一种基于邻域信息的多信道自适应建网算法

为实现多信道无线自组网的高效建网,针对节点难以感知全网拓扑、其他所有节点的可用频谱以及无法获得同步信息的实际场景,提出了一种基于邻域信息的多信道自适应建网算法。该算法首先设计基于邻域信息的建网策略,使节点能够以自身信息为基础,充分利用可用信道情况、邻居簇首情况等有限的邻域信息进行自适应决策,以建立分簇结构的网络;然后提出基于最大熵原理的信道质量评价算法和基于多头绒泡菌模型的邻居簇首评价算法,分别对节点的可用信道和邻居簇首进行排序,指导节点在建网过程中选择合理的信道和簇首。仿真结果表明,所提建网算法能够使节点在实际场景通信受限的条件下以较小的通信开销完成建网,建立的网络在公共信道数量和簇规模方面也取得了较好的均衡。      

基于成对广播同步协议在WSNs耗能的研究

成对广播同步(PBS)是无线传感器网络同步研究的重要协议。它建立在仅接收端(ROS)同步基础上实现范围广阔的网络同步,并且能够在无线传感器网络节点的能耗方向有着不可忽视的作用。通过对单簇网络同步的研究,提出多簇网络同步并对多簇网络同步在无线传感器网络同步中全网成对选择算法(NPA)和基于组的成对选择算法(GPA)作出研究。最后对广播同步技术在应用中所出现的问题,提出了在此算法上新的研究方向。     

一种基于分簇的WSN时间同步算法

论文提出了一种基于分簇结构的无线传感器网络时间同步算法.在分簇网络结构中,参考DMTS,仿照TPSN采用在MAC层给控制帧标记时同戳的方式,实现了传感器节点的能量效率,进一步提高了时间同步精度.分析表明.本算法在精度和能耗上都有所改进.     

基于安全性的无线传感器网络时钟同步算法研究

无线传感器网络存储能力不高,导致以往提出的无线传感器网络时钟同步算法的安全性能不高、同步误差较大,现提出基于安全性的无线传感器网络时钟同步算法。基于安全性的无线传感器网络时钟同步系统中的父节点构建无线传感器网络和子节点,子节点通过与父节点进行数据交互,平衡无线传感器网络时钟同步,CC2530芯片将父节点和子节点进行连接。无线传感器网络时钟同步的运算工作在仿真器中完成,传输接口将父节点和子节点的交互信息输出到仿真器,为运算工作提供数据仿真源。安全性调试接口对父节点构建网络结果和时钟同步运算结果进行实时展示。系统对同步安全算法和同步算法语言的设计,较为有效地实现了无线传感器网络时钟同步。经实验验证可知,所提算法同步误差小,安全性能高。     

无线传感器网络能量有效时间同步算法研究

针对无线传感器网络中随着节点数目增多,传统的参考广播同步算法网络开销非常大的问题,该文提出一种能量有效的参考广播同步算法。该算法首先只对不相邻的两个接收节点在多个参考广播消息的条件下求平均相位偏差,并且对计算得出的相位偏差进行最大后验估计;其次采用最小二乘线性回归方法周期性地拟合时钟偏移,完成同步过程。仿真结果表明,能量有效的参考广播同步算法在同步精度方面有所改进的同时,有效减少了无线传感器网络的能量消耗。     

基于扩散机制的无线传感器网络时间同步协议

针对当前无线传感器网络时间同步协议普遍存在抗毁能力不足的缺陷,提出了一种基于扩散机制的无线传感器网络时间同步协议,全局时间通过邻居节点间定时随机交换时戳信息维护,取消同步发起节点在同步网络中可能带来的不安全隐患,实现同步网络拓扑最优.同时利用容错、时分等策略进一步提高同步网络的抗毁性能.通过对典型无线传感器节点的实际测试表明,该协议在抗毁能力、同步精度、可扩展能力等方面均取得了较好结果.     

基于移动参考节点的无线传感器时钟同步方法

现有对无线传感器网络节点中的时钟同步方法往往通过固定参考节点传递同步信息完成同步。对于固定参考节点通信范围外的节点,需要同步信息在节点间的多跳传输,这造成时间误差的累积以及节点多跳传输的能量损耗,从而影响同步的精度和网络能耗。为解决此问题,提出了基于移动参考节点和最优移动路径的时钟同步方法。首先,采用正六边形的蜂窝覆盖技术选取最优的时钟同步点。其次,结合最优覆盖和选址问题的数学模型,设计最短移动距离的路径。最后,提出了基于MAC层标记多个时间戳实现低能耗单跳同步的机制。与现有方法的实验对比表明,该方法提高了同步时间精度,并降低了通信能耗。     

基于多层抽样反馈的传感器网络时间同步算法

针对目前传感器网络时间同步算法存在的问题,提出了一种全网时间同步算法FTS(full-scale time synchronization),其基本思想是从整体角度对传感器网络实施逐轮次的推送式的时间同步操作,并通过少量抽样节点的反馈数据计算时间同步操作的有关参数.在常见的TelosB节点上给出了FTS算法的实现.实验和分析表明,FTS算法是一类收敛快速、资源高效、同步精度较高和运算复杂度较低的时间同步方法,目前已经在无线传感器网络测试平台上得到了应用.     

基于ZigBee节点的按需时间同步算法

简要阐述近年来无线传感网络时间同步（TPSN）算法的发展概况和影响无线传感器网络时间同步的因素,结合无线传感网络中路由节点与终端节点的特点,提出一种融合了参考广播同步（RBS）与TPSN算法设计,在保持同步精确度前提下,整个网络的功耗大大降低。通过实验采集到的数据分析了协议的可行性,证明该算法较适合于对节点密度高,终端节点较多的无线网络中,如工业有害气体的检测。     

一种高效的无线传感器网络MAC层方案

媒体接入控制协议(MAC)是影响无线传感器网络能量效率的重要方面,SMAC是其中具有代表性的方案。SMAC无法实现调度表的全网同步,只能形成多个在局部范围内同步的簇,簇间边界节点相对于内部节点能量消耗要快。针对这一问题提出了一种改进的MAC方案,利用调度表的全网同步来实现簇的合并,消除了边界节点,提高了MAC层的能量效率,使网络连通性得到提高。仿真证明了方案的有效性和可扩展性。本方案同时满足无线传感器网络分布式和经济性的要求。     

分簇型无线传感器网络时间同步机制的研究

提出了一种基于分簇型网络结构的时间同步算法。算法的主要思想是通过在簇建立阶段利用LEACH优化算法优化网络拓扑结构,降低网络的跳数,从而降低了时间同步精度由于跳数增加而导致的误差积累,为时间同步算法提供一个良好的网络结构。在LEACH优化算法中,簇首选取机制融入簇首节点的剩余能量和密度因子,并且提出了助理簇首节点用以均衡簇首节点的能量消耗。同时在时间同步阶段,采用双向时间同步机制和单向广播时间机制。实验仿真证明,提出的时间同步算法降低了网路的跳数,提高了时间同步精度,降低了节点的能量消耗,提高了网路的运行时间,具有一定的实用价值。     

移动水声异步网络自定位和时间同步联合的单向动态预测算法

节点位置的实时变化以及水下长传输时延等特性影响了移动水声异步网络(MUAANs)的时间同步与自定位精度。针对上述问题,该文研究并提出一种自定位和时间同步联合的单向动态预测算法。该算法通过建立时间同步与自定位联合的状态与观测模型,同时预测不同时刻下移动节点的位置信息与时钟差异,实现网络的联合位置跟踪与动态时间同步。与此同时,由于该算法仅采用节点间的单向信息传输即可实现自定位与时间同步,有效解决了由水下长传输时延导致的移动节点间双向信息交互时延差异的问题,提高了网络的自定位与时间同步精度和效率。仿真结果表明,该文所提算法可以高精度地联合预测移动水声异步网络的自定位与时间同步结果,且有效增强了网络的时间同步与自定位时间效率。     

DDBNF：一个分布式的动态蓝牙网络形成算法

提出了一个分布式的、支持节点移动性的蓝牙匹克网构造算法DDBNF,它可以有效地将随机分布在某个区域内的n个节点划分为若干个匹克网.该算法只需获得每个节点的本地拓扑信息(一跳邻居节点),基于权值大小选举主节点,允许每个普通从节点直接访问至少一个主节点,保证了每个节点对之间快速的匹克网间以及匹克网内通信.     

无线传感器网络中数据汇聚方案的研究

针对分簇网络拓扑结构中簇头节点能量消耗过快,综合考虑了节点的密集程度和剩余能量,采用节点自适应的簇头选择算法,选择部署越集中和剩余能量越大的节点作为簇头节点。同时节点引入了新鲜性信息熵模型,通过比较前后两次接收到的数据的差别程度,设置一个参考阈值来判断是否转发数据。这种数据汇聚算法有效地降低了数据的冗余,减少了能量消耗,增加了带宽利用率,延长了网络的生存期。     

Distributed Synchronization for OFDMA‐Based Wireless Mesh Networks

In this paper, we propose a distributed synchronization algorithm for wireless mesh networks based on orthogonal frequency division multiple access. For time and frequency synchronization, a node requests its neighbor nodes for a change of fast Fourier transform starting points, transmission times, and carrier frequencies needed for synchronization. The node also updates its own time and frequency elements through simple formulas based on request messages received from neighbor nodes using a guard interval and a cyclic prefix. This process with the cooperation of neighbor nodes leads to a gradual synchronization of all nodes in the network. Through a performance comparison with a conventional scheme, we obtain simulation results indicating that the proposed scheme outperforms the conventional scheme in random topologies and a grid topology.     

Some improved and generalized estimation schemes for clock synchronization of listening nodes in wireless sensor networks

A sender-receiver paradigm, in which a master and slave node exchange timing packets to estimate the clock offsets of the slave node and other nodes located in the common broadcast region of master and slave nodes, is adopted herein for synchronizing the clocks of individual nodes in a wireless sensor network (WSN). The maximum likelihood estimate of the clock offset of the listening node hearing the broadcasts from both the master and slave nodes was derived in [1] assuming symmetric exponential link delays. This paper advances those results in two directions. First, some improved estimators, each being optimal in its own class, are derived for the clock offset of the listening node and mean link delays. Second, the results are generalized by addressing the more realistic problem of clock offset estimation under asymmetric exponential delays. The results presented in this paper are important for time synchronization of WSNs, where these techniques can be utilized to achieve accurate clock estimates with reduced power consumption.     

Drift estimation using pairwise slope with minimum variance in wireless sensor networks

Time synchronization is mandatory for applications and services in wireless sensor networks which demand common notion of time. If synchronization to stable time sources such as Coordinated Universal Time (UTC) is required, employing the method of flooding in order to provide time synchronization becomes crucial. In flooding based time synchronization protocols, current time information of a reference node is periodically flooded into the network. Sensor nodes collect the time information of the reference node and perform least-squares regression in order to estimate the reference time. However, least-squares regression exhibits a poor performance since sensor nodes far away from the reference node collect the time information with large deviations. Due to this fact, the slopes of their least-squares line exhibit large errors and instabilities. As a consequence, the reference time estimates of these nodes also exhibit large errors.This paper proposes a new slope estimation strategy for linear regression to be used by flooding based time synchronization protocols. The proposed method, namely Pairwise Slope With Minimum Variance (PSMV), calculates the slope of the estimated regression line by considering the pairwise slope between the earliest and the most recently collected data points. The PSMV slope is less affected by the large errors on the received data, i.e. it is more stable, and it is more computationally efficient when compared to the slope of the least-squares line. We incorporated PSMV into two flooding based time synchronization protocols, namely Flooding Time Synchronization Protocol (FTSP) and PulseSync. Experimental results collected from a testbed setup including 20 sensor nodes show that PSMV strategy improves the performance of FTSP by a factor of 4 and preserves the performance of PulseSync in terms of synchronization error with 40% less CPU overhead for linear regression. Our simulations show that these results also hold for networks with larger diameters and densities.     

实现自组网互同步的一种单源同步法

针对自组网的特点,提出一种单源互同步算法,使各节点动态地选择与本节点直接通信的节点中主时钟频率最大的节点作为帧同步的同步源,并向其锁钟,进而实现全网的帧同步与时钟同步.经测试验证,该算法在抗摧毁性能、同步收敛速度、时钟同步准确性和稳定性等方面具有较为突出的优势.     

传感器网络中基于树的感知器分布优化

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信息收集能力以及提高网络的生存期限都具有重要的作用。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,利用 Voronoi 图以及相关 Delaunay 三角网定义了传感器网络中以sink 节点为中心的伸展树,并提出了基于遗传算法的感知节点分布优化算法。仿真结果表明,算法能够以较小代价对传感器网络进行节点的分布优化,从而有效提高网络整体的感知能力。     

Generating a fault-tolerant global clock using high-speed controlsignals for the MetaNet architecture

Describes a new technique, based on exchanging control signals between neighboring nodes, for constructing a stable and fault-tolerant global clock in a distributed system with an arbitrary topology. It is shown that it is possible to construct a global clock reference with a time step that is much smaller than the propagation delay over the network's links. The synchronization algorithm ensures that the global clock “tick” has a stable periodicity, and therefore, it is possible to tolerate failures of links and clocks that operate faster and/or slower than nominally specified, as well as hard failures. The approach taken is to generate a global clock from the ensemble of the local transmission clocks and not to directly synchronize these high-speed clocks. The steady-state algorithm, which generates the global clock, is executed in hardware by the network interface of each node. At the network interface, it is possible to measure accurately the propagation delay between neighboring nodes with a small error or uncertainty and thereby to achieve global synchronization that is proportional to these error measurements. It is shown that the local clock drift (or rate uncertainty) has only a secondary effect on the maximum global clock rate. The synchronization algorithm can tolerate any physical failure. It will continue to operate correctly on any connected segment of the network, i.e., it can tolerate any number of link and node failures, as long as the network remains connected