无线传感器网络中一种基于定向天线的节点定位算法

节点定位问题是无线传感器网络中的一个基本而非常重要的问题。已有的定位算法大致可以分为两类:基于测距的和无需测距的。基于测距的定位算法需要额外硬件的支持,成本较高,不适用于大规模的传感器网络;无需测距的定位算法不需要额外硬件的支持,是解决传感器网络节点定位问题的一个较为经济适用的方法。本文提出了一种新的基于定向天线的无需测距的分布式定位算法。其主要原理在于利用定向天线确定邻居节点之间的相对位置,然后判断未知节点是否在锚节点构成的三角形内。仿真研究表明,提出的算法是有效的,能够取得较好的定位精度。     

一种新的无线传感器网络DV-Hop算法

无线传感器网络[1]能够实时监测和采集网络分布区域内的各种检测对象信息,有着广泛的应用前景。节点自身定位是无线传感器网络的基础性问题之一。节点定位算法大致可分为两类:基于测距的算法和无需测距的算法。基于测距的算法对硬件的要求较高,无需测距的对硬件的要求不高。针对这种情况,为了提高算法精度,文中介绍了一种名叫RDV-hop算法的新的节点定位算法,这种算法结合RSSI与DV-hop两种算法的优点来进行节点定位。与老的DV-hop算法相比,这种新的算法极大的提高了定位的精确度。     

LIS: Localization based on an intelligent distributed fuzzy system applied to a WSN

The localization of the sensor nodes is a fundamental problem in wireless sensor networks. There are a lot of different kinds of solutions in the literature. Some of them use external devices like GPS, while others use special hardware or implicit parameters in wireless communications.In applications like wildlife localization in a natural environment, where the power available and the weight are big restrictions, the use of hungry energy devices like GPS or hardware that add extra weight like mobile directional antenna is not a good solution.Due to these reasons it would be better to use the localization’s implicit characteristics in communications, such as connectivity, number of hops or RSSI. The measurement related to these parameters are currently integrated in most radio devices. These measurement techniques are based on the beacons’ transmissions between the devices.In the current study, a novel tracking distributed method, called LIS, for localization of the sensor nodes using moving devices in a network of static nodes, which have no additional hardware requirements is proposed.The position is obtained with the combination of two algorithms; one based on a local node using a fuzzy system to obtain a partial solution and the other based on a centralized method which merges all the partial solutions. The centralized algorithm is based on the calculation of the centroid of the partial solutions.Advantages of using fuzzy system versus the classical Centroid Localization (CL) algorithm without fuzzy preprocessing are compared with an ad hoc simulator made for testing localization algorithms.With this simulator, it is demonstrated that the proposed method obtains less localization errors and better accuracy than the centroid algorithm.     

Cross-layer optimization using two-level dual decomposition in multi-flow ad-hoc networks

Localization is one of the most important issues in wireless sensor networks and designing accurate localization algorithms is a common challenge in recent researches. Among all localization algorithms, DV-Hop attracts more attention due to its simplicity; so, we use it as a basis for our localization algorithm in order to improve accuracy. The various evolutionary algorithms such as Genetic, Shuffled Frog Leaping and Particle Swarm Optimization are employed in different phases of the main DV-Hop localization algorithm. Simulation results prove that our proposed method decreases the localization error efficiently without additional hardware.     

Heterogeneous Cooperative Localization for Social Networks

Location-aware techniques has become a hot research topic with great value in commercial and military applications. Cooperative localization, which utilizes multiple sensors in portable devices to estimate locations of the mobile users in the social networks, is one of the most promising solution for the indoor geo-location. Traditional cooperative localization methods are based on ranging techniques, they are highly dependent on the distance interpreted from the received signal strength (RSS) or time of arrival from anchors. However, a precise ranging procedure demands high performance hardware which would increase the cost to the current mobile platform. In this paper, we describes four ranging-free probabilistic cooperative localization algorithms: centroid scheme, nearest neighbor scheme, kernel scheme and AP density scheme to improve the accuracy for the indoor geo-location using current mobile devices. Since the GPS sensor embedded in the smart phone is able to provide accurate location information in the outdoor area, those mobile nodes can be used as calibrated anchors. The position of the indoor mobile node can be estimated by exchanging locations and RSSs from shared wireless access points information between the target node and anchor nodes. An empirical evaluation of the system is given to demonstrate the feasibility of these cooperative localization algorithms by reporting the results in a real-world environments, e.g. suburban area and city downtown. Moreover, we compared our results with the WiFi positioning system made by Skyhook Wireless to validate the accuracy of the proposed algorithms. Meanwhile, a Monte Carlo simulation is carried out to evaluate the performance of the cooperative algorithms under different scenarios. Results show that given the same scenario setting, the AP density scheme and kernel scheme outperform than other schemes.     

Sensor Localization under Limited Measurement Capabilities

In this article we survey the latest progress on sensor localization, focusing on distance measurement techniques and localization algorithms for a sensor to determine its own location. We illustrate why inaccurate distance measurements, arising from tight hardware design constraints, raise challenges in sensor localization and how proposed approaches strive to overcome these challenges. We conclude that sensor localization algorithms must be designed to accommodate different application requirements in terms of costs, energy consumption, and localization accuracy     

Novel DV-Hop localization algorithm for wireless sensor networks

Many improved DV-Hop localization algorithm have been proposed to enhance the localization accuracy of DV-Hop algorithm for wireless sensor networks. These proposed improvements of DV-Hop also have some drawbacks in terms of time and energy consumption. In this paper, we propose Novel DV-Hop localization algorithm that provides efficient localization with lesser communication cost without requiring additional hardware. The proposed algorithm completely eliminates communication from one of the steps by calculating hop-size at unknown nodes. It significantly reduces time and energy consumption, which is an important improvement over DV-Hop—based algorithms. The algorithm also uses improvement term to refine the hop-size of anchor nodes. Furthermore, unconstrained optimization is used to achieve better localization accuracy by minimizing the error terms (ranging error) in the estimated distance between anchor node and unknown node. Log-normal shadowing path loss model is used to simulate the algorithms in a more realistic environment. Simulation results show that the performance of our proposed algorithm is better when compared with DV-Hop algorithm and improved DV-Hop—based algorithms in all considered scenarios.     

红外图像处理算法硬件实现验证系统

由红外探测器采集得到的原始红外图像需要经过各种硬件算法处理才能使用,而这些硬件算法受限于FPGA和DSP的系统资源上限往往需要进行必要的优化和精简,导致处理效果相较于上位机端同功能的软件算法大打折扣。提出了一种软硬件算法对比平台,通过全双工千兆网络联系上位机和硬件系统,定性对比移植后的硬件算法和上位机软件算法之间的差异,以此作为改善硬件移植后的算法的依据,并对硬件移植后算法的性能进行评价。主要做法为:首先通过千兆网络将探测器输出的原始红外视频源传输到上位机预存,进而上位机将预存的原始红外视频发给硬件处理板进行硬件算法处理并回接处理结果,最后上位机将预存的原始红外视频通过同功能软件算法处理后与硬件处理后的红外视频逐帧进行差值处理,定性得出硬件算法优劣。     

Interpolation-Free Fractional-Pixel Motion Estimation Algorithms with Efficient Hardware Implementation

This paper presents interpolation-free fractional-pixel motion estimation (FME) algorithms and efficient hardware prototype of one of the proposed FME algorithms. The proposed algorithms use a mathematical model to approximate the matching error at fractional-pixel locations instead of using the block matching algorithm to evaluate the actual matching error. Hence, no interpolation is required at fractional-pixel locations. The matching error values at integer-pixel locations are used to evaluate the mathematical model coefficients. The performance of the proposed algorithms has been compared with several FME algorithms including the full quarter-pixel search (FQPS) algorithm, which is used as part of the H.264 reference software. The computational cost and the performance analysis show that the proposed algorithms have about 90% less computational complexity than the FQPS algorithm with comparable reconstruction video quality (i.e., approximately 0.2 dB lower reconstruction PSNR values). In addition, a hardware prototype of one of the proposed algorithms is presented. The proposed architecture has been prototyped using the TSMC 0.18 μm CMOS technology. It has maximum clock frequency of 312.5 MHz, at which, the proposed architecture can process more than 70 HDTV 1080p fps. The architecture has only 13,650 gates. The proposed architecture shows superior performance when compared with several FME architectures.     

Power efficient range-free localization algorithm for wireless sensor networks

Considering energy consumption, hardware requirements, and the need of high localization accuracy, we proposed a power efficient range-free localization algorithm for wireless sensor networks. In the proposed algorithm, anchor node communicates to unknown nodes only one time by which anchor nodes inform about their coordinates to unknown nodes. By calculating hop-size of anchor nodes at unknown nodes one complete communication between anchor node and unknown node is eliminated which drastically reduce the energy consumption of nodes. Further, unknown node refines estimated hop-size for better estimation of distance from the anchor nodes. Moreover, using average hop-size of anchor nodes, unknown node calculates distance from all anchor nodes. To reduce error propagation, involved in solving for location of unknown node, a new procedure is adopted. Further, unknown node upgrades its location by exploiting the obtained information in solving the system of equations. In mathematical analysis we prove that proposed algorithm has lesser propagation error than distance vector-hop (DV-Hop) and other considered improved DV-Hop algorithms. Simulation experiments show that our proposed algorithm has better localization performance, and is more computationally efficient than DV-Hop and other compared improved DV-Hop algorithms.     

Investigation of radio channel uncertainty in distance estimation in wireless sensor networks

The distance estimation between nodes is a crucial requirement for localization and object tracking. Received signal strength (RSS) measurement is one of the used methods for the distance estimation in wireless networks. Its main advantage is that there are no additional hardware requirements. This paper describes a lateration approach for localization and distance estimation using RSS. For the purpose of investigation of RSS uncertainty, several scenarios were designed for both indoor and outdoor measurements. The first set of RSS measurement scenarios was proposed with the intention of hardware independent investigation of radio channel. For the second set of measurements, we employed IRIS sensor nodes to evaluate the distance estimation with certain devices. The experiments considered also obstacles in the radio channel. The results obtained in the proposed scenarios present usability of the method under different conditions. There is also a signal propagation model constructed from measured data at a node, which subsequently serves for distance determination.     

Quantifying relationship between relative position error of localization algorithms and object identification

Positioning of things, devices and people is the fundamental technology in ubiquitous computing. However, few literature has discussed the impact of positioning errors due to localization algorithm properties such as ranging noise and deployment of anchors on people’s identification of objects. Since several factors such as relative distance, relative angles and grouping of objects are intricately related with each other in such identification, it is not an easy task to investigate its characteristics. In this paper, we propose criteria to assess the “accuracy” of the estimated positions in identifying the objects. The criteria are helpful to design, develop and evaluate localization algorithms that are used to tell people the location of objects. Augmented reality is a typical example that needs such localization algorithms. To model the criteria without ambiguity, we prove that the Delaunay triangulation well-captures natural human behavior of finding similarity between estimated and true positions. We have examined different localization algorithms to observe how the proposed model quantifies the properties of those algorithms. Subjective testing has also been conducted using questionnaires to justify our quantification sufficiently renders human intuition.     

基于RSSI梯度的AP定位算法(英)

Recent rapid rise of indoor location based services for smartphones has further increased the importance of precise localization of Wi-Fi Access Point(AP).However,most existing AP localization algorithms either exhibit high errors or need specialized hardware in practical scenarios.In this paper,we propose a novel RSSI gradient-based AP localization algorithm.It consists of the following three major steps:firstly,it uses the local received signal strength variations to estimate the direction(minus gradient) of AP,then employs a direction clustering method to identify and filter measurement outliers,and finally adopts triangulation method to localize AP with the selected gradient directions.Experimental results demonstrate that the average localization error of our proposed algorithm is less than 2meters,far outperforming that of the weighted centroid approach.     

基于RSSI和惯性导航的融合室内定位算法

针对目前对高精度室内定位算法的需求,提出一种基于接收信号强度识别（RSSI）和惯性导航的融合室内定位算法。基于无线传感网中ZigBee节点的RSSI值,采用位置指纹识别算法,对网络中的未知节点进行定位。结合惯性传感单元（IMU）提供的惯性数据,对RSSI定位结果进行融合修正。利用Kalman滤波器,采用状态方程描述待定位节点位置坐标的动态变化规律,从而实现一种以无线传感网络定位为主、IMU为辅的融合定位方法。仿真结果表明,提出的融合定位算法既能改善单独使用RSSI定位受环境干扰较大的问题,又能避免单独使用惯性导航带来的累积误差,极大地提高了定位精度。     

Computational intelligence based localization of moving target nodes using single anchor node in wireless sensor networks

Wireless Sensor Networks (WSNs) have tremendous ability to interact and collect data from the physical world. The main challenges for WSNs regarding performance are data computation, prolong lifetime, routing, task scheduling, security, deployment and localization. In recent years, many Computational Intelligence (CI) based solutions for above mentioned challenges have been proposed to accomplish the desired level of performance in WSNs. Application of CI provides independent and robust solutions to ascertain accurate node position (2D/3D) with minimum hardware requirement (position finding device, i.e., GPS enabled device). The localization of static target nodes can be determined more accurately. However, in the case of moving target nodes, accurate position of each node in network is a challenging problem. In this paper, a novel concept of projecting virtual anchor nodes for localizing the moving target node is proposed using applications of Particle Swarm Intelligence, H-Best Particle Swarm Optimization, Biogeography Based Optimization and Firefly Algorithm separately. The proposed algorithms are implemented for range-based, distributed, non-collaborative and isotropic WSNs. Only single anchor node is used as a reference node to localize the moving target node in the network. Once a moving target node comes under the range of a anchor node, six virtual anchor nodes with same range are projected in a circle around the anchor node and two virtual anchor nodes (minimum three anchor nodes are required for 2D position) in surrounding (anchor and respective moving target node) are selected to find the 2D position. The performance based results on experimental mobile sensor network data demonstrate the effectiveness of the proposed algorithms by comparing the performance in terms of the number of nodes localized, localization accuracy and scalability. In proposed algorithms, problem of Line of Sight is minimized due to projection of virtual anchor nodes.     

一种新的AES算法的FPGA实现方法研究

文章主要讨论了高级加密标准(AES)算法在主频较低情况下的硬件实现.根据AES算法的结构特点和硬件实现的具体原理,提出了一种AES算法的硬件实现方法.该方法采用在单个时钟周期内执行多轮加密的策略,并使用流水线,做到了兼顾加密的速度和较低的时钟频率.最后,与现有的方法进行了分析比较.     

DV-Hop定位算法在随机传感器网络中的应用研究

DV-Hop节点定位算法是一种重要的与距离无关的定位算法。在各向同性的密集网络中,DV-Hop可以得到比较合理的定位精度,然而在随机分布的网络中,节点定位误差较大。该文根据DV-Hop算法定位过程,在平均每跳距离估计、未知节点到各参考节点之间距离的计算和节点位置估计方法等3个方面进行了改进,分析和仿真了不同改进措施和综合改进的定位性能。结果表明,与有关方法相比,该文提出的改进措施可极大地提高节点定位精度。此外,该文改进措施不改变DV-Hop算法的定位过程,因此不需要增加网络通信量和额外硬件支持,是理想的与距离无关算法。     

无线传感器网络用于监测系统中的定位算法

从硬件设计入手,介绍了自主设计的以片上系统（SOC）STM32W108为核心的WSN节点,在此基础上采用了一种基于RSSI的加权质心定位算法实现了节点的自定位。该算法将RSSI测距和质心定位算法相结合,用测得的RSSI值作为质心定位的加权因子,合理体现了不同锚节点对定位未知节点的约束力。通过测试证明,该定位方法在较少的通信开销情况下具有较高的定位精度,且易于实现。     

Hop-distance based addressing and routing for dense sensor networks without location information

One of the most challenging problems in wireless sensor networks is the design of scalable and efficient routing algorithms without location information. The use of specialized hardware and/or infrastructure support for localization is costly and in many deployment scenarios infeasible. In this study, the wave mapping coordinate (WMC) system to address the localization problem is introduced for dense sensor networks and a highly efficient routing algorithm applicable to WMC systems is proposed. The performance of the WMC system is evaluated through simulations and compared with the performance of geographic routing without location information (GWL). The WMC system is found to be highly scalable and efficient with a simple system set-up procedure. Simulation studies confirm the high routing performance of WMC systems which is comparable to the performance of greedy geographic routing with the availability of location information.     

An Overview of Power Analysis Attacks Against Field Programmable Gate Arrays

Since their introduction by Kocher in 1998, power analysis attacks have attracted significant attention within the cryptographic community. While early works in the field mainly threatened the security of smart cards and simple processors, several recent publications have shown the vulnerability of hardware implementations as well. In particular, field programmable gate arrays are attractive options for hardware implementation of encryption algorithms,but their security against power analysis is a serious concern, as we discuss in this paper. For this purpose, we present recent results of attacks attempted against standard encryption algorithms, provide a theoretical estimation of these attacks based on simple statistical parameters and evaluate the cost and security of different possible countermeasures.