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Source nodes in wireless image sensor networks transmit much more information than traditional scalar sensor networks, thereby demanding more energy of intermediate relaying nodes and putting energy efficiency as a key design issue. Intermediate nodes are usually interconnected by error-prone links where bit-errors are common, potentially degrading the application monitoring quality. When reliability is assured by retransmission mechanisms, higher packet error rates do not affect the application quality but result in additional energy consumption due to packet retransmission, even though many monitoring applications can tolerate some loss in the quality of the received image. DWT coding can decompose an image in data subbands, each one with different relevancies for the reconstruction of the original image at the receiver side. We propose an energy-efficient selective hop-by-hop retransmission mechanism where the reliability level of each packet is a function of the relevance of the payload data, according to the resulting subbands and the number of times a 2D DWT is applied over the images captured by the sensors’ cameras. In so doing, some lost packets are not retransmitted, saving energy of intermediate nodes with low impact to the quality of the reconstructed images. In order to estimate the benefits of this tradeoff between energy consumption and image quality, we designed a comprehensive energy consumption model and applied it in extensive mathematic simulations, providing substantial information about the mean performance of the proposed approach when compared with a fully-reliable transmission mechanism.

Wireless Image Sensor Networks (WISNs) consisting of untethered camera nodes and sensors may be deployed in a variety of unattended and possibly hostile environments to obtain surveillance data. In such settings, the WISN nodes must perform reliable event acquisition to limit the energy, computation and delay drains associated with forwarding large volumes of image data wirelessly to a sink node. In this work we investigate the event acquisition properties of WISNs that employ various techniques at the camera nodes to distinguish between event and non-event frames in uncertain environments that may include attacks. These techniques include lightweight image processing, decisions from n sensors with/without cluster head fault and attack detection, and a combination approach relying on both lightweight image processing and sensor decisions. We analyze the relative merits and limitations of each approach in terms of the resulting probability of event detection and false alarm in the face of occasional errors, attacks and stealthy attacks.

International audience; Wireless Image Sensor Networks (WISN) where sensor nodes are equipped with miniaturized visual CMOS cameras to provide visual information is a promising technology for situation awareness, search&rescue or intrusion detection applications. In this paper, we present an off-the-shelf image sensor based on Arduino boards with a CMOS uCamII camera. The image sensor works with raw 128x128 image, implements an image change detection mechanism based on simple-differencing technique and integrates a packet losstolerant image compression technique that can run on very limited memory platforms. We detail the performance and energy consumption measures of the various image platforms and highlight how both medium-end and low-end platforms can be supported. From the single-camera system, we describe the extension to a multi-camera system which provides omnidirectional sensing at a very lost cost for largescale deployment.

Wireless sensor networks are increasingly gaining attention. In recent years, a great deal of monitoring, control and tracking applications have been designed for different scenarios. For such networks, camera-enabled sensors can retrieve visual data from a monitored field, providing valuable information for many applications. In general, those networks have resource constraints of processing, memory, energy and transmission bandwidth, imposing many design challenges. Nevertheless, a group of applications may also have security requirements, which bring additional complexity to be handled. Most traditional security mechanisms for popular networks, like the Internet, are not suitable for wireless sensor networks, demanding proper investigation in this area. In this paper, we survey recent developments in encryption and privacy in wireless sensor networks deployed for transmissions of image snapshots, reviewing innovative approaches to provide different levels of security. Promising research directions are also discussed.