Showing papers by "Juan-Carlos Cano published in 2011"

A survey and comparative study of simulators for vehicular ad hoc networks (VANETs)

Abstract: Wireless communication technologies have now greatly impact our daily lives. From indoor wireless LANs to outdoor cellular mobile networks, wireless technologies have benefited billions of users around the globe. The era of vehicular ad hoc networks (VANETs) is now evolving, gaining attention and momentum. Researchers and developers have built VANET simulation software to allow the study and evaluation of various media access, routing, and emergency warning protocols. VANET simulation is fundamentally different from MANETs (mobile ad hoc networks) simulation because in VANETs, vehicular environment imposes new issues and requirements, such as constrained road topology, multi-path fading and roadside obstacles, traffic flow models, trip models, varying vehicular speed and mobility, traffic lights, traffic congestion, drivers' behavior, etc. Currently, there are VANET mobility generators, network simulators, and VANET simulators. This paper presents a comprehensive study and comparisons of the various publicly available VANET simulation software and their components. In particular, we contrast their software characteristics, graphical user interface (GUI), popularity, ease of use, input requirements, output visualization capability, accuracy of simulation, etc. Finally, while each of the studied simulators provides a good simulation environment for VANETs, refinements and further contributions are needed before they can be widely used by the research community. Copyright © 2009 John Wiley & Sons, Ltd.

Providing accident detection in vehicular networks through OBD-II devices and Android-based smartphones

Abstract: The increasing activity in the Intelligent Transportation Systems (ITS) area faces a strong limitation: the slow pace at which the automotive industry is making cars "smarter". On the contrary, the smartphone industry is advancing quickly. Existing smartphones are endowed with multiple wireless interfaces and high computational power, being able to perform a wide variety of tasks. By combining smartphones with existing vehicles through an appropriate interface we are able to move closer to the smart vehicle paradigm, offering the user new functionalities and services when driving. In this paper we propose an Android-based application that monitors the vehicle through an On Board Diagnostics (OBD-II) interface, being able to detect accidents. Our proposed application estimates the G force experienced by the passengers in case of a frontal collision, which is used together with airbag triggers to detect accidents. The application reacts to positive detection by sending details about the accident through either e-mail or SMS to pre-defined destinations, immediately followed by an automatic phone call to the emergency services. Experimental results using a real vehicle show that the application is able to react to accident events in less than 3 seconds, a very low time, validating the feasibility of smartphone based solutions for improving safety on the road.

HOP: achieving efficient anonymity in MANETs by combining HIP, OLSR, and pseudonyms

Abstract: Offering secure and anonymous communications in mobile ad hoc networking environments is essential to achieve confidence and privacy, thus promoting widespread adoption of this kind of networks. In addition, some minimum performance levels must be achieved for any solution to be practical and become widely adopted. In this paper, we propose and implement HOP, a novel solution based on cryptographic Host Identity Protocol (HIP) that offers security and user-level anonymity in MANET environments while maintaining good performance levels. In particular, we introduce enhancements to the authentication process to achieve Host Identity Tag (HIT) relationship anonymity, along with source/destination HIT anonymity when combined with multihoming. Afterward we detail how we integrate our improved version of HIP with the OLSR routing protocol to achieve efficient support for pseudonyms. We implemented our proposal in an experimental testbed, and the results obtained show that performance levels achieved are quite good, and that the integration with OLSR is achieved with a low overhead.

Prototyping an automatic notification scheme for traffic accidents in vehicular networks

Abstract: The new communication technologies integrated into the automotive sector offer an opportunity for better assistance to people injured in traffic accidents, reducing the response time of emergency services, and increasing the information they have about the incident. Determining more accurately the human and material resources required for each particular accident could significantly reduce the number of victims. The proposed system requires each vehicle to be endowed with an On-Board Unit responsible for detecting and reporting accident situations to an external Control unit that estimates its severity, allocating the necessary resources for its assistance. The development of a prototype based on off-the-shelf devices shows that this system could reduce notably the time needed to deploy the emergency services after an accident takes place.

A Street Broadcast Reduction Scheme (SBR) to Mitigate the Broadcast Storm Problem in VANETs

Abstract: In urban vehicular wireless environments, several vehicles can send warning messages and so every vehicle within the transmission range will receive the broadcast transmission, possibly rebroadcasting these messages to other vehicles. This increases the number of vehicles receiving the traffic warning messages. Hence, redundancy, contention, and packet collisions due to simultaneous forwarding (usually known as the broadcast storm problem), can occur. In the past, several approaches have been proposed to solve the broadcast storm problem in wireless networks such as Mobile ad hoc Networks MANETs. In this paper, we present Street Broadcast Reduction SBR, a novel scheme that mitigates the broadcast storm problem in VANETs. SBR also reduces the warning message notification time and increases the number of vehicles that are informed about the alert.

Evaluation of a technology-aware vertical handover algorithm based on the IEEE 802.21 standard

Abstract: Nowadays, due to the ubiquity of wireless technologies, users demand continuous connectivity guaranteeing the Quality of Service (QoS) required for their communications. To fulfill those requirements, seamless Vertical Handover (VHO) is performed in order to maintain the connectivity among different wireless technologies while the user equipment moves across different coverage areas. In this work, we present a set of experiments to evaluate the vertical handover performance when relying on the IEEE 802.21 standard in scenarios where Wi-Fi, WiMAX and UMTS technologies are available. Experimental results show that a technology-aware vertical handover mechanism is able to achieve an adequate performance when traffic congestion is low.

Analysis of the Most Representative Factors Affecting Warning Message Dissemination in VANETs under Real Roadmaps

Abstract: In recent years, new architectures and technologies have been proposed for Vehicular ad hoc networks (VANETs).However, the experiments to validate these proposals tend to overlook the most important and representative factors. Moreover, the scenarios simulated tend to be very simplistic (highways or Manhattan-based layouts), which could seriously affect the validity of the obtained results. In this paper, we present a statistical analysis based on the2k factorial methodology to determine the most representative factors affecting traffic safety applications under real roadmaps. Our purpose is to determine which are the key factors affecting Warning Message Dissemination (WMD) in order to concentrate on such parameters, thus reducing the amount of simulation time required. Simulation results show that the key factors affecting warning messages delivery are the density of vehicles, and the roadmap used. Based on this statistical analysis, we consider that VANET researchers must evaluate the benefits of their proposals using different vehicle densities and city scenarios.

Performance Trade-Offs of a IEEE 802.21-Based Vertical Handover Decision Algorithm under Different Network Conditions

Abstract: Wireless technologies have been widely deployed in the last decade making users demand for continuous connectivity. Users not only demand being attached to a network, but possibly to the one with the highest performance, or at least to a network able to fulfill their requirements. To choose the best network among different candidates, the IEEE 802.21 standard has been developed. In this paper we aim at demonstrating the viability of performing Vertical Handover (VHO) processes based on the IEEE 802.21 protocol. To do so, we have evaluated a VHO strategy which considers network availability and maximum data rate in order to choose the best network candidate among the Wi-Fi, the WiMAX, and the UMTS. Moreover, throughout a set of experiments, we have also evaluated the maximum performance of the available networks.

Proceedings of the 6th ACM workshop on Performance monitoring and measurement of heterogeneous wireless and wired networks

Abstract: We would like to welcome you to the Seventh ACM International Workshop on Performance Monitoring, Measurement, and Evaluation of Heterogeneous Wireless and Wired Networks (PM2HW2N'12), held in conjunction with the 15th ACM International Conference on Modeling, Analysis and Simulation of Wireless and Mobile Systems (MSWiM'12), on October 21-25, 2012 in Paphos, Cyprus. Following the success of our previous workshops, PM2HW2N'12 aims to provide researchers from academia and industry with a forum to share and exchange their experiences, discuss challenges, and report state-of-the-art and in-progress research on all aspects of monitoring and measurement of heterogeneous wireless and wired networks with special emphasis on performance modeling, evaluation and analysis. We have received several papers related to the above research issues in response to our call for papers. All of the papers submitted have been peer-reviewed by at least two referees from the Technical Program Committee, with most of the papers being reviewed by three referees. Based on the outcome of the reviews, seventeen papers were selected for publication in this ACM proceedings and for presentation at the workshop.

Studying the feasibility of IEEE 802.15.4-Based WSNs for gas and fire tracking applications through simulation

Abstract: Wireless Sensor Networks (WSNs) have proliferated significantly in recent years. Nowadays they are used in many fields, such as military, environmental and industrial. Reliability and low latency are desirable characteristics of many WSN applications. In particular, time-critical WSN applications must be able to act according to the observed changes in the environment as quickly as possible, assuring that the information collected by the sensor nodes is correct. In these applications the response time is a critical factor. In this paper, we focus on WSN monitoring applications for both indoor and outdoor environments. We propose a near real-time monitoring system based on binary detection sensor that offers delay bounded tracking of events, such as gas and fire. The performance of gas and fire tracking applications is evaluated using the IEEE 802.15.4 technology and a routing scheme for WSNs that relies on sink announcements for route discovery. The proposed routing protocol is tuned to introduce the lowest possible end-to-end delay to data packet delivery, by reducing control traffic to a minimum. To evaluate the performance, we develop both gas and fire propagation models for a framework that allows simulating emergency events, thus allowing us to determine the degree of accuracy achieved in the monitoring process.

PAWDS: A Roadmap Profile-Driven Adaptive System for Alert Dissemination in VANETs

Abstract: In traffic safety applications for Vehicular Ad hoc Networks (VANETs), warning messages have to be disseminated whenever a dangerous situation occurs to alert nearby vehicles. Using inefficient broadcast schemes may lead to ineffective dissemination of warning messages causing broadcast storm problems. In the past, several approaches have been proposed to reduce the so called broadcast storm in multi-hop wireless networks, but none of them is adapted to the features of the propagation scenario. In this paper, we present the Profile-driven Adaptive Warning Dissemination Scheme (PAWDS) to improve the warning message dissemination process. With respect to previous proposals, our PAWDS scheme uses an adaptive technique based on tuning the operation of the dissemination scheme according to the characteristics of the street area where the vehicles are moving. Our algorithm reported a noticeable improvement in the performance of alert dissemination processes in simulated scenarios based on real city maps.

Using roadmap profiling to enhance the warning message dissemination in vehicular environments

Abstract: In recent years, new applications, architectures and technologies have been proposed for Vehicular ad hoc networks (VANETs). Regarding traffic safety applications for VANETs, warning messages have to be quickly disseminated in order to reduce the required dissemination time and to increase the number of vehicles receiving the traffic warning information. In the past, several approaches have been proposed to improve the alert dissemination process in multi-hop wireless networks, but none of them is adapted to the propagation features of the scenario. In this paper, we present an adaptive algorithm designed to improve the warning message dissemination process. With respect to previous proposals, our proposed scheme uses a mapping technique based on adapting the dissemination strategy according to the characteristics of the street area where the vehicles are moving. Our algorithm reported a noticeable improvement in the performance of alert dissemination processes in simulated scenarios based on real city maps.

Assessing the best strategy to improve the stability of scalable video transmission in MANETs

Abstract: Mobile Ad Hoc Networks (MANETs) have been an important research topic for the last years, playing a crucial role within the fast growing sector of mobile communications. At the same time, video applications over mobile devices are becoming widely used by nowadays mobile clients, where the quality in the transmission of such contents will determine the success of these applications in the future. Therefore, it is mandatory to find the best strategies to guarantee a good Quality of Service (QoS) to the end-user. In this work we present a set of novel strategies to improve the performance of video transmission over MANETs. These new strategies are based on distributed admission control protocols which has proved to be helpful at achieving an efficient video transmission system. Experimental results show that, when adopting the new strategies to determine the optimal number of layers to transmit, we can achieve better results compared to other existent approaches in terms of idle time periods, fairness and delay.

Efficient routing in large sensor grids supporting mobile drains

Abstract: Different applications for Wireless Sensor Networks (WSN), such as intruder detection and pursuit scenarios, require the support for mobility. In this paper we propose the novel Mobile-drain Routing for Large Grids (MRLG) algorithm, which is intended to support drain mobility in WSNs in an efficient manner. MRLG allows reducing the routing load by relying on local route recovery processes, which provides significant efficiency in scenarios with a large number of sensors. Preliminary experimental results show that, when compared to typical proactive routing strategies based on drain announcements, the MRLG algorithm allows to significantly boost performance in terms of packet delivery ratio, end-toend delay, and routing overhead.

A methodology to evaluate video streaming performance in 802.11e based MANETs

Abstract: Video delivery in mobile ad-hoc networks (MANETs) is an exciting and challenging research field. In the past, most works addressing this issue have resorted to simulation due to the complexity of deploying QoS-enabled testbeds and retrieving video quality indexes in such environments. In this paper we introduce a methodology that allows testing the effectiveness of video codecs in ad-hoc networks. Our methodology relies on a well-defined video quality evaluation framework that is able to combine different video codecs and transmission environments. In particular, our evaluation procedures encompass a preliminary quality assessment, which relies on a point-to-point wireless channel, to establish the general behavior of a video codec under lossy channel conditions, along with tests in static and mobile ad-hoc network environments to determine the impact of factors such as congestion, hop count, and mobility on video quality. To validate our methodology we compare the H.264/AVC and the MPEG-4/ASP video codecs, showing that, in general, the former outperforms the later in terms of video quality, although, for very high loss rates, the differences between both become minimal. Additionally, we show that the number of hops between video transmitter and receiver is a decisive factor affecting performance in the presence of background traffic. Moreover, in mobile scenarios, we find that the impact of congestion and routing delay affects video streaming quality in different manners, being congestion mainly responsible for random losses, while routing delay is usually associated with large loss burst patterns.

Distributed admission control in 802.11e-based MANETs: From theory to practice

Abstract: Providing Quality of Service (QoS) in wireless ad-hoc networks is an extremely complex task due to issues such as mobility, channel contention, and interference. Over the past years, several algorithms have been presented with the aim of providing QoS support in these environments; specifically, a lot of work has been done in the creation of a reliable admission control mechanism since it has been proved to be a fundamental element for QoS support in ad-hoc networks. In this paper we present a real implementation of DACME, a distributed admission control system for mobile ad-hoc networks, and we test its effectiveness in an IEEE 802.11e enabled testbed. Experimental results show that the solution developed is able to achieve good QoS levels, offering sustained bandwidth and bounded delay. Also, since DACME operates on an end-to-end basis, no restrictions are imposed on intermediate nodes.

Design, implementation, and optimization of a Raptor-based content delivery protocol

Abstract: When attempting to deliver contents over wireless networks in an efficient manner, the different protocols involved must deal with several sources of loss such as congestion and channel errors, which can prevent an effective message reception at the destination. Therefore, content delivery protocols must deal with these problems in the most appropriate way. In this paper we focus on the design, implementation, and optimization of RCDP, a content delivery protocol for wireless network environments based on Raptor codes. We propose different architectural and design alternatives in order to find the solution that achieves the best trade-off between throughput achieved and resource requirements under both lossy and lossless conditions. Experimental results based on a real implementation of RCDP show that parallelization strategies, together with other optimizations, are able to significantly boost performance.

Design and implementation of a training tool simulator as an educational resource in Digital Systems Fundamentals

Abstract: In introductory courses on Digital System Fundamentals, it seems difficult to deal with all the circuits presented in the classroom, from a practical perspective. In order to reinforce the learning outcomes of the course and, based on the commercial trainer tool DET 2020, this paper describes the design and implementation of a simulation tool that resembles the commercial training tool, and its use as educational resource in a first-year course in Computer Engineering. We present the educational possibilities of this powerful tool, both from the student and the instructor perspective, and we discuss the results of the students' assessment about the simulator.

Raptor-based reliable unicast content delivery in wireless network environments

Abstract: Delivering contents over wireless networks can be a challenging task due to the intrinsic limitations of these environments. In this paper we propose RCDP, a solution which adopts an application layer FEC scheme based on Raptor codes to avoid retransmissions, optimizing content delivery for the unicast case. The proposed solution relies on end-to-end bandwidth estimations to perform rate control, achieving high throughput levels in lossy wireless environments. We have designed and implemented RCDP for the GNU/Linux platform to validate our approach under different channel conditions, varying packet loss ratio, end-to-end delay, and channel capacity. Experimental results show that the proposed solution is very efficient when facing high loss ratios and end-to-end delays, allowing for an efficient usage of channel resources in wireless scenarios.