A combined decision fusion and channel coding scheme for distributed fault-tolerant classification in wireless sensor networks

In this paper, we consider the distributed classification problem in wireless sensor networks. Local decisions made by local sensors, possibly in the presence of faults, are transmitted to a fusion center through fading channels. Classification performance could be degraded due to the errors caused by both sensor faults and fading channels. Integrating channel decoding into the distributed fault-tolerant classification fusion algorithm, we obtain a new fusion rule that combines both soft-decision decoding and local decision rules without introducing any redundancy. The soft decoding scheme is utilized to combat channel fading, while the distributed classification fusion structure using error correcting codes provides good sensor fault-tolerance capability. Asymptotic performance of the proposed approach is also investigated. Performance evaluation of the proposed approach with both sensor faults and fading channel impairments is carried out. These results show that the proposed approach outperforms the system employing the MAP fusion rule designed without regard to sensor faults and the multiclass equal gain combining fusion rule     

多级式多传感器信息融合中的状态估计

本文多级式传感器监视系统中的状态估计技术,基于背地里传感器Ｋａｌｍａｎ滤波方程,两级集中和分布估计解,本文提出多坐标系中多级式多传感器跟踪系统的三层集中估计方法,在不同笛卡尔坐标系中,本文提出了几种适合于三层多传感器信息融合系统的航迹级融合方法,其中既包括了集－分估计,也包括了分－分估计组合问题,在离散线性假设下,各层估计解都是最优的并且对同一问题的不同表现形式是等价的,另外,文中还给出多级式多传     

容积卡尔曼一致滤波

针对卡尔曼一致滤波的应用受限于被估计系统需 满足线性条件的问题,通过容积卡尔曼滤波(CKF)和一致性策 略的动态结合,提出一种容积卡尔曼一致滤波(CKCF)算法。算法采用分布式融合机制, 传感器节点采集可通信相邻 节点的信息,并作为自身节点的量测信息应用于CKF,获取局部状态估计 值。在此基础上,利用一 致性策略实现对整个量测系统中传感器节点局部估计值的优化,进而通过增强传感器节点估 计值一致性实现目标 状态估计精度的提升。相对于标准卡尔曼一致滤波,本文算法将一致性策略推广到非线性系 统估计领域。理论分析 与仿真实验验证了算法的可行性与有效性。     

带反馈信息的多传感器分层估计算法

为了改善局部节点和传感器级的跟踪性能,本文研究带反馈信息的多级式多传感器系统中的状态估计技术.在给出有反馈信息情况下传感器级状态估计解的基础上,本文提出多坐标系中有反馈信息的两层集中、分布和混合估计方程.在不同笛卡尔坐标系中,本文提出了几种带反馈信息的三层多传感器系统中的航迹级融合方法,其中包括集-分估计、分-分估计和混-分估计,并以定理的形式证明有、无反馈信息情况下的两类三层状态估计是等价的、最优的.仿真结果表明,在多传感器信息融合系统中引入反馈机制可以明显改善一些局部节点和传感器级的跟踪精度.     

Smart Phone Based Sensor Fusion by Using Madgwick Filter for 3D Indoor Navigation

In this paper, we proposed an enhanced pedestrian dead reckoning (PDR) system based on sensor fusion schemes using a smartphone. PDR is an effective technology for 3D indoor navigation. However, still, there are some obstacles to be overcome in its practical application. To track and simulate pedestrian’s position, which is confronted by environmental errors, walls, Bayesian errors, and other obstacles, our proposed PDR system enables estimation of stride based on the vertical accelerometer data and orientation from sensor fusion technique of magnetic angular rate and gravity sensor data by Madgwick filter. This localization system is independent of the received signal strength-based fingerprinting system. In addition, to estimate the current floor level, we make use of barometer information. To collect ground truth accurately and efficiently a prototype is implemented with the benchmark. We perform the same distance estimation for four different pedestrians to evaluate the accuracy of the proposed system. The real indoor experimental results demonstrate that the proposed system performs well while tracking the test subject in a 2D scenario with low estimation error (< 2 m). The 3D evaluation of the system inside a multi-story building shows that high accuracy can be achieved for a short range of time without position update from external sources. Then we compared localization performance between our proposed system and an existing (extended Kalman filter based) system.

     

多光电跟踪设备异步序贯分布式目标跟踪算法

针对多光电跟踪设备组网后出现的异步测量问题，提出了一种异步分布式序贯目标跟踪算法。该算法由局部滤波器和融合滤波器构成，先利用状态转换方法，将多光电跟踪设备节点及其邻节点的异步测量对齐到融合时刻，得到拟测量方程。随后，利用射影原理对拟测量方程和目标运动状态方程构成的目标跟踪系统，提出异步序贯局部滤波器来计算较为精确的局部滤波值。再以协方差交叉算法为基础，提出基于扩散策略的融合滤波器，对局部估计值进行融合计算，来提高目标跟踪精度，并降低组网后各光电跟踪设备节点融合估计值的差异程度。最后对所提出的算法进行了仿真实验，以验证其有效性。     

Calibrating Distributed Camera Networks

Recent developments in wireless sensor networks have made feasible distributed camera networks, in which cameras and processing nodes may be spread over a wide geographical area, with no centralized processor and limited ability to communicate a large amount of information over long distances. This paper overviews distributed algorithms for the calibration of such camera networks- that is, the automatic estimation of each camera's position, orientation, and focal length. In particular, we discuss a decentralized method for obtaining the vision graph for a distributed camera network, in which each edge of the graph represents two cameras that image a sufficiently large part of the same environment. We next describe a distributed algorithm in which each camera performs a local, robust nonlinear optimization over the camera parameters and scene points of its vision graph neighbors in order to obtain an initial calibration estimate. We then show how a distributed inference algorithm based on belief propagation can refine the initial estimate to be both accurate and globally consistent.      

Distributed Weighted Fusion Estimators with Random Delays and Packet Dropping

This paper is concerned with the distributed fusion estimation in sensor networks where local estimates are sent to a fusion centre for fusion estimation, with random delays and packet dropouts. Under the linear minimum variance sense, a distributed optimal weighted fusion estimator is given for discrete time-invariant stochastic linear systems with multiple distributed sensors. The algorithm involves a weighted fusion of local predictors with different prediction steps from different sensor sources. A recursive computation of the cross-covariance matrix of prediction errors between any two local estimates is derived. We present two fusion strategies. One is to fuse the latest local estimates that reach the fusion centre at the current time. The other is to fuse the latest local estimates that reach the fusion centre at the current time and the predicted estimates of those that do not have estimates received at the current time. Further, to reduce the computation cost, only the local estimates satisfying the given precision requirement are fused because those with longer delays or consecutive packet dropouts have large estimation errors. A strategy to select local estimators for fusion is presented based on gate thresholds of time delays or the numbers of consecutive packet dropouts for all local estimators. This method can be implemented offline. Simulation for a tracking system with four sensors shows the effectiveness of the proposed approaches.     

基于贝叶斯理论的分布式多视角目标跟踪算法

 为了有效解决传统单视角跟踪难于处理的目标遮挡问题,本文提出了一种分布式多视角目标跟踪算法. 该算法首先基于贝叶斯理论,为多视角目标跟踪问题建立了分布式数据融合的概率框架;并利用粒子滤波器对所需后验概率进行近似,提出了自适应的观测模型和状态转移模型. 各摄像机能够并行化地进行数据采集、处理、融合,而无需集中式处理单元;能够有效避免遮挡造成的误差传递,提高跟踪算法的鲁棒性. 实验证明了本文算法的有效性.     

Optimality Properties,Closed-Form Parameterizations and Distributed Strategy of the Two-User MISO Interference Channel

In this paper, the closed-form parameterizations to the Pareto boundary for the two-user multiple-input single-output interference channel are studied. Firstly, for the equivalent channel model with each transmitter having only two antennas, the weighted sum-rate maximization (WSRMax) problem is reformulated with newly defined angle variables. Then, a centralized weighted leakage-plus-noise-to-signal ratio minimization (WLNSRMin) algorithm is proposed to find a locally optimal weighted sum-rate point. Each step of the algorithm is solved by evaluating closed-form expressions. A distributed algorithm is also given to avoid the exchange of the channel state information (CSI) between transmitters. Numerical results show that the centralized WLNSRMin algorithm converges to a local optimum of the WSRMax problem after a few iterations and the distributed algorithm achieves a performance very close to that of the centralized algorithm with only local CSI.

     

基于航迹隶属度的分布式系统数据融合算法

航迹关联与航迹融合是分布式目标跟踪系统数据融合的关键.本文研究了基于航迹隶属度的数据融合算法.综合各传感器航迹估计形成的目标运动状态特征向量与传感器分辨率,根据模糊聚类算法建立各观测时刻航迹隶属度矩阵与系统航迹关联决策矩阵,解决融合中心航迹关联问题.根据加权融合算法思想,结合各观测时刻航迹隶属度矩阵,实时、动态分配航迹号集合中各局部航迹权值,解决目标航迹融合问题.蒙特卡罗仿真表明,算法航迹关联效果明显优于加权航迹关联算法,并得到与简单航迹融合算法一致的目标融合航迹.     

Distributed fusion architectures and algorithms for target tracking

Modern surveillance systems often utilize multiple physically distributed sensors of different types to provide complementary and overlapping coverage on targets. In order to generate target tracks and estimates, the sensor data need to be fused. While a centralized processing approach is theoretically optimal, there are significant advantages in distributing the fusion operations over multiple processing nodes. This paper discusses architectures for distributed fusion, whereby each node processes the data from its own set of sensors and communicates with other nodes to improve on the estimates, The information graph is introduced as a way of modeling information flow in distributed fusion systems and for developing algorithms. Fusion for target tracking involves two main operations: estimation and association. Distributed estimation algorithms based on the information graph are presented for arbitrary fusion architectures and related to linear and nonlinear distributed estimation results. The distributed data association problem is discussed in terms of track-to-track association likelihoods. Distributed versions of two popular tracking approaches (joint probabilistic data association and multiple hypothesis tracking) are then presented, and examples of applications are given.     

An isotropic universal decentralized estimation scheme for a bandwidth constrained ad hoc sensor network

Consider a decentralized estimation problem whereby an ad hoc network of K distributed sensors wish to cooperate to estimate an unknown parameter over a bounded interval [-U,U]. Each sensor collects one noise-corrupted sample, performs a local data quantization according to a fixed (but possibly probabilistic) rule, and transmits the resulting discrete message to its neighbors. These discrete messages are then percolated in the network and used by each sensor to form its own minimum mean squared error (MMSE) estimate of the unknown parameter according to a fixed fusion rule. In this paper, we propose a simple probabilistic local quantization rule: each sensor quantizes its observation to the first most significant bit (MSB) with probability 1/2, the second MSB with probability 1/4, and so on. Assuming the noises are uncorrelated and identically distributed across sensors and are bounded to [-U,U], we show that this local quantization strategy together with a fusion rule can guarantee a MSE of 4U/sup 2//K, and that the average length of local messages is bounded (no more than 2.5 bits). Compared with the worst case Cramer-Rao lower bound of U/sup 2//K (even for the centralized counterpart), this is within a factor of at most 4 to the minimum achievable MSE. Moreover, the proposed scheme is isotropic and universal in the sense that the local quantization rules and the final fusion rules are independent of sensor index, noise distribution, network size, or topology. In fact, the proposed scheme allows sensors in the network to operate identically and autonomously even when the network undergoes changes in size or topology.     

多传感器和数据融合(续)

文中介绍了多传感器集成及数据融合的概念、优点、结构、方法和应用,列举了传感器四种不同集成度的特点。数据融合把来自不同传感器或其它信息源的数据加以综合、相关、互联,以便提高定位和特征估计的精度。在数据融合过程中建模包括信号模型、噪声模型、变换器模型、数据变换模型以及融合模型。数据融合模型包括事例的方法和结构,文章介绍了集成式、分布式和混合式融合结构,并进行了比较。此外,还介绍了国外一些数据融合的试验     

多传感器和数据融合(一)

文中介绍了多传感器集成及数据融合的概念、优点、结构、方法和应用,列举了传感器四种不同集成度的特点。数据融合把来自不同传感器的、或其它信息源的数据加以综合、相关、互联,以便提高定位和特征估计的精度。在数据融合过程中建模包括信号模型、噪声模型、变换器模型、数据变换模型以及融合模型。数据融合模型包括融合的方法和结构,文章介绍了集成式、分布式和混合式融合结构,并对它们进行了比较。此外,还介绍了国外一些数据融合的试验系统,商业软件和应用的例子。     

基于Chan算法的水下测控设备组网数据融合技术研究

依据水下测控设备组网系统的工作特点,为了有效挖掘现有测控设备的使用效能,构建高精度的综合性水下测控网络,该文提出基于Chan算法的水下测控设备组网集中式数据融合定位算法。该算法首先利用基于波达时间的加权最小二乘算法粗测目标位置,然后依据该目标位置和测量时延信息的关系,构造新的误差矢量,利用该误差矢量再次加权最小二乘估计解算目标位置。研究结果表明,该算法可实现多套水下测控设备的数据融合,可有效提高全域范围的定位精度,且精度高于纯基于波达时间的融合定位算法。     

Decentralized estimation in an inhomogeneous sensing environment

We consider decentralized estimation of a noise-corrupted deterministic parameter by a bandwidth-constrained sensor network with a fusion center. The sensor noises are assumed to be additive, zero mean, spatially uncorrelated, but otherwise unknown and possibly different across sensors due to varying sensor quality and inhomogeneous sensing environment. The classical best linear unbiased estimator (BLUE) linearly combines the real-valued sensor observations to minimize the mean square error (MSE). Unfortunately, such a scheme cannot be implemented in a practical bandwidth-constrained sensor network due to its requirement to transmit real-valued messages. In this paper, we construct a decentralized estimation scheme (DES) where each sensor compresses its observation to a small number of bits with length proportional to the logarithm of its local signal-to-noise ratio (SNR). The resulting compressed bits from different sensors are then collected and combined by the fusion center to estimate the unknown parameter. The proposed DES is universal in the sense that each sensor compression scheme requires only the knowledge of local SNR, rather than the noise probability distribution functions (pdf), while the final fusion step is also independent of the local noise pdfs. We show that the MSE of the proposed DES is within a constant factor of 25/8 of that achieved by the classical centralized BLUE estimator.     

Estimation of Nonlinear Wireless Channel Based on Incremental Spline Adaptive Filtering

Channel estimation in a wireless sensor network is imperative to error-free information dissemination and data collection. The estimation procedure is challenging if there exists a nonlinear distortion to the communication signal due to the radio-frequency components in the transmitting or receiving entity. It has drawn attention to nonlinear system modeling for channel estimation, where lately, one of the most important methods has been spline adaptive filter (SAF). The necessity of updating both linear filter coefficients and nonlinear control points makes the adaptation process slow. Hence, we propose an incremental spline adaptive filter using the least mean square algorithm (ISAF-LMS), which acquires faster convergence while estimating non-linearity along with linear filter coefficients. The steady-state performance of the proposed method is carried out by following the energy conservation approach. The simulation result shows faster convergence in the distributed case than in non-cooperative estimation. Further, the performance is compared with diffusion SAF and incremental version of conventional Volterra adaptive filter-based nonlinear channel estimation (IVLMS). The proposed algorithm performance is better than IVLMS.

     

多传感器网络系统基于无序估计的分布式信息融合

无线传感器网络的局部节点往融合中心传输信息时,不确定的随机延迟易使得信息无序现象频繁发生,从而导致传统信息融合方法的应用面临诸多难题和挑战。该文以带有任意随机延迟的多传感器同步采样系统为对象,研究无序估计(“Out-Of-Sequence” Estimate, OOSE)信息系统的最优分布式融合问题,最终建立一种新型的通用最优OOSE融合算法。与现有基于集中式框架的无序量测融合方法相比,新算法在融合精度和算法复杂度上均具有显著优势。算法分析和计算机仿真验证了新算法的有效性和优越性。     

Sensor node-assisted asynchronous cooperative spectrum sensing for cognitive radio network

In order to take advantage of the asynchronous sensing information, alleviate the sensing overhead of secondary users （SUs） and improve the detection performance, a sensor node-assisted asynchronous cooperative spectrum sensing （SN-ACSS） scheme for cognitive radio （CR） network （CRN） was proposed. In SN-ACSS, each SU is surrounded by sensor nodes （SNs）, which asynchronously make hard decisions and soft decisions based on the Bayesian fusion rule instead of the SU. The SU combines these soft decisions and makes the local soft decision. Finally, the fusion center （FC） fuses the local soft decisions transmitted from SUs with different weight coefficients to attain the final soft decision. Besides, the impact of the statistics of licensed band occupancy on detection performance and the fact that different SNs have different sensing contributions are also considered in SN-ACSS scheme. Numerical results show that compared with the conventional synchronous cooperative spectrum sensing （SCSS） and the existing ACSS schemes, SN-ACSS algorithm achieves a better detection performance and lower cost with the same number of SNs.