Francis Lepage

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.

Multi-channel clustering algorithm for improving performance of large-scale wireless multi-sink sensor networks

This paper presents a simple and distributed clustering algorithm suitable for large-scale wireless sensor networks (WSNs) consisting of several thousands of sensor nodes and few sink nodes. A two-tiered hierarchical architecture is used to increase scalability and ensure performances and durability of such a system: Level 1 called sensor network is partitioned into several equilibrate clusters with one leader or sink by cluster; Level 2 also called sink network is composed by N sink nodes placed in planned manner into monitored region and is connected through IEEE 802.11 radio interfaces. A multi-channel system is used to create a cellular structure by assigning one frequency channel per cluster. We use simulation technique to evaluate and compare the impact of two distributed schemes (a single channel one and a multi-channel one) on network capacity like traffic load, energy consumption, medium access delay, end-to-end delay and data delivery ratio.

Quality control in a flexible manufacturing cell

Summary This paper presents a quality control loop architecture of a flexible manufacturing cell. Re cell is considered as an autonomous system which produces pans and controls their quality and which manages its own equipement and adapts its behaviour according to the most recent information. The quality control in the cell is based on two principles concepts: - management of all technical and quality information in the cell information system. - distributed control of the cell on several levels to perform correction as Past as possible. An application using a MAP local ma network and S Q L server realized in the C.R.A.Y. is described.

From Standalone N.C. Machine Tools to Evolutive Flexible Manufacturing Cell A Feasible Solution for Small Industries: The C.U.C.N. Project

Most of the french small industries are equipped with standalone N.C. Machine tools. Industrials are looking for a further step in higher automated production, but with a smooth and cheap evolution, using their existing machine tools. To reach this goal, the C.U.C.N. Research project includes the following fields: - development of specific interfaces to ensure easy connexion between N.C. and computer, through a reliable local area network, - integration and control of loading and unloading robot, using L.M. Language, - integration of a N.C. measuring machine to follow the geometrical dimension evolution of the parts and calculate part program corrections, in order to keep production quality, - development of software for control and supervision of the whole cell. This paper describes the main caracteristics and possibilities of the experimental cell which includes a lathe, a machining center, a measuring machine, a gantry robot and a mini computer.

Cluster-based multi-channel system for improving performance of large-scale wireless multi-sink sensor networks

This paper presents a simple and distributed clustering algorithm suitable for large-scale wireless sensor networks (WSNs) consisting of several thousands of sensor nodes and few sink nodes. A two-tiered hierarchical architecture is used to increase scalability and ensure performances and durability of such a system: Level 1 called sensor network is partitioned into several equilibrate clusters with one leader or sink by cluster; Level 2 also called sink network is composed by N sinks nodes placed in planned manner into monitored region and is connected through IEEE 802.11 radio interfaces. A multi-channel system is used to create a cellular structure by assigning one frequency channel per cluster. We use simulation technique to evaluate and compare the impact of two distributed schemes (a single channel one and a multi-channel one) on network capacity like traffic load, energy consumption, medium access delay, end-to-end delay and data delivery ratio.

Distributed Multimedia Modeling in an MMS Context

Abstract Distributed multimedia applications would be a useful tool in the manufacturing industry. They are typically time-based applications which impose several time related constraints on communication systems. Quality of Service (QoS) parameters are necessary to describe the requirements to transfer multimedia information in communication systems. The international standard Manufacturing Message Specification (MMS) is an application layer protocol which specifies services for the distributed manufacturing applications. It enables communications between heterogeneous devices, but is not suitable for multimedia applications because it does not present QoS parameters to its objects and services. This paper proposes an extension of MMS for integrating multimedia functions. The goal is to define an MMS multimedia companion standard. Like the VMD which models manufacturing devices for MMS communication, a Virtual Communication Support (VCS) is proposed to virtualize a communication system in an MMS environment. Potential uses of VCS are also discussed.

Ensuring Performances of Large Scale Wireless Sensor Networks with Multiple Sinks and Multiple Channels

This paper presents a simple and distributed clustering algorithm suitable for large-scale wireless sensor networks (LSWSNs) consisting of several thousands of nodes. A two-tiered hierarchical architecture is used to increase scalability and ensure performances and durability of such a system: Level 1 called sensor network is partitioned into several equilibrate clusters with one leader or sink by cluster; Level 2 also called sink network is composed by N sink nodes placed in planned manner into monitored region and is connected through IEEE 802.11 radio interfaces. A multi-channel system is used to create a cellular structure by assigning one frequency channel per cluster. We use simulation technique to evaluate and compare the impact of two distributed schemes (a single channel one and a multi-channel one) on network capacities like traffic load, energy consumption, medium access delay, end-to-end delay and data delivery ratio.