Visual sensor networks for infomobility

Wireless visual sensor network (VSN) can be said to be a special class of wireless sensor network (WSN) with smart-cameras. Due to its visual sensing capability, it has become an effective tool for applications such as large area surveillance, environmental monitoring and objects tracking. Different from a conventional WSN, VSN typically includes relatively expensive camera sensors, enhanced flash memory and a powerful CPU. While energy consumption is dominated primarily by data transmission and reception, VSN consumes extra power onimage sensing, processing and storing operations. The well-known energy-hole problem of WSNs has a drastic impact on the lifetime of VSN, because of the additional energy consumption of a VSN. Most prior research on VSN energy issues are primarily focusedon a single device or a given specific scenario. In this paper, we propose a novel optimal two-tier deployment strategy for a large scale VSN. Our two-tier VSN architecture includes tier-1 sensing network with visual sensor nodes (VNs) and tier-2 network having only relay nodes (RNs). While sensing network mainly performs image data collection, relay network only for wards image data packets to the central sink node. We use uniform random distribution of VNs to minimize the cost of VSN and RNs are deployed following two dimensional Gaussian distribution so as to avoid energy-hole problem. Algorithms are also introduced that optimizes deployment parameters and are shown to enhance the lifetime of the VSN in a cost effective manner.

Recently much research has been conducted in visual sensor networks. Compared to traditional sensor networks, vision networks differ in various aspects such as the amount of data to be processed and transmitted, the requirements on quality-of-service, and the level of collaboration among the sensor nodes. This paper deals with sensor fusion on visual sensor networks. We focus here on methods for fusing data from various distributed sensors and present a generic framework for fusion on embedded sensor nodes. This paper extends our previous work on distributed smart cameras and presents our approach toward the transformation of smart cameras into a distributed, embedded multisensor network. Our generic fusion model has been completely implemented on a distributed embedded system. It provides a middleware which supports automatic mapping of our fusion model to the target hardware. This middleware features dynamic reconfiguration to support modification of the fusion application at runtime without loss of sensor data. The feasibility and reusability of the I-SENSE concept is demonstrated with experimental results of two case studies: vehicle classification and bulk good separation. Qualitative and quantitative benefits of multilevel information fusion are outlined in this article.

A prediction-based approach for features aggregation in Visual Sensor Networks

Visual Sensor Networks (VSNs), formed by large number of low-cost, small-size visual sensor nodes, represent a new trend in surveillance and monitoring practices. Sensor collaboration is essential to VSNs and normally performed among sensors having similar measurements. The directional sensing characteristics of imagers and the presence of visual occlusion present unique challenges to neighborhood formation, as geographically-close neighbors might not monitor similar scenes. In this paper, we propose the concept of forming semantic neighbors, where collaboration is only performed among geographically-close nodes that capture similar images, thus requiring image comparison as a necessary step. To avoid large amount of data transfer, we propose feature-based image comparison as features provide more compact representation of the image. The paper studies several representative feature detectors and descriptors, in order to identify a suitable feature-based image comparison system for the resource-constrained VSN. We consider two sets of metrics from both the resource consumption and accuracy perspectives to evaluate various combinations of feature detectors and descriptors. Based on experimental results obtained from the Oxford dataset and the MSP dataset, we conclude that the combination of Harris detector and moment invariants presents the best balance between resource consumption and accuracy for semantic neighbor formation in VSNs.

Cooperative image analysis in visual sensor networks

During the last decade, visual monitoring has gained an increasing interest especially in the field of smart cities and intelligent transportation systems. This paper describes a feature-based vehicle tracking system in visual sensor networks at roundabouts. In the proposed system, the tasks for vehicle tracking are divided among smart camera nodes and the receiver. Smart camera nodes are embedded devices equipped with camera sensor, multiprocessors for video processing and computer vision tasks, and an RF transceiver for wireless communication. They are responsible for the vehicle detection and classification as well as features extraction. In order to satisfy the constraints of the visual sensor network in terms of power and communication resources, we assume that only the features are transmitted to the sink node. The received features will then be used to retrieve the vehicle trajectories. In order to train the vehicle classifier used at the camera nodes and to test the proposed tracking approach, a training database was built by placing cameras around a realworld roundabout. The system is shown to be capable of tracking vehicles even in partial occlusion cases.

Nowadays visual sensor networks are used in emergency or time of surveillance of remote area where human reach is not possible. There situations arise when mobility of nodes is required in visual sensor network. In this paper we considers mobility of visual sensor nodes and tries to maximize the lifetime of network using priority if nodes. We use hierarchical and heterogeneous architecture for deploying nodes. In this we use two types of nodes. On this architecture we use prioritized scheduling technique to maximize the lifetime of network. Result shows lifetime is increased compare to the stationary nodes as after same time we get more live sensors than stationary system.

Technology is quickly revolutionizing our everyday lives, helping us to perform complex tasks. The Internet of Things (IoT) paradigm is getting more and more popular and is key to the development of Smart Cities. Among all the applications of IoT in the context of Smart Cities, real-time parking lot occupancy detection recently gained a lot of attention. Solutions based on computer vision yield good performance in terms of accuracy and are deployable on top of visual sensor networks. Since the problem of detecting vacant parking lots is usually distributed over multiple cameras, adhoc algorithms for content acquisition and transmission are to be devised. A traditional paradigm consists in acquiring and encoding images or videos and transmitting them to a central controller, which is responsible for analyzing such content. A novel paradigm, which moves part of the analysis to sensing devices, is quickly becoming popular. We propose a system for distributed parking lot occupancy detection based on the latter paradigm, showing that onboard analysis and transmission of simple features yield better performance with respect to the traditional paradigm in terms of the overall rate-energy-accuracy performance.

Video sensor networks (VSN) offer an interesting platform for a distributed and flexible surveillance system. In such a system, video compression and wireless transmission are the major operations on each video node. For a battery-powered wireless video sensor, it is essential to maximize the power efficiency of these two operations. Currently, H.264/AVC is the most widely used ITU-T and ISO/IEC video coding standard. Previous works on determining the trade-off between compression and transmission that minimizes energy consumption consider oversimplified coding configurations, thus not taking full advantage of the flexibility and advanced features of H.264/AVC. Choosing the right configuration and setting parameters that lead to optimal encoding performance is of prime importance for video sensor network (VSN) applications, especially since VSN is constrained in terms of bandwidth and energy resources. This paper studies the relationship between the picture quality, the transmission rate, and the complexity of the encoder to expound the energy consumption trade-off between encoding and transmission in VSN. The results of our study can be used as guidelines in optimizing the overall power consumption of a VSN system as it detailed in the paper.

Aiming at the complexity of the network transmission environment and the decentralization of the monitoring sites in the middle route of the South to North Water Diversion Project, this article presents a water conservancy monitoring architecture based on the visual sensor networks. First, a network assessment method is proposed to evaluate the sensor networks condition, and the encoder is adjusted with the result of the sensor networks condition evaluation. Then, based on distributed database architecture and visualization system construction, a three-level structure of the water conservancy monitoring system is designed and built. The experiment results show that the water conservancy monitoring system proposed in this article meets the transmission requirement under the complex sensor networks condition of water conservancy project. The water conservancy monitoring system has been applied to the middle route of the South to North Water Diversion Project, which achieves the needs of engineering applications.

This paper is to study the tracking of mobile objects and associated coverage problems in visual sensor networks. When sensors equipped with cameras are randomly deployed in a monitoring environment, many cameras are involved in covering the same mobile object. Images of the object may be captured by different camera nodes in different orientations simultaneously, and the captured images are then sent back to a base station or server. However, achieving characteristic point coverage of objects invariably involves a great deal of redundant image data consuming the transmission energy of the visual sensor network. One approach is proposed to overcome this problem. The minimum number of camera nodes required for set coverage can be determined by predicting the direction and speed of the mobile object. The simulation results show that this protocol reduces transmission cost while preserving the maximum coverage range of mobile objects.

This paper presents a new hybrid and parallel processing image fusion technique for multi-focus images. Here, two different methods are used i.e. Stationary Wavelet Transform (SWT) and Principal Component Analysis (PCA) that are implemented on the input images in parallel. These two methods are applied on same input dataset. This method is although computationally bit slower than the compared method but still it shows better results. The fused images obtained from the SWT and PCA are later again fused using PCA method. This is a parallel processing technique. The result of proposed method is compared with other traditional and conventional methods like DWT, SWT and PCA. It is observed that the result of proposed method is better than the compared methods. The result of the proposed method is analyzed qualitatively (visual appearance) and quantitatively using CC (Correlation Coefficient), UIQI (Universal Image Quality Index), and PSNR (Peak Signal-to-Noise Ratio). The proposed technique will have the capability to be implemented in real time applications of Visual Sensor Network (VSN).

When visual sensor networks (VSNs) enter daily life in society, they not only bring great convenience but also cause people to worry about privacy. Traditional image encryption uses the snowflake effect to protect the privacy, but this can compromise the usability of directly browsing images captured by nodes in VSNs. Recently, thumbnail-preserving encryption (TPE) has been proposed to balance image usability and privacy. However, the Markov chain’s limited connectivity and high time cost, which result in low efficiency, may preclude its application in VSNs. Motivated by this, we propose a novel TPE scheme to protect the image collected in VSNs’ privacy efficiently. We first deeply study the bijective relationship between the three-pixel group and its rank, and then propose a new number method for both, based on which we design the efficient rank mapping. Subsequently, an efficient thumbnail-preserving image encryption via three-pixel rank mapping (E-TPE) is designed, achieving NR security and enhancing the Markov chain’s connectivity. The experiments demonstrate the scheme’s efficiency; that is, it is currently the quickest ideal-TPE scheme with NR security, and a good balance is achieved between usability and privacy.

Recent developments in image and video technologies enabled easy access to a new type of sensor-based networks, Visual Sensor Networks (VSN). VSNs are gaining a lot of attention lately. They are used in several applications including surveillance and telepresence. They consist of several low-cost, low-power visual nodes with sensing, data processing, and communication capabilities. These tiny nodes are able to collect large volumes of images, process them, and send extracted data to each other and to the base station for further analysis. Unfortunately, the huge amount of data captured and processed is faced with the limited resources of such platforms. There are several challenges involved with the design and implementation of VSNs. This chapter presents an overview of visual nodes, architectures, and challenges. It also reviews available VSN platforms and compares their processing capabilities, highlighting the need for new lightweight but efficient image processing algorithms and architectures.

In this work, we propose the cubature Kalman filter (CKF) based distributed object tracking algorithm in a visual sensor network (VSN). A VSN consists of several distributed smart cameras having the ability to process and analyze the retrieved data locally. The first objective is to optimize the tracking process within the VSN through the CKF. Under the conditions of non-linear motion and observation model, the CKF based method features a considerably better tracking accuracy than the extended Kalman filter (EKF) based method in terms of the mean square error (MSE). Although, the particle filter (PF) based method shows better performance than the CKF, it is computationally very complex. The second objective is to optimize the object tracking by aggregating the tracking results from multiple cameras. Assuming the VSN is a multi-camera network with overlapping field of views (FOVs), cameras having the same object in their FOV exchange their local estimates of the object's position and velocity. During the estimation process, each of the participating cameras aggregates the received states via a consensus algorithm. Thus, the object's real state is more accurately predicted by the resulting joint state than it would be by processing only a single camera's observation.