Cristian Duran-Faundez

Tiny block-size coding for energy-efficient image compression and communication in wireless camera sensor networks

This article presents a lightweight image compression algorithm explicitly designed for resource-constrained wireless camera sensors, called TiBS (tiny block-size image coding). TiBS operates on blocks of 2x2 pixels (this makes it easy for the end-user to conceal missing blocks due to packet losses) and is based on pixel removal. Furthermore, TiBS is combined with a chaotic pixel mixing scheme to reinforce the robustness of image communication against packet losses. For validation purposes, TiBS as well as a JPEG-like algorithm have been implemented on a real wireless camera sensor composed of a Mica2 mote and a Cyclops imager. The experimental results show that TiBS does not provide high compression ratios, but it enables energy-efficient image communication, even for the source camera node, and even for high packet loss rates. Considering an original 8-bpp grayscale image for instance, the amount of energy consumed by the Cyclops/Mica2 can be reduced by around 60% when the image is compressed using TiBS, compared to the scenario without compression. Moreover, the visual quality of reconstructed images is usually acceptable under packet losses conditions up to 40-50%. In comparison, the JPEG-like algorithm results in clearly more energy consumption than TiBS at similar image quality and, of course, its resilience to packet losses is lower because of the larger size of encoded blocks. Adding redundant packets to the JPEG-encoded data packets may be considered to deal with packet losses, but the energy problem remains.

Error resilient image communication with chaotic pixel interleaving for wireless camera sensors

New applications of wireless sensor networks require vision capabilities. Considering the high loss rates found in sensor networks, and the limited hardware resources of current sensor nodes, low-complexity robust image transmission must be implemented, avoiding as much as possible the need for retransmission or redundancy. In this paper we propose a pixel interleaving scheme based in Torus Automorphisms, thus, neighboring pixels are transmitted in different packets. Hence, if packets are lost, we have a high probability of retrieving enough information to obtain an approximation of the original value. Results show an increase of the image quality in comparison with a sequential raw image transmission approach, while preserving similar energy consumptions, time and low-complexity.

A Fuzzy-Based Approach for Sensing, Coding and Transmission Configuration of Visual Sensors in Smart City Applications

The advance of technologies in several areas has allowed the development of smart city applications, which can improve the way of life in modern cities. When employing visual sensors in that scenario, still images and video streams may be retrieved from monitored areas, potentially providing valuable data for many applications. Actually, visual sensor networks may need to be highly dynamic, reflecting the changing of parameters in smart cities. In this context, characteristics of visual sensors and conditions of the monitored environment, as well as the status of other concurrent monitoring systems, may affect how visual sensors collect, encode and transmit information. This paper proposes a fuzzy-based approach to dynamically configure the way visual sensors will operate concerning sensing, coding and transmission patterns, exploiting different types of reference parameters. This innovative approach can be considered as the basis for multi-systems smart city applications based on visual monitoring, potentially bringing significant results for this research field.

Energy consumption analysis of a simple image transmission protocol in wireless sensor networks

This paper proposes and evaluates a simple energyaware image transmission protocol suitable for wireless sensor networks. Energy saving is achieved through the use of a wavelet image transform and a semi-reliable transmission. On the one hand, wavelet image transform provides data decomposition in multiple levels of resolution, so the image can be divided into packets with different priorities. On the other hand, semi-reliable transmission enables priority-based packet discarding by intermediate nodes according to their battery’s state-of-charge. Such approach provides a graceful trade-off between the image quality played out and the sensor nodes lifetime. An analytical performance evaluation in terms of mean dissipated energy is performed. Results show up to 90% reduction in the energy consumption achieved by our proposal compared to a non energy-aware transmission.

Sim-LIT: A Simulation Framework for Image Quality Assessment in Wireless Visual Sensor Networks under Packet Loss Conditions

In this paper we present Sim-LIT, a framework for the simulation of packet loss effects on the quality of non-coded or coded still images transported over wireless sensor networks. The tool is focused on image quality assessment and it can be used to evaluate error resilience during image communications. In this first version the evaluation of block interleaving methods is provided. Sim-LIT is highly configurable, providing several options and additional tools. It may be useful to rapidly evaluate interleaving algorithms, or other techniques, or to perform extensive tests considering various image files and loss patterns. Through different simulations we demonstrate the potential of Sim-LIT as a tool for supporting research activities on the image processing and wireless sensor networks domains.

Assessing Availability in Wireless Visual Sensor Networks Based on Targets’ Perimeters Coverage

Availability in wireless visual sensor networks is a major design issue that is directly related to applications monitoring quality. For targets monitoring, visual sensors may be deployed to cover most or all of targets, and monitoring quality may be focused on how well a set of targets are being covered. However, targets may have different dimensions and it is expected that large targets may be only partially viewed by source nodes, which may affect coverage quality and lead to a state of unavailability. In this context, this article analyzes the effect of target’s size on effective coverage in wireless visual sensor networks. A new coverage metric, the Effective Target Viewing ETV, is proposed to measure monitoring quality over a set of targets, which is exploited as a fundamental parameter for availability assessment. Results show that ETV can be used as a practical coverage metric when assessing availability in wireless visual sensor networks.

Experimenting with RSSI for the perception of moving units in intelligent flexible manufacturing systems

The incorporation of autonomous wireless devices in monitoring and control supporting in industrial systems is an emerging issue which opens a wide spectrum of possibilities. Intelligent flexible manufacturing systems might require a knowledge of the time a pallet or any other approaching transport unit needs to get a flexible manufacturing cell (FMC), for early reaction to the arrival of one of these. In this paper, we evaluate RSSI as an information source to estimate the arrival time of pallets equipped with XBee wireless modules transported to and from FMCs through a conveyor belt. Obtained results show us that in indoor environments RSSI can be used in short distances with strong transmission power, being also able to determine the order of the pallets moving on the conveyor belt.

Applying Gaia and AUML for the development of multiagent-based control software for flexible manufacturing systems: addressing methodological and implementation issues

In this article, we present the development of a simple multiagent‐based system for the control of a flexible manufacturing system. We followed the stages of a methodology specially conceived for the development of agent‐based system, which is an integration of the classical methodology for agent‐oriented analysis and design Gaia, and AUML (Agent‐Unified Modeling Language). We adopted as study case the CIMUBB Laboratory at the University of Bio‐Bio, which has a flexible manufacturing system including three flexible manufacturing cells interconnected by a conveyor belt. In the analysis stage, we identified roles involved, and we design models representing roles and protocols. In the design stage, we applied Gaia agent, services, and acquaintance models from Gaia, and we complemented with AUML as the adopted methodology suggests. With the developed models, we constructed a fully functional system where each agent was built as an independent process tree. Agents communicate by passing messages through the Ethernet network with socket interfaces. Various tests executed in our laboratory scale manufacturing system show the effectiveness of our implementation. Copyright

Evaluation of block interleaving techniques for robust image communication in wireless camera sensor networks

We study block interleaving techniques for enhancing robustness against packet loss on wireless vision sensor networks. We evaluate three techniques: DSJ-AL interleaving, Turner and Peterson (TP) technique, and Torus Automorphisms (TA). Results in terms of image quality, obtained trough extensive simulations over monochromatic images, show the improvements provided by interleaving techniques in comparison with a sequential communication, with a slight favor to TA.

Protocol for Energy-Efficiency in Networked Control Systems Based on WSN

This paper proposes a new communication protocol for output-feedback control through multi-hop Wireless Sensor Network (WSN). The protocol is based on a Hop-by-Hop transport scheme and is especially devised to simultaneously fulfill two conflicting criteria: the network energy consumption and the stability/performance (in terms of H∞ norm) of the closed-loop system. The proposed protocol can be implemented by means of three heuristics, basically using distinct rules to control the maximum number of retransmissions allowed in terms of the voltage level of the batteries of the network nodes. As another contribution, a Markov jump based representation is proposed to model the packet loss in the communication channel, giving rise to a systematic procedure to determine the transition probability matrix and the Markov chain operation modes of a network with multiple information sources. The synthesis of the output-feedback controller is made in two steps (observer filter plus a state-feedback controller) for the Markov model assuming partial availability of the operation modes. The efficiency and applicability of the communication protocol is illustrated by means of a numerical experiment, based on a physical model of a coupled tanks plant. The features of each heuristic of implementation of the proposed protocol are presented in the numerical comparisons.