Showing papers by "Manuel P. Malumbres published in 2009"

QoS Support in MANETs: a Modular Architecture Based on the IEEE 802.11e Technology

Abstract: Providing quality-of-service (QoS) in wireless ad hoc networks is an intrinsically complex task due to node mobility, distributed channel access, and fading radio signal effects. This goal can be successfully accomplished only through the cooperation of the different protocol layers involved. In this paper we propose a novel QoS architecture that is able to support applications with the bandwidth, delay, and jitter requirements in MANET environments. The proposed architecture is modular, allowing the plugging in of different protocols, which offers great flexibility. Despite its modularity, we propose optimizations based on interactions between the media access control (MAC), routing, and admission control layers which offer important performance improvements. We validate our proposal in scenarios where different network loads, node mobility degrees, and routing algorithms are tested in order to quantify the benefits offered by our QoS proposal. In particular, we have also used real H.264/AVC video traces to simulate video sources in order to measure the quality in terms of peak signal to noise ratio of the received video, so that the benefits of applying our QoS scheme to video sources can be assessed in terms of user satisfaction (from the applications perspective).

Analyzing the behavior of acoustic link models in underwater wireless sensor networks

Abstract: In the last years, wireless sensor networks have been proposed for their deployment in underwater environments where a lot of applications like aquiculture, pollution monitoring and offshore exploration would benefit from this technology. Despite having a very similar functionality, Underwater Wireless Sensor Networks (UWSNs) exhibit several architectural differences with respect to the terrestrial ones, which are mainly due to the transmission medium characteristics (sea water) and the signal employed to transmit data (acoustic ultrasound signals). So, the design of appropriate network architecture for UWSNs is seriously hardened by the specific characteristics of the communication system. In this work we analyze several acoustic channel models for their use in underwater wireless sensor network architectures. For that purpose, we have implemented them by using the OPNET Modeler tool in order to perform an evaluation of their behavior under different network scenarios. Finally, some conclusions are drawn showing the impact on UWSN performance of different elements of channel model and particular specific environment conditions

E-LTW: An enhanced LTW encoder with sign coding and precise rate control

Abstract: Traditional embedded coding systems involve high complexity algorithms, requiring fast and expensive processors. In the last years, several authors have developed very fast and simple non-embedded wavelet encoders that are able to get reasonable good performance with reduced computing requirements. These encoders have lost the SNR scalability and precise rate control capabilities. In this paper, we propose a new non-embedded LTW codec version (E-LTW) with precise rate control method and good R/D performance due to the use of intra band neighboring context modeling for sign coding.

Underwater Wireless Networking Techniques

Abstract: Underwater sound has probably been used by marine specimens for millions of years as a communication capability among the members of a same species. It is said that in 1490, Leonardo Da Vinci wrote the following sentence: “If you cause your ship to stop and place the head of a long tube in the water and place the outer extremity to your ear, you will hear ships at a great distance from you” (Urick, 1983); being perhaps the first recorded experiments about hearing underwater sounds. In 1826 on Lake Geneva, Switzerland, the physicist Jean-Daniel Colladon, and his mathematician friend Charles-Francois Sturm, made the first recorded attempt to determine the speed of sound in water. In their experiment, the underwater bell was struck simultaneously with ignition of gunpowder on the first boat. The sound of the bell and flash from the gunpowder were observed 10-miles away on the second boat. The time between the gunpowder flash and the sound reaching the second boat was used to calculate the speed of sound in water. Colladon and Sturm were able to determine the speed of sound in water fairly accurately with this method. (Colladon, 1893). This experiment on sound propagation through water laid the foundation for underwater acoustic technology, which paved the way for the development of this technology up to our days. In 1906, Lewis Nixon invented the very first sonar-type listening device, increasing the demand of this technology during World War I to detect submarines. In 1915, the physicist Paul Langévin and the engineer Constantine Chilowski, invented the first sonar-type device for detecting submarines, called an “echo location to detect submarines,” using the piezoelectric properties of the quartz. He was too late to offer any help to the war effort; however, Langévin’s work heavily influenced future sonar designs. After using underwater sound technology for measuring the proximity to the shore and other ships, researchers soon realized that, if the sound device was pointed down at the seafloor, the depth could be accurately determined. So, new applications of sonar devices were discovered, like active depth measuring (bathymetry), seafloor shape registering, search for geological resources (i.e., oil, gas, etc.), detecting and tracking fish banks, submarine archaeology, and so forth. Although the underwater acoustic applications were mainly focused in ranging applications, exploration of seafloor and fishery by means of sonar devices, the interest in underwater multipoint communications was stressed in the 1990’s, where synoptic, spatially sampled oceanographic surveillance has provided an impetus to the transfer of networked communication technology to the underwater environment. One of the former deployments was the autonomous oceanographic surveillance network (AOSN), supported by the US Office of Naval Research (ONR) (Curtin, Bellingham, Catipovic, & Webb, 1993). It calls for a system of moorings, surface buoys, underwater sensor nodes, and autonomous underwater vehicles (AUVs) to coordinate their sampling via an acoustic telemetry network.

Mobile Ad Hoc Networks

Abstract: This chapter offers a state-of-the-art review in mobile ad hoc networks (MANETs). It first introduces the history of ad hoc networks, explaining the ad hoc network concept and referring to the main characteristics of these networks and their fields of application. It then focuses on technologies and protocols specific to ad hoc networks. Firstly, it refers to relevant proposals targeting the PHY/MAC layers. Secondly, it discusses the different routing protocol proposals for ad hoc networks according to the category they belong to. Finally, it includes an overview of the different protocols proposed for ad hoc networks at the transport layer. The chapter concludes with some remarks on future trends in these networks.