchronous duty-cycle MAC protocol called SR-MAC for the event detection applications in which multiple packets are generated on a single node. SR-MAC introduces a new scheduling mechanism that reserves few time slots during the SLEEP period for the nodes to transmit multiple packets. By this approach, SR-MAC can schedule multiple packets generated by an event on a single node to be forwarded over multiple hops in one operational cycle without collision. We use event delivery latency (EDL) and event delivery ratio (EDR) to measure the event detection capability of the SR-MAC protocol. Through detailed ns-2 simulation, the results show that SR-MAC can achieve lower EDL, higher EDR and higher network throughput with guaranteed energy efficiency compared with R-MAC, DW-MAC and PR-MAC.     

An energy-driven unequal clustering protocol for heterogeneous wireless sensor networks

Due to the limitation of energy resources, energy efficiency is a key issue in wireless sensor networks (WSNs). Clustering is proved to be an important way to realize hierarchical topology control, which can improve the scalability and prolong the lifetime of wireless sensor networks. In this paper, an energy-driven unequal clustering protocol (EDUC) for heterogeneous wireless sensor networks is proposed. EDUC includes an unequal clustering algorithm and an energy-driven adaptive cluster head rotation method. The unequal size of clusters can balance the energy consumption among clusters, and the energy-driven cluster head rotation method can achieve the balance of energy consumption among nodes within a cluster, which reduces the waste of energy. Simulation experiments show that EDUC balances the energy consumption well among the cluster heads and prolongs the network lifetime.     

无线传感器网络中节点非均匀分布的能量空洞问题

节点非均匀分布策略能缓解无线传感器网络中的能量空洞问题.文中从理论上探讨这种策略,证明在节点非均匀分布的圆形网络中,如果节点持续向Sink节点发送数据,能量空洞现象将无法避免,而当节点数目满足一定关系时,网络中能够实现次优能耗均衡.文中提出一种节点非均匀分布策略及相应的路由算法用于实现这种次优能耗均衡.模拟结果显示网络生存周期终止时,处于网络内部的节点几乎达到了能耗均衡.     

一种无线传感器网络目标的最优覆盖算法

无线传感器网络点状目标覆盖的算法中,集合分割算法虽简单,但效率低且仅适用于每个传感器节点能量都相等的网络模型.为此,我们对集合分割算法进行改进,提出一种启发式贪心最优覆盖算法.该算法适用于节点能量正态分布的网络模型,采用了关键目标优先覆盖策略和节点能效最大化策略,延长了网络覆盖生命期,提高了算法的效率.实验表明新算法网络生命期延长80%以上,有更好的适应性和稳定性.     

无线传感器网络的任意覆盖率节点配置

研究了任意覆盖率下的无线传感器网络分布式节点自动配置问题. 首先, 针对正六边形拓扑架构下的网络覆盖, 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, 从而得到了理想条件下部分覆盖的最优节点配置. 考虑到实际系统中有限的节点密度和节点的随机分布, 进一步提出了一种可以在此条件下实现任意覆盖率的部分覆盖协同优化算法(Optimized collaborative partial coverage, OCPC). OCPC通过节点间的动态协同唤醒最接近于理想配置的工作节点并使其他节点睡眠以节省能量. 以尽可能少的工作节点达到网络的覆盖和连通需求并降低网络的能耗, 进而达到网络的感知任务和能量消耗的有效折衷. 仿真表明, OCPC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连通, 同时, 与经典覆盖算法PEAS (Probing environment and adaptive sleeping)和OGDC (Optimal geographic density control)相比, 在网络的节能方面也具有明显的优越性.     

基于蜂窝结构的传感器网络覆盖问题求解算法

在无线传感器网络中,求解能够完全覆盖目标区域的最小覆盖集是个NP难问题.在传感器节点数目较多时,目前只能通过近似算法求解.蜂窝结构是覆盖二维平面的最佳拓扑结构,但不能直接用于求解无线传感器网络的覆盖问题.提出了一种基于蜂窝结构的覆盖问题求解算法,在该算法迭代求解过程的每一阶段,选出一个节点加入到初始为空的节点集合中,并使得该节点集合的拓扑结构接近于蜂窝结构,直至该节点集合成为覆盖集.该算法在最坏情况下的时间复杂度为O(n3),这里n为传感器节点总数.实验结果表明该算法可在很短的时间内执行完,在所得覆盖集的大小方面要优于现有的覆盖问题求解算法.     

基于RSSI的无线传感器网络圆环质心定位算法

针对无线传感器网络质心算法受节点分布均匀程度的影响, 少数锚节点增大定位误差, 提出了一种圆环质心算法. 该算法以未知节点为圆心, 将未知节点通信区域划分成半径由大到小的圆环, 通过圆环剔除容易增大定位误差的锚节点, 筛选出合适的锚节点, 并在圆环上寻找近似等边三角形来进一步减小定位误差. 同时提出了利用RSSI值来形成圆环的方法. 仿真结果表明, 在100m×100m的区域中, 随机投放100个节点, 通信半径为20m, 锚节点数为20时, 圆环质心算法与质心算法相比, 定位精度提高了11%.     

基于无线传感器网络的红海湾监测预警系统节点布署

针对汕尾红海湾开发利用价值,设计切实可行的无线传感器网络预警监测系统,重点在对监测的海域设计无线传感器节点部署策略,网络中分别部署功能强大和较为节能的两种传感器节点,并在功能强大的节点间引用虚拟力算法达到最优部署,该算法具有较强的全局寻优能力。仿真实验表明该部署有效地提高了网络覆盖率,优化了网络性能。     

基于低成本超声传感器的无线传感网生存环境地图构建研究

移动传感器网络节点在监测环境过程中,采集到大量有误差的环境地图数据,导致构建的传感器网络生存环境地图质量低、实时性差.针对以上问题,提出了一种适用于低成本、轻数据量、多网络节点的基于超声传感器组的环境地图构建算法.首先对超声波测量数据进行高斯滤波处理,其次利用处理后的数据进行单一网络节点所属区域地图的构建,再次提取单一节点地图的点特征,并进行匹配,进而得到融合后的全局地图,最终实现传感器网络节点生存环境地图的构建.进一步通过优化子图拼接顺序,降低了构图数据与实际环境数据的误差,提高了传感器网络节点生存环境的地图质量.     

基于节点优先权和兴趣数据筛选的传感器网络分簇算法

无线传感器节点工作时仅由自身携带的电池供电,因此高效控制节点能耗可以延长整个网络生命周期,提高网络整体利用率。针对环境监测类场景,提出了一种基于节点优先权和兴趣数据筛选的分簇算法,该算法同时考虑了节点分布距离和剩余能量,将这两个属性换算成簇头选举的优先权权值。此外,在簇头确定后簇头通过相应的数据筛选方法对每一轮子节点发来的数据进行处理,有选择地将数据传到基站。仿真结果表明,该算法在能量控制方面有较好的表现,明显地延长了网络生命周期。     

基于新量子遗传算法的无线传感器网络感知节点的分布优化

无线传感器网络中,感知节点的合理分布对于提高网络的感知能力和收集信息能力都具有重要作用。对于随机分布方式产生的感知网络,可以利用节点的移动性对特定感知节点的位置进行调整从而改善网络整体的感知覆盖范围。为此,针对无线传感器网络感知节点的分布优化问题进行了研究,给出了无线传感器网络覆盖控制模型,并提出了一种基于新量子遗传算法的分布优化机制。仿真结果表明新量子遗传算法在优化性能上优于传统遗传算法,能够有效提高网络整体的感知能力。