Réseaux de données en acoustique sous-marine

Cette thèse porte sur les réseaux acoustiques de données dans le contexte des installations pétrolières sous-marines. L'enjeu est de pouvoir faire communiquer différents éléments de contrôle d'une plateforme pétrolière sans utiliser des liaisons filaires, l'installation de telles liaisons étant coûteuse en temps et en argent. L'onde acoustique est donc la seule alternative possible. Les caractéristiques du milieu sous-marin et de la propagation de l'onde acoustique dans l'eau limitent les performances des systèmes de communication acoustique sous-marine. Tout d'abord, la célérité de l'onde acoustique dans l'eau est très faible par rapport à celle des ondes radio dans l'air. La seconde restriction liée à ce milieu vient du fait que les ressources fréquentielles sont sévèrement limitées. L'objectif de ce travail est d'optimiser l'utilisation de ces ressources tout en augmentant le débit reçu et en réduisant le délai de transmission. Pour réaliser cet objectif, nous avons structuré notre travail en trois volets:le premier volet concerne la proposition des mécanismes MAC adaptés au milieu sous-marin; le deuxième volet concerne le développement de nouvelles techniques de transmission adaptées au contexte des communications acoustiques sous-marines; et enfin le troisième volet concerne l'optimisation conjointe de ces deux couches en proposant une approche Cross Layer. Notre protocole MAC est basé sur le mécanisme CSMA/CA. Le principe de notre système de transmission est basé sur les techniques CDMA avec une transmission sur plusieurs antennes. La troisième étape de ce travail est de fusionner ces deux parties indépendantes pour proposer un protocole Cross Layer.This thesis deals with acoustic data networks in the context of oil offshore platforms. The problem involves setting up a set of offshore platform control stations that are capable of communicating between them in a wireless way. Since cable installations is a costly process both in terms of time and money, the solution using acoustic wave is the only possible and efficient alternative. The underwater channel and the acoustic wave propagation properties limit acoustic communication system performance. The propagation speed of the acoustic wave under water is very low compared to the propagation speed of the electromagnetic wave. The second underwater channel particularity is that the frequency band resources are severely limited. The aim of this work is to optimize use of resources by increasing network throughput and reducing transmission delay. To achieve this purpose, we have divided this work into three points: The first point is concerned with the proposition of MAC mechanisms adapted to underwater context, the second point disucusses the proposition of transmission techniques adapted for underwater acoustic communications, and the third point deals with the optimization of the two layers and the proposition of a Cross Layer approach. Our proposition of a MAC protocol is based on CSMA/CA mechanism. The transmission system we have proposed is based on Code Division Multiple Access (CDMA) techniques with several antennas. The third step of this work is to combine these two parts in order to propose a Cross Layer approach which optimizes the two layers.LORIENT-BU (561212106) / SudocBREST-Télécom Bretagne (290192306) / SudocSudocFranceF

Transmit diversity for CDMA with constraint of discretion

International audienceTransmit diversity for CDMA with constraint of discretio

Analysis of MAC protocols for Underwater Acoustic Data Networks

International audienceThis paper presents a state of art of existing Underwater Acoustic Networks. We study specifically the Media Access Control (MAC) Protocol design of research work done in this field. A comparison of different protocols is presented according to several criteria: propagation delay, node connectivity and energy consumption. This comparison allows us to present some ideas for a new design of a MAC Underwater Acoustic protocol

Distributed MAC Protocols for Underwater Acoustic Data Networks

International audienceIn this paper, we consider MAC (media access control) protocols appropriate to the underwater acoustic networks. First, we consider a media access method based on the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocol used in the wireless local area networks IEEE 802.11 (WiFi). In the underwater acoustic channel, the acoustic wave propagates very slowly with regard to the electromagnetic wave (about 1500 m s ). Therefore the propagation delay is significant and thus collisions present a high cost considering the delay of transmission and the available throughput. To avoid this problem, we consider a second protocol in which we integrate a WAIT command [1]. Finally we integrate to our proposition a power control mechanism in order to increase network performance (delay, throughput). The performance evaluation of the three propositions has been done in terms of available throughput of the underwater sensors, delay of transmission and collision probability. The proposed simulation system model is detailed

Power and distance based MAC algorithms for underwater acoustic networks

International audienceIn this paper, we study MAC (Media Access Control) protocols for underwater acoustic networks. Our starting point is the protocol based on the CSMA/CA method. We propose to modify the CSMA/CA in order to increase the protocol performance. The first proposition requires a local knowledge about distance between nodes. If a node knows the distance separating it to the destination, it can adapt the timeout parameter (the time that a node waits for before repeating its request of transmitting) to this distance. In wireless networks the adaptation of this parameter has no interesting influence while in the case of underwater communication, propagation delay is important and so adapting the timeout parameter allows interesting gains in delay and throughput. We propose then to control transmission power in order to decrease probability of collision and energy consumption. Comparison of protocols performance is done in term of available throughput of nodes and delay of transmission. The simulation system model is detaile

A cross layer approach with CSMA/CA based protocol and CDMA transmission for underwater acoustic networks

International audienceIn this paper, we propose a cross layer design which combines the PHYsical and the MAC layers for a distributed wireless underwater acoustic networks. The PHYsical layer is based on a CDMA transmission as used in UMTS systems, reception is done using a RAKE receiver. The MAC layer is a based on the CSMA/CA protocol. As we work in the case of underwater acoustic networks, the propagation delay is much more significant compared to radio channel. Therefore, the use of RTS/CTS used in the CSMA/CA protocol induces an increase in delay. The use of CSMA techniques allows to several nodes to transmit simultaneously through the common channel and without using control sequences RTS/CTS to reserve the medium. We show in this paper that our proposition solves the problem of collision present in the case of CSMA/CA. The comparison between our cross layer approach and the CSMA/CA is done in term of available throughput of nodes and average delay of transmission