A survey of visual sensor network platforms <s>  <s> A wireless sensor network with multimedia capabilities typically consists of data sensor nodes, which sense, for instance, sound or motion, and video sensor nodes, which capture video of events of interest. In this survey, we focus on the video encoding at the video sensors and the real-time transport of the encoded video to a base station. Real-time video streams have stringent requirements for end-to-end delay and loss during network transport. In this survey, we categorize the requirements of multimedia traffic at each layer of the network protocol stack and further classify the mechanisms that have been proposed for multimedia streaming in wireless sensor networks at each layer of the stack. Specifically, we consider the mechanisms operating at the application, transport, network, and MAC layers. We also review existing cross-layer approaches and propose a few possible cross-layer solutions to optimize the performance of a given wireless sensor network for multimedia streaming applications. <s> BIB001 </s> A survey of visual sensor network platforms <s>  <s> Wireless sensor networks are an important research area that has attracted considerable attention. Most of this attention, however, has been concentrated on WSNs that collect scalar data such as temperature and vibration. Scalar data can be insufficient for many applications such as automated surveillance and traffic monitoring. In contrast, camera sensors collect visual data, which are rich in information and hence offer tremendous potential when used in WSNs. However, they raise new challenges such as the transmission of visual data with high computational and bandwidth requirements in mainly low-power visual sensor networks. In this article we highlight the challenges and opportunities of VSNs. We discuss major research issues of VSNs, specifically camera coverage optimization, network architecture, and low-power visual data processing and communication, and identify enabling approaches in this area. <s> BIB002 </s> A survey of visual sensor network platforms <s>  <s> Visual sensor networks have emerged as an important ::: class of sensor-based distributed intelligent systems, ::: with unique performance, complexity, and quality of service ::: challenges. Consisting of a large number of low-power camera nodes, ::: visual sensor networks support a great number of novel ::: vision-based applications. The camera nodes provide information ::: from a monitored site, performing distributed and collaborative ::: processing of their collected data. Using multiple cameras in the ::: network provides different views of the scene, which enhances ::: the reliability of the captured events. However, the large amount ::: of image data produced by the cameras combined with the ::: network's resource constraints require exploring new means ::: for data processing, communication, and sensor management. ::: Meeting these challenges of visual sensor networks requires ::: interdisciplinary approaches, utilizing vision processing, communications ::: and networking, and embedded processing. In this ::: paper, we provide an overview of the current state-of-the-art in ::: the field of visual sensor networks, by exploring several relevant ::: research directions. Our goal is to provide a better understanding ::: of current research problems in the different research fields of ::: visual sensor networks, and to show how these different research ::: fields should interact to solve the many challenges of visual sensor ::: networks. <s> BIB003 </s> A survey of visual sensor network platforms <s>  <s> Small low-cost multimedia sensors ubiquitously capture and transmit multimedia information from fields to central stations in support of applications. However, Multimedia sensors in Wireless Multimedia Sensor Networks (WMSNs), have limited resources in terms of their computational capability, memory capability, bandwidth, and battery power, which hinder a wide application of WMSNs. The challenges, issues and solutions in WMSNs regarding QoS, energy efficiency and security have been recently studied. It is highly desirable to incorporate the characteristics of multimedia and information security at the application layer into adaptation and optimization at lower layers in a cross-layer approach. In this paper, we conducted a survey on the recent development of the cross-layer design in WMSNs. Based on our studies, we concluded that that cross-layer approaches are promising solutions and can efficiently support future multimedia application in WMSNs. <s> BIB004
High-resolution images and videos require complex compression and coding algorithms and high bandwidth usage. These requirements imply that visual sensor nodes dissipate significantly higher power than scalar sensor nodes. Furthermore, sensors used in relaying data traffic have to be capable of buffering large number of packets. To reduce the bandwidth utilization, visionprocessing techniques capable of reducing the amount of traffic by intelligently manipulating the raw data can be used at the cost of allocating more computation resources. Main motivations of this study are two-folds. First, we discuss and compare VSN platforms based on processing and vision computing techniques. VSNs are distinguished from WSNs by their capability to present information-rich visual data, however, effective use of visual data depends on the use of appropriate processing techniques. There are differences in the techniques implemented or realizable in current VSN platforms because technical challenges involve many design trade-offs and decisions are usually enforced by hardware limitations and energy constraints. Second, we investigate the capabilities and limitations of VSN platforms in detail. We believe that protocol, algorithm, and application development for VSNs cannot be of practical use unless the underlying enabling technologies and platforms are well understood. Other surveys (such as BIB002 BIB003 ) give a more general perspective on VSNs. We refer readers interested in specific VSN topics which are not in the scope of our survey to other relevant surveys in the literature written on various aspects of VSNs (general overview BIB003 , challenging issues BIB002 , multimedia streaming BIB001 , security  , cross-layer design BIB004 ). The rest of this paper is organized as follows: Section 2 presents the reasons for designing special platforms for VSN applications. Section 3 provides an overview of image compression, video coding, and vision computing techniques used in VSN platforms. Section 4 presents an overview of the currently available VSN platforms. Section 5 categorizes these platforms according to integration level, data processing hardware, energy dissipation, radios, operating system and software architecture, hierarchy, and applications. We present a critical evaluation of VSN platforms and discuss open problems in Section 6. Section 7 presents conclusions of this survey.