Carlos Miguel Tavares Calafate

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

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.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.

Emergency Services in Future Intelligent Transportation Systems Based on Vehicular Communication Networks

Over the years, we have harnessed the power of computing to improve the speed of operations and increase in productivity. Also, we have witnessed the merging of computing and telecommunications. This excellent combination of two important fields has propelled our capability even further, allowing us to communicate anytime and anywhere, improving our work flow and increasing our quality of life tremendously. The next wave of evolution we foresee is the convergence of telecommunication, computing, wireless, and transportation technologies. Once this happens, our roads and highways will be both our communications and transportation platforms, which will completely revolutionize when and how we access services and entertainment, how we communicate, commute, navigate, etc., in the coming future. This paper presents an overview of the current state-of-the-art, discusses current projects, their goals, and finally highlights how emergency services and road safety will evolve with the blending of vehicular communication networks with road transportation.

CityMob: A Mobility Model Pattern Generator for VANETs

Ad hoc networking is regarded as an adequate solution to cooperative driving between communicating cars on the road. Deploying and testing these networks, usually known as Vehicular Ad-hoc Networks (VANETs), involves a high cost in the real world, and so simulation is an useful alternative in research. One of the most critical issues in a simulation study of VANETs is the use of a mobility model which resembles, as closely as possible, the real behavior of vehicular traffic. Mobility models are crucial to obtain accurate and meaningful simulation results. In this paper we present CityMob, a mobility pattern generator for VANETs. Citymob allows researchers to easily create urban mobility scenarios, including the possibility to model car accidents. We designed and developed it targeting compatibility with the ns- 2 simulator, and we implemented three different mobility models: Simple Model (SM), Manhattan Model (MM) and Downtown Model (DM). Based on a flooding alert protocol we show that the most realistic mobility model to simulate traffic accidents is the Downtown model. We also find that, for flooding to be effective, a moderate number of vehicles is required.

Improving Selfish Node Detection in MANETs Using a Collaborative Watchdog

Mobile ad-hoc networks (MANETs) are composed of mobile nodes connected by wireless links without using any pre-existent infrastructure. MANET nodes rely on network cooperation schemes to properly work, forwarding traffic unrelated to its own use. However, in the real world, most nodes may have a selfish behavior, being unwilling to forward packets for others in order to save resources. Therefore, detecting these nodes is essential for network performance. Watchdogs are used to detect selfish nodes in computer networks. A way to reduce the detection time and to improve the accuracy of watchdogs is the collaborative approach. This paper proposes a collaborative watchdog based on contact dissemination of the detected selfish nodes. Then, we introduce an analytical model to evaluate the detection time and the cost of this collaborative approach. Numerical results show that our collaborative watchdog can dramatically reduce the overall detection time with a reduced overhead.

Realistic Radio Propagation Models (RPMs) for VANET Simulations

Deploying and testing Vehicular Ad hoc Networks (VANETs) involves high cost and intensive labor. Hence simulation is a useful alternative prior to actual implementation. Most works found in the literature employ very simplistic Radio Propagation Models (RPMs), ignoring the dramatic effects presented by buildings on radio signals. In this paper, we present three different RPMs that increase the level of realism, thereby allowing us to obtain more accurate and meaningful results. These models are: (a) the Distance Attenuation Model (DAM), (b) the Building Model (BM), and (c) the Building and Distance Attenuation Model (BDAM). We evaluated these different models and compared them with the Two-ray Ground model implemented in ns-2. We then carried out further study to evaluate the impact of varying some important parameters such as vehicle density and building size on VANET warning message dissemination. Simulation results confirmed that our proposed BDAM significantly affects the percentage of blind vehicles present and the number of received warning messages, and that our models can better reflect realistic scenarios.

Road Side Unit Deployment: A Density-Based Approach

Currently, the number of vehicles increases every year, raising the probability of having accidents. When an accident occurs, wireless technologies enable vehicles to share warning messages with other vehicles by using vehicle to vehicle (V2V) communications, and with the emergency services by using vehicle to infrastructure (V2I) communications. Regarding vehicle to infrastructure communications, Road Side Units (RSUs) act similarly to wireless LAN access points, and can provide communications with the infrastructure. Since RSUs are usually very expensive to install, authorities limit their number, especially in suburbs and areas of sparse population, making RSUs a precious resource in vehicular environments. In this paper, we propose a Density-based Road Side Unit deployment policy (D-RSU), specially designed to obtain an efficient system with the lowest possible cost to alert emergency services in case of an accident. Our approach is based on deploying RSUs using an inverse proportion to the expected density of vehicles. The obtained results show how D-RSU is able to reduce the required number of RSUs, as well as the accident notification time.

DTN Protocols for Vehicular Networks: An Application Oriented Overview

This survey provides an in-depth analysis of the different proposals for Vehicular Delay Tolerant Networks (VDTNs). We introduce the DTN architecture and classify VDTN proposals according to the type of knowledge needed to route messages. This classification also includes some Delay Tolerant Network (DTN) protocols originally designed for Opportunistic Networks to illustrate the evolution from Opportunistic DTN protocols to VDTN protocols. We also identify a set of common mechanisms that can be applied to almost all the VDTN protocols, heavily influencing their performance. Finally, we present some applications where VDTNs can be applicable and evaluate the suitability of the different proposals for each specific application. Moreover, this survey is not only limited to describing the different protocols but also focuses on the reproducibility and repeatability of experiments. With this in mind, we also review the evaluation methods used by VDTN researchers. We identify a lack of realism in most of the simulation models used by the VDTN research community, providing certain guidelines to address this issue.

OLSR vs DSR: A comparative analysis of proactive and reactive mechanisms from an energetic point of view in wireless ad hoc networks

Untethered nodes in mobile ad hoc networks strongly depend on the efficient use of their batteries. Despite the fact that devices are getting smaller and more powerful, advances in battery technology have not yet reached the stage where devices can autonomously operate for days. At the network layer, routing protocols may balance power consumption at nodes according to their routing decisions. In this paper, an in-depth performance comparison of the DSR (Dynamic Source Routing) and the OLSR (Optimized Link State Routing) is presented in terms of energy consumption. Using the ns-2 simulator an evaluation is made of how the different approaches affect the energy use of mobile devices. It was found that a reactive protocol takes advantage of its routing policy when the traffic load is low. However, at higher traffic rates, a proactive routing protocol can perform better with an appropriate refresh parameter. Also, it is demonstrated that independently of the routing protocol selected, the overhearing activity can seriously affect performance. To the best of our knowledge, this is the first simulation study addressing the power saving issue to extensively compare the DSR and OLSR protocols under a wide variety of networking scenarios.

Computer Simulations of VANETs Using Realistic City Topologies

Researchers in vehicular ad hoc networks (VANETs) commonly use simulation to test new algorithms and techniques. This is the case because of the high cost and labor involved in deploying and testing vehicles in real outdoor scenarios. However, when determining the factors that should be taken into account in these simulations, some factors such as realistic road topologies and presence of obstacles are rarely addressed. In this paper, we first evaluate the packet error rate (PER) through actual measurements in an outdoor road scenario, and deduce a close model of the PER for VANETs. Secondly, we introduce a topology-based visibility scheme such that road dimension and geometry can be accounted for, in addition to line-of-sight. We then combine these factors to determine when warning messages (i.e., messages that warn drivers of danger and hazards) are successfully received in a VANET. Through extensive simulations using different road topologies, city maps, and visibility schemes, we show these factors can impact warning message dissemination time and packet delivery rate.

DrivingStyles: A smartphone application to assess driver behavior

The DrivingStyles architecture integrates both data mining techniques and neural networks to generate a classification of driving styles by analyzing the driver behavior along each route. In particular, based on parameters such as speed, acceleration, and revolutions per minute of the engine (rpm), we have implemented a neural network based algorithm that is able to characterize the type of road on which the vehicle is moving, as well as the degree of aggressiveness of each driver. The final goal is to assist drivers at correcting the bad habits in their driving behavior, while offering helpful tips to improve fuel economy. In this work we take advantage of two key-points: the evolution of mobile terminals and the availability of a standard interface to access car data. Our DrivingStyles platform to achieve a symbiosis between smartphones and vehicles able to make the former operate as an onboard unit. Results show that neural networks were able to achieve a high degree of exactitude at classifying both road and driver types based on user traces. DrivingStyles is currently available on the Google Play Store platform for free download, and has achieved more than 1550 downloads from different countries in just a few months.