基于室内传播模型的无线传感器网络节点部署策略研究

为保证在室内部署无线传感器网络节点时实现感知面积完全覆盖特定区域,在2．4GHz的ISM频段,依据对数距离模型,分析了因天线高度不同引起的节点有效覆盖面积的变化问题,讨论了有效通信半径与有效感知半径的关系。在传统的平面节点部署方法的基础上,提出了一种考虑天线高度等环境因素的室内无线传感器网络节点快速部署方案,定义了部署规则和补充规则,从而避免了因天线高度变化而引起的感知黑洞的产生。仿真和试验结果表明该方案可以有效保证规定区域的完全覆盖,具有应用价值。     

Controlled deployments for wireless sensor networks

In wireless sensor networks (WSNs), the operation of sensor nodes has to rely on a limited supply of energy (such as batteries). To support long lifetime operation of WSNs, an energy-efficient way of sensor deployment and operation of the WSNs is necessary. A new controlled layer deployment (CLD) protocol to guarantee coverage and energy efficiency for a sensor network is proposed. CLD outperforms previous similar protocols in that it can achieve the same performances and guarantee full area coverage and connection using a smaller number of sensors. It can also ameliorate the 'cascading problem' that reduces the whole network lifetime. Finally, analysis and simulation results show that CLD can use fewer sensor nodes for coverage and also increases the lifetime of the sensor network when compared with the probing environment and adapting sleeping (PEAS) protocol.     

Power optimised channel coding in wireless sensor networks using low-density parity-check codes

Energy consumption of low-density parity-check (LDPC) codes in different implementations is evaluated. Decoder's complexity is reduced by finite precision representation of messages, that is, quantised LDPC decoder, and replacement of function blocks with look-up tables. It is shown that the decoder's energy consumption increases exponentially with the number of quantisation bits. For the sake of low-power consumption, 3-bit magnitude and 1-sign bit representation for messages are used in the decoder. It is concluded that high-rate Gallager codes are as energy efficient as the Reed-Solomon codes, which till now have been the first choice for wireless sensor networks (WSNs). Finally, it is shown that using LDPC codes in WSNs can be justified even more by applying the idea of trading the transmitter power with the decoder energy consumption. By exploiting the trade-off inherent in iterative decoding, the network lifetime is increased up to four times with the 3-6 regular LDPC code. Hence, it is inferred that the LDPC codes are more efficient than the block and the convolutional codes.     

Integrated channel assignment and data aggregation routing problem in wireless sensor networks

In wireless sensor networks, data aggregation routing could reduce the number of data transmission so as to achieve efficient total energy consumption. However, this kind of data aggregation introduces data retransmission that is caused by co-channel interference from neighbouring sensor nodes. Hence, more data aggregation leads to more extra energy consumption and significant retransmission delay from retransmission. This could jeopardise the benefits of data aggregation. One possible solution to circumvent retransmission caused by co-channel interference is to assign different channel to every sensor node that is within each other's interference range on the data aggregation tree. As the number of non-overlapping channels is limited in wireless networks, it is unlikely that we could assign a different channel to every sensor node on the data aggregation tree. Then, an interesting problem is to perform data aggregation routing in conjunction with channel assignment to minimise total transmission power under limited number of non-overlapping channels. This problem is an NP-complete problem. We devise heuristic algorithm, Iterative Channel Adjustment Data Aggregation Routing algorithm (ICADAR), and other three heuristics, to tackle this problem. From the simulation results, the ICADAR algorithm outperforms the other three algorithms under all experimental cases.     

无线传感器网络定位求精方法

为了提高传感器节点定位精度,将多种节点坐标计算方案(如极大似然估计、基于泰勒展开的最小二乘法和加权最小二乘法等)应用于定位求精中,并分析和比较了它们的性能.为了解决实际定位过程中锚节点存在的自身位置偏差,设计了相应的坐标求精方法,如总体最小二乘法和约束总体最小二乘法,在此基础上针对无线传感器网络定位误差的特点推广了定位误差的估计下限(参数无偏估计的Cramer-Rao下限).仿真实验结果给出了不同求精方案各自的求精性能和适用场合.在锚节点无位置误差的情况下,在泰勒展开基础上形成的加权最小二乘法更有利于精度提高;在锚节点有位置误差的情况下,约束总体最小二乘法对提高定位精度更有效.     

应用于无线传感网的接收信号强度指示器的设计

采用SMIC 0.18μm CMOS工艺设计了应用于无线传感网(WSN)的接收信号强度指示器(RSSI),其核心电路是采用跨导放大器构成的限幅器、半波整流器和相应的偏置电路。其工作在电流模形式下,对工艺角和温度具有良好的补偿特性。芯片测试结果表明:在电源电压为1.8V时,RSSI的直流功耗为4.14mW,2MHz输入信号频率下的检测范围为-58～-7dBm(以50Ω阻抗作参考),对应的输出指示直流电压为0.48～1.45V,检测斜率约为18.2mV/dB,非线性误差小于±0.7dB。芯片面积为0.654mm×0.430mm。     

无线传感器网络的流量自适应分簇算法协议

在分析LEACH路由协议算法的缺点的基础上,提出了一种用于无线传感器网络的基于流量自适应的TDMA分簇算法协议.该协议根据当前节点数据流量的变化,自适应地调整该节点在其簇内通信的时隙长度,减少节点空闲时消耗的能量和节点从睡眠到活跃状态来回切换的能量.仿真实验结果表明,与LEACH协议簇内时隙分配算法相比,运用这种新的时隙分配算法,可以节省节点的能量,提高网络的生存时间,改善网络性能.     

Voronoi-based relay placement scheme for wireless sensor networks

Energy consumption is a crucially important issue in battery-driven wireless sensor networks (WSNs). In most sensor networks, the sensors near the data collector (i.e. the sink) become drained more quickly than those elsewhere in the network since they are required to relay all of the data collected in the network to the sink. Therefore more balanced data paths to the sink should be established in order to extend the lifetime of the sensor network. Accordingly, a novel relay deployment scheme for WSNs based on the Voronoi diagram is proposed. The proposed scheme is applicable to both two-dimensional and three-dimensional network topologies and establishes effective routing paths that balance the traffic load within the sensor network and alleviate the burden on the sensors around the sink. Simulation results indicate that the number of relays deployed in the proposed scheme is similar to that deployed in the predetermined location scheme and is significantly less than that deployed in the minimum set cover scheme. Furthermore, the lifetime of the sensor network containing relay nodes deployed using the current scheme is longer than that achieved using either the predetermined location scheme or the minimum set cover scheme.     

Locating ineffective sensor nodes in wireless sensor networks

Ineffective sensor node (InESN) in a wireless sensor network (WSN) is defined as one whose position cannot be estimated by traditional localisation methods. Incremental localisation method is investigated and the existence of the InESNs is confirmed. By analysing the existing characteristics, the InESNs are classified into three categories: InESNs connecting with one known node, InESNs connecting with two known nodes and InESNs standing alone. It is impossible to locate the InESNs of the third category because they cannot receive any information from the known nodes. With a moving target in the WSN, a constrained least-squares formulation is developed to estimate the InESNs of the first two categories. Numerical evaluations are carried out to examine the performance of the proposed method and show that it is indeed effective for locating the InESNs. By incorporating the InESNs in the tracking applications, the performance of the target tracking can be greatly enhanced.     

MAC-layer channel utilisation enhancements for wireless mesh networks

The authors focus on a wireless mesh network, that is, an ad hoc IEEE 802.11-based network whose nodes are either user devices or Access Points providing access to the mesh network or to the Internet. By relying on some work done within the IEEE 802.11s TG, the network nodes can use one control channel and one or more data channels, each on separate frequencies. Then, some problems related to channel access are identified and a MAC scheme is proposed that specifically addresses the problem of hidden terminals and the problem of coexisting control and data traffic on different frequency channels. An analytical model of the MAC scheme is presented and validated by using the Omnet++ simulator. Through the developed model, we show that our solution achieves very good performance both in regular and in very fragmented mesh topologies, and it significantly outperforms the standard 802.11 solution.     

Distributed inference in wireless sensor networks

Statistical inference is a mature research area, but distributed inference problems that arise in the context of modern wireless sensor networks (WSNs) have new and unique features that have revitalized research in this area in recent years. The goal of this paper is to introduce the readers to these novel features and to summarize recent research developments in this area. In particular, results on distributed detection, parameter estimation and tracking in WSNs will be discussed, with a special emphasis on solutions to these inference problems that take into account the communication network connecting the sensors and the resource constraints at the sensors.     

Signal compression in wireless sensor networks

Signal compression is an important tool for reducing communication costs and increasing the lifetime of wireless sensor network deployments. In this paper, we overview and classify an array of proposed compression methods, with an emphasis on illustrating the differences between the various approaches.     

一种传感器网络的非均匀节能分簇模型

针对无线传感器网络中节点能耗不平衡导致系统生存时间缩短的问题,提出了一种无线传感器网络的非均匀节能分簇(UEEC)模型.UEEC通过自组织的方式和对簇头的动态选择,在靠近sink点(基站)的地方形成较小的簇,在远离sink点的地方形成较大的簇,从而使簇头能够对信息收集能耗与信息转发能耗进行平衡.同时,簇头的动态选举又能够把能耗平均分散在各个节点上.仿真结果表明,UEEC在减少与平衡无线传感器网络的节点能耗上有较好的性能,从而能够延长无线传感器网络的生存时间.     

一种新的分布式无线传感器网络定位方法

针对无线传感器网络节点能源受限的特征,以系统最小硬件开销为设计原则,提出了一种适用于基于测距的分布式定位方法(3/2-NANDB),该方法可在不增加单个独立节点硬件开销的情况下,利用附加的外部控制系统发射一个旋转定向波束充分挖掘节点间的冗余信息,有效排除节点位置的模糊性,从而可完全确定只有两个邻居节点的节点位置和部分只有一个邻居节点的节点位置,达到减少GPS携带节点数量、最大化网络内部可定位节点数目、扩大网络观察范围和延长无线传感器网络存活时间等目的.而利用该方法的节点二义性排除算法,还可以辅助其他现有的基于三邻居(3-NA)的定位算法提高整体定位性能.     

Operating systems and network protocols for wireless sensor networks

Sensor network protocols exist to satisfy the communication needs of diverse applications, including data collection, event detection, target tracking and control. Network protocols to enable these services are constrained by the extreme resource scarcity of sensor nodes-including energy, computing, communications and storage-which must be carefully managed and multiplexed by the operating system. These challenges have led to new protocols and operating systems that are efficient in their energy consumption, careful in their computational needs and miserly in their memory footprints, all while discovering neighbours, forming networks, delivering data and correcting failures.     

Game-theoretic medium access control protocol for wireless sensor networks

In the traditional medium access control (MAC) protocols for wireless sensor networks (WSNs), energy consumption is traded for throughput and delay. However, in future WSNs, throughput and delay performance had better not be sacrificed for energy conservation. Here first, an incompletely cooperative game-theoretic heuristic-based constraint optimisation framework is introduced to achieve the goals of throughput, delay and energy conservation simultaneously. Then a simplified game-theoretic MAC (G-MAC) protocol is presented, which can be easily implemented in WSNs. Simulation results show that compared with two typical MAC protocols for WSNs, sensor MAC and timeout MAC, G-MAC can increase system throughput, and decrease delay and packet-loss-rate, while maintaining relatively low energy consumption.     

面向传感网可信检测的协同感知策略

为了提高基于传感器网络的目标检测的检测精度和尽可能延长网络的寿命,将满足用户对检测精度要求的检测定义为可信检测,并提出了一种面向可信检测的协同感知策略。该策略首先对传感器的相关性及感知能力差异性进行定量分析,发现它们与传感器簇的感知性能的关联性,为实现传感器的协同选择提供依据;然后用一种分布式传感器协同选择方法进行传感器协同选择:根据传感器相关性、感知能力差异性及剩余能量来计算节点的重要性,之后按节点重要性选择合适的传感器。试验表明,与传统方法相比,该策略既能更好地满足用户对检测精度的要求,又能在实现能量均衡、延长网络寿命上取得更好的效果。     

无线传感网3D-MCM封装结构的设计与实现

设计和实现了一种新型的三维多芯片组件(3D-MCM).采用融合了FCOB(flip-chip on board)、COB(chip on board)、BGA(ball grid array)等技术的三维封装(3D packaging)形式,通过倒装焊和引线键合等互连技术在高密度多层有机基板上实现了塑封BGA器件和裸芯片的混载集成.对器件结构的散热特性进行了数值模拟,并对热可靠性进行了评估.实现了电功能和热机械可靠性,达到设计要求并付诸应用.     

一种低计算复杂度的无线传感器网络分簇定位算法

针对已有的集中式定位算法定位精度低,而分布式定位算法计算复杂度高、通信量大的问题,提出了一种适用于无线传感器网络的计算复杂度低的节点分簇定位算法.首先,提出满足最大连通度的多边界节点分簇算法,采用此算法把网络划分为若干个簇,各簇分别进行簇内节点定位;其次,各簇进行融合,最终实现全网节点的定位.仿真结果表明,这种分簇定位算法比分布式定位算法计算复杂度低、通信量小、定位精度相当或略差,比集中式定位算法计算复杂度低、通信量小、定位精度高.采用该算法可以降低传感器网络节点定位过程中的能耗,提高计算效率,延长网络寿命.     

支持性能测量的无线传感器网络实验床技术研究

针对目前无线传感器网络实验床普遍缺乏性能测量机制的问题,基于TinyOS的特点,提出了一种支持对实验对象进行现场测量的实验床体系结构.将轻量级测量实体嵌入到实验床中,对被测系统、测量指标进行约束与定义,设计了高能效的测量方法和测量算法,实现了对实验中节点能耗、链路质量、吞吐量、丢包率、时延、网络拓扑等性能参数的高效可靠获取,解决了传感器网络协议或应用的实时测试问题.该实验床技术支持分布式多点测量和平面、分簇、Multi-Sink等多种网络结构,提高了实验床设施的利用率和实验效率.实验案例证明了其良好的易用性、普适性和可扩展性.