分簇无线传感器网络中根校验全分集LDPC码设计与能效分析

高效的差错控制编码技术(ECC)可以增强无线传感器网络传输稳定性、网络的能量利用效率。为了充分利用无线传感器网络中蕴含的分集资源应对恶劣信道环境导致的高差错概率,该文研究了基于根校验全分集LDPC码的差错控制编码技术。首先,提出在分簇无线传感器网络中,基于根校验全分集LDPC码的编码方案;其次,设计了适用于所提方案的速率兼容全分集LDPC码字结构。最后,分析了所提编码系统的能效。仿真结果表明,在信道条件较差的环境中(仿真中,信道噪声大于410-4 mW),采用该文的编码方案,能够显著提高无线传感器网络的能效。     

虚拟多天线无线传感器网络

提出一种基于虚拟多天线技术的分布式和协作的无线传感器网络,分析了该虚拟多天线无线传感器网络的性能。同点到点的无线传感器网络相比较,在天线传输信号能量相同的情况下,虚拟多天线无线传感器网络的误比特概率(BER)更小;或者在同样误比特概率情况下,虚拟多天线无线传感器网络的天线传输信号能量更低。这些特性能够提高无线传感器网络的性能或延长无线传感器网络的使用寿命。     

协同通信在无线传感网中的应用

差错性能、吞吐量一直是无线通信追求的关键参数,协同通信可以在终端不安装多天线的基础上获得近似MI-MO(Multiple Input Multiple Output)技术的协同分集增益,提高系统性能或吞吐量。能效性是无线传感网中的关键参数,将协同通信应用在基于分簇的无线传感器网络(WSN)中,可以提高整个网络的能效性,以达到节省能量、延长整个网络寿命的目标。介绍了协同通信在无线传感器网络的结合应用方案,对这种结合的能效性能的最新研究给出了分析介绍,最后总结了研究的关键问题以及未来的发展趋势和研究方向。     

无线传感器网络中的整流天线技术研究进展

本文介绍了适用于无线传感器网络的、能进行无线输能的整流天线和能进行无线定位的时间反演算法.适用于无线传感器网络的整流天线要求紧凑的天线结构,高效的微波能量到直流电量的转换效率以及较高的入射波频率.利用时间反演算法的时-空聚焦特性,可解决无线传感器网络中节点无线定位问题,以提高整流天线的效率.     

基于MIMO的无线认知传感器网络研究

作为现代无线通信的核心技术,MIMO(多输入多输出)利用发射端和接收端的多副天线,来改善无线通信性能,而无需额外的无线带宽。MIMO中的空间分集、空间复用、波束形成、智能天线等可以帮助WCSN(无线认知传感器网络)接入有价值的频谱,提高链路质量和频谱效率。文章分析MIMO在阵列增益、分集增益和复用增益等方面的优势,介绍空时分组编码、空时网格编码和分层空时编码的工作原理,给出MIMO无线认知传感器网络的基本中继策略。     

一种在物理层实现协作分集的无线传感器网络

无线传感器网络通常具有存在大量冗余节点、共同的传送目标和能量资源极其有限等特性,因此可以在不同的协议层面上实现协作传输以提高能量有效性,从而延长网络的生命周期.本文研究了一种在物理层进行协作分集完成无线传感器网络中远距传输的方法,提出了可实现的信令和远程接收算法,分析了等效网络多径信道特性和远程接收机能够获得的最大分集增益以及影响分集增益的因素,提出了在分布式网络中提高空间分集增益的方法.     

一种用于WSN的微小型UWB雷达天线设计

超宽带雷达不受雨、雪、声、风等自然环境的干扰,可用于无线传感器网络并全天候工作;在通信领域,超宽带雷达可避免多径干扰问题,解决无线传感器网络在复杂多径环境中的应用局限问题。故超宽带雷达可以与无线传感器网络形成天然的结合。为满足无线传感器网络低功耗、体积小的要求,设计了一种微小型超宽带雷达天线。该天线为共面波导方式馈电的贴片式微带天线。仿真结果表明,天线具有体积小、带宽广(1.78~2.38 GHz)、全向性好的优点,满足无线传感器网络应用需求,并可避免与已用无线通信频段的干扰,具有广阔的应用前景。     

基于分布式中继选择的自适应协作传输方案

协作分集通过使网络用户共享彼此天线以形成虚拟多天线阵列,可以显著提高网络容量,然而针对网络拓扑的动态变化与无线传输的时变特性,仅靠协作分集并不能十分有效地解决这些问题,必须结合考虑相应的自适应传输策略.本文提出动态网络环境中协作中继的最佳选择准则,在此基础上给出最佳协作中继的分布式选择协议.根据协作中继与源节点间的无线信道质量,进一步提出一种自适应协作传输方案,以有效抵抗多用户网络环境中的无线衰落.此外,对自适应协作传输方案的误码性能,在瑞利衰落信道下进行相应的理论分析,得到了系统误比特率的解析表达式,据此给出数值仿真实验以进行性能比较.结果表明:相对于传统协作分集而言,本文提出的自适应协作传输方案获得了进一步的性能增益,误比特率显著下降.     

现代移动通信中发射分集技术研究

基于发送端多天线系统的发射分集技术是现代移动通信系统中抗信道衰落影响的一项关键技术。全面介绍发射分集技术的概念和实现方式,利用频率、时间、空间、极化、角度、调制等各种无线资源均可实现有效的发射分集方案,并且详细分析了各类典型的发射分集技术的特点和性能,理论分析有助于推广多天线发射分集系统在实际通信系统中的进一步应用。     

智能天线小型化策略之双极化天线

首先介绍智能天线小型化的必要性,然后利用电磁仿真软件的仿真结果分析城区环境下极化信道的特性以及极化天线带来的极化分集效果,最后讨论双极化智能天线的结构和应用双极化智能天线应关注的问题.     

Achieving maximum flow in interference-aware wireless sensor networks with smart antennas

Directional antenna offers various benefits for wireless sensor networks, such as increased spatial reuse ratio and reduced energy consumption. In this paper, we formulate the maximum flow problem as an optimization problem in interference-limited wireless sensor networks with switched beam directional antennas. The optimization problem is solvable in the presence of an omniscient controller, but it is NP-hard. Therefore, we seek a distributed algorithm to achieve the maximum flow through jointly routing and scheduling. The maximum flow between given source destination pair is determined forwardly hop by hop and is verified by the proposed feasible condition at downstream nodes. This method works for both single-beam antenna and multi-beam antenna with some variation in the feasibility condition.     

一款基于HFSS仿真的倒F蛇型印制天线

设计了一种用于2.4 GHz智能无线传感器的倒F蛇型天线,.使用HFSS仿真和设计,根据优化后的天线模型参数,最终设计集成在无线传感器印制电路板上印制天线,使天线可达到最佳的效果.该天线的仿真和实测结果表明,在2.45 GHz的中心工作频率下,回波损耗小于-12dB,带宽约为100 MHz,阻抗50.58+j0.55,满足了IEEE 802.15.4协议的要求.     

一种基于收集树协议的工业无线传感器网络动态路由机制

无线HART(Highway Addressable Remote Transducer)是当前工业无线传感器网络中应用最为广泛的协议,但无线HART没有提供动态路由机制以满足对工业无线网络应用至关重要的稳定性和鲁棒性。该文在无线HART协议基础上,提出一个基于收集树协议的可应用于工业无线传感器网络的动态路由机制。它占用时分多址(TDMA)超帧中的前几个时间片来产生和维护网络拓扑。通过仿真实验从3个方面对该动态路由机制进行了评估:拓扑生成时间,链路质量及网络拓扑的稳定性。仿真和评估结果表明该动态路由机制可以在基于TDMA的工业无线传感器网络中应用。     

一种LEACH路由协议算法的改进与分析

基于传统的LEACH协议,提出了一种改进协议LEACH-CND。对无线传感器网络的簇头选举进行了优化,主要依据节点的剩余能量选举簇头,并求出网络的最佳簇头数。其次,基于椭圆曲线密码体制的优势,针对无线传感器网络节点轻量级身份密钥加密算法进行了探讨。最后,在MATLAB环境下对优化后的协议进行了仿真,证明了其可行性。达到了延长网络生存时间的目的。     

Self-propagating mal-packets in wireless sensor networks: Dynamics and defense implications

Self-propagating mal-packets have become an emergent threat against information confidentiality, integrity, and service availability in wireless sensor networks. While playing an important role for people to interact with surrounding environment, wireless sensor networks suffer from growing security concerns posed by mal-packets because of sensor networks’ low physical security, lack of resilience and robustness of underlying operating systems, and the ever-increasing complexity of deployed applications.In this paper, we study the propagation of mal-packets in 802.15.4 based wireless sensor networks. Based on our proposed mal-packet self-propagation models, we use TOSSIM, a simulator for wireless sensor networks, to study their propagation dynamics. We also present a study of the feasibility of mal-packet defense in sensor networks. Specifically, we apply random graph theory and percolation theory to investigate the immunization of highly-connected nodes, i.e., nodes with high degrees of connectivity. Our goal is to partition the network into as many separate pieces as possible, thus preventing or slowing down the mal-packet propagation. We study the percolation thresholds of different network densities and the effectiveness of immunization in terms of connection ratio, remaining link ratio, and distribution of component sizes. We also present an analysis of the distribution of component sizes.     

一种无线传感器网络的能耗平衡覆盖模型

针对无线传感器网络节点能量有限、最小覆盖方法能耗不均衡的问题,该文提出了一种能耗平衡的连通覆盖模型,并对模型进行了分析与仿真。模型利用Voronoi划分和Delaunay三角剖分对传感器网络进行分割,判别重复覆盖目标区域的冗余传感器节点,采用节点到sink点的跳数对节点分层,进而提出选择休眠节点的方法。仿真结果表明,由模型建立的非最小连通覆盖集所导出的无线传感器网络,能够平衡节点能耗、使用优化路由、减弱路由关键点的影响。     

Minimum latency joint scheduling and routing in wireless sensor networks

Wireless sensor networks are expected to be used in a wide range of applications from environment monitoring to event detection. The key challenge is to provide energy efficient communication; however, latency remains an important concern for many applications that require fast response. In this paper, we address the important problem of minimizing average communication latency for the active flows while providing energy-efficiency in wireless sensor networks. As the flows in some wireless sensor network can be long-lived and predictable, it is possible to design schedules for sensor nodes so that nodes can wake up only when it is necessary and asleep during other times. Clearly, the routing layer decision is closely coupled to the wakeup/sleep schedule of the sensor nodes. We formulate a joint scheduling and routing problem with the objective of finding the schedules and routes for current active flows with minimum average latency. By constructing a novel delay graph, the problem can be solved optimally by employing the M node-disjoint paths algorithm under FDMA channel model. We further present extensions of the algorithm to handle dynamic traffic changes and topology changes in wireless sensor networks.     

Wireless smart sensor with small spiral antenna on Si-substrate

This paper presents a wireless smart sensor (WSS) with a thermoelectric sensor, a wireless transmitter and a small spiral antenna on a single package. To transmit a sensor signal, the wireless transmitter was designed to consist of an amplifier, a modulator, an oscillator, a buffer stage and an antenna. The wireless transmitter used dual pulse position modulation for low-power transmission. The fabricated transmitter has a sampling frequency of 2.6 kHz and an output carrier wave frequency of 300 MHz band due to the higher far field radiation of the transmitted signals from inside the body. The small size spiral antenna on the chip was fabricated for the transmission of carrier waves. The antenna has a bandwidth of 270-360 MHz for VSWR<2 and a gain of −40 dBi. The fabricated sensor, transmitter and spiral antenna were packaged with bond-wire on a single package. The WSS consumed a power of about 16.9 mW at the supply power of 5 V. The electric field strength of the WSS was measured to be 64.6 dB μV/m at a distance of 3 m. The wireless operation of the fabricated WSS was confirmed by demonstrating that the sensor signal was modulated by the transmitter and that the modulated sensor data was transmitted through the small size spiral antenna.     

无线传感器网络中移动目标跟踪算法研究

由于单个传感器节点的通信、处理和感知能力有限,所以传感器节点必须协同工作才能够完成任务。本文介绍了无线传感器网络的研究现状,阐述了目前成形的无线传感器网络协议与体系结构,阐述了针对面向目标跟踪的无线传感器网络涉及到的一些关键技术,并对现有的一些无线传感器网络中移动目标协同跟踪算法以及未来的发展方向进行了论述。