Luca Bedogni

Group communication on highways

Nowadays, most of the applications proposed for Vehicular Ad Hoc Networks (VANETs) rely on geocasting, i.e. on the possibility to identify the end-points of the communication through their geographic coordinates instead of their network addresses. At the same time, each vehicular application has its own set of Quality-of-Service (QoS) requirements which must be guaranteed by the underlying dissemination protocol. This has lead to a proliferation of geocast protocols proposed in the literature of VANETs, usually based on reactive or proactive approaches. However, most of these solutions are tailored for a specific application (e.g. active-safety applications), and thus might not be suitable for generic deployments of VANETs. In this paper, we propose a Dynamic Backbone Assisted (DBA) MAC protocol as a general solution to support geocast communication on highway scenarios for different classes of vehicular applications. DBA-MAC combines the benefits of proactive and reactive schemes through a cross-layer architecture which includes: (i) a novel distributed clustering algorithm and (ii) a fast information dissemination mechanism. First, DBA-MAC creates and maintains a virtual backbone of vehicles inside the highway scenario. Then, it provides fast dissemination of geocast messages through a combination of contention-free and contention-based forwarding mechanisms at the link layer. We provide a complete and exhaustive evaluation of the DBA-MAC scheme under different application requirements and network load conditions. We propose three metrics for the selection of backbone members which provide different characteristics in terms of delivery delay and ratio, and we analyze their performance with both analytical models and simulation studies. Then, we evaluate the performance of DBA-MAC compared to traditional geocast schemes for three classes of vehicular applications: active-safety applications, traffic-information applications, multimedia streaming (audio/video) applications. The simulation results confirm that DBA-MAC is able to greatly reduce the delivery delay for active-safety applications, and to adequately meet the requirements of multimedia applications for VANETs.

By train or by car? Detecting the user's motion type through smartphone sensors data

Nowadays, the increasing popularity of smartphone devices equipped with multiple sensors (e.g. accelerometer, gyroscope, etc) have opened several possibilities to the deployment of novel and exciting context-aware mobile applications. In this paper, we exploit one of this possibility, by investigating how to detect the user motion type through sensors data collected by a smartphone. Our study combines experimental and analytical contributions, and it is structured in three parts. First, we collected experimental data that demonstrate the existence of specific sensors data patterns associated to each motion type, and we propose methods for data analysis and features extraction. Second, we compare the performance of different supervised algorithms for motion type classification, and we demonstrate that jointly utilizing the multiple sensor inputs of a smartphone (i.e. the accelerometer and the gyroscope) can significantly improve the accuracy of the classifiers. At the same time, we analyze the impact of sampling parameters (e.g. the sampling rate) on the system performance, and the corresponding trade-off between classification accuracy and energy consumption of the device. Third, we integrate the motion type recognition algorithm into an Android application, that allows to associate a specific smartphone configuration to each detected motion type, and to provide this information at system-level to other context-aware Android applications. Experimental results demonstrate the ability of our application in detecting the users motion type with high accuracy, and in mitigating the classification errors caused by random data fluctuations.

Self-organizing aerial mesh networks for emergency communication

Guaranteeing network connectivity in post-disaster scenarios is challenging yet crucial to save human lives and to coordinate the operations of first responders. In this paper, we investigate the utilization of low-altitude aerial mesh networks composed by Small Unmanned Aerial Vehicles (SUAVs) in order to re-enstablish connectivity among isolated end-user (EU) devices located on the ground. Aerial ad-hoc networks provide the advantage to be deployable also on critical scenarios where terrestrial mobile devices might not operate, however their implementation is challenging from the point of view of mobility management and of coverage lifetime. In this paper, we address both these issues with three novel research contributions. First, we propose a distributed mobility algorithm, based on the virtual spring model, through which the SUAV-based mesh node-called also Repairing Units (RUs) in this study- can self-organize into a mesh structure by guaranteeing Quality of Service (QoS) over the aerial link, and connecting the maximum number of EU devices. Second, we evaluate our scheme on a realistic 3D environment with buildings, and we demonstrate the effectiveness of the aerial deployment compared to a terrestrial one, in terms of coverage and wireless link reliability. Third, we address the problem of energy lifetime, and we propose a distributed charging scheduling scheme, through which a persistent coverage of RUs can be guaranteed over the emergency scenario.

An interoperable architecture for mobile smart services over the internet of energy

The Internet of Energy (IoE) for Electric Mobility is an European research project that aims at deploying a communication infrastructure to facilitate and support the operations of Electric Vehicles (EVs). In this paper, we present three research contributions of IoE. First, we describe a software architecture to support the deployment of mobile and smart services over an Electric Mobility (EM) scenario. The proposed architecture relies on an ontology-based data representation, on a shared repository of information (Service Information Broker), and on software modules (called Knowledge Processors -KPs) for standardized data access/management. As a result, information sharing among the different stakeholders of the EM scenario (i.e. EVs, EVSEs, City Services, etc) is enabled, and the interoperability of smart services offered by heterogeneous providers is guaranteed by the common ontology. Second, we rely on the proposed architecture to develop a remote charging reservation system, that runs on top of mobile smarthphones, and allows drivers to monitor the current state-of-charge of their EV, and to reserve a charging slot at a specific EVSE. Finally, we validate our architecture through a benchmark framework, that supports the embedding of mobile EV applications and of real KPs into a simulated vehicular scenario, including realistic traffic, wireless communication and battery models. Evaluation results confirm the scalability of our architecture, and the ability to support EVs charging operations on a large-scale scenario (i.e. the downtown of Bologna).

Internet of things: a process calculus approach

This paper presents a process calculus specifically designed to model systems based on the Internet of Things paradigm. We define a formal syntax and semantics for the calculus, and show how it can be used to reason about relevant examples. We also define two notions of bisimilarity, one capturing the behavior seen by the end user of the system, and one allowing compositional reasoning.

Smart meters with TV gray spaces connectivity: A feasibility study for two reference network topologies

With an increasing demand for monitoring energy consumption at granularity levels down to single household appliances, it is necessary to develop new means to collect sensor measurements in a robust and cost-efficient manner. The smart grid paradigm foresees using wireless links for data transfer, albeit no dedicated spectrum bands have been designated for this purpose. In this paper we study the feasibility of opportunistic spectrum access for smart grids, and focus on underlay spectrum sharing over occupied TV channels. These frequency bands, which are commonly denoted as TV gray spaces, provide superior propagation characteristics, but are locally used by high-power (mostly DTV) broadcasting transmitters. For selected reference geometries of intra-meter and meter-to-operator communications, we study the smart meter performance (in terms of achievable throughput and transmission range), and the necessary power limits. We compare our results from a small-scale measurement campaigns against existing wireless technologies for low-power communications in other adjacent bands. Our results show that wall shielding and fading in indoor to outdoor propagation channels sufficiently protects the primary system from the interference introduced by gray space meter-to-meter communications, but that the required transmit powers to send operations data from indoor meters to outdoor collection point severely limit the applicability of TV gray spaces for such network topologies.

An Integrated Simulation Framework to Model Electric Vehicle Operations and Services

At present, battery-charging operations constitute one of the most critical obstacles toward a large-scale uptake of electric mobility (EM), due to performance issues and implementation complexities. Although several solutions based on the utilization of information and communication technologies and on mobile applications have been investigated to assist electric vehicle (EV) drivers and to coordinate charging operations, there is still the problem of how to evaluate and validate such solutions on realistic scenarios, due to the lack of accurate simulators integrating vehicular mobility, wireless communication, and battery charging/discharging models. In this paper, we attempt to fill this gap by proposing a novel EV simulation platform that can assist in the predeployment of charging infrastructures and services on realistic large-scale EM scenarios. The simulation platform, which is realized within the ARTEMIS EU project “Internet of Energy for Electric Mobility,” supports two utilization modes, i.e., evaluation of EM scenarios and immersive emulation of EM-related mobile applications, due to a semantic architecture through which virtual and real components can be integrated in a seamless way. We provide three major contributions with respect to the state of the art. First, we extend the existing cosimulation platform composed of SUMO (a vehicular traffic simulator) and OMNET++ (a network simulator) with realistic models of EVs, electric vehicle supply equipment, and ontology-based communication protocols that enable the deployment of city-wide mobile services (e.g., charging reservation). Second, we validate the battery model against the consumptions data of target EVs, and we evaluate the operations of EVs on a large-scale scenario (the city of Bologna, Italy), by analyzing the effectiveness of the charging reservation process and the resulting impact to the smart grid. Finally, we introduce the Mobile Application Zoo, which is a sandbox through which EM-related mobile applications can be seamlessly integrated within the simulation platform to be validated on virtual environments before their deployment on real scenarios, and we describe the implementation of an Android application for battery monitoring and charging reservation.

STEM-mesh: Self-organizing mobile cognitive radio network for disaster recovery operations

In this paper, we address the problem of re-establishing the network connectivity in post-disaster scenarios, where the original wireless infrastructure has been partitioned into multiple network fragments (called islands), operating on different frequencies. To this purpose, we propose the utilization of swarms of dedicated repairing units, called Stem-Nodes (SNs). SNs are provided with Cognitive Radio (CR) and self-positioning capabilities, in order to offer maximum reconfigurability in terms of mobility and wireless technologies supported. Moreover, swarms of SNs can self-organize into STEM-Mesh structure, that works as a dynamic backbone to connect heterogeneous islands using different technologies (e.g. Wi-Fi, Wi-MAX, etc). In this paper, we present three contributions pertaining to STEM-Mesh: (i) we describe a distributed motion control scheme (based on virtual springs approach) that enables SNs to self-organize into dynamic STEM-Mesh structures, (ii) we introduce a discovery scheme, through which SNs can explore the scenario in both spatial and frequency domains, and possibly connect the islands to the STEM-Mesh backbone and (iii) we validate the correctness of the proposed scheme, by verifying the optimal placements of the SNs composing the STEM-Mesh on a simplified scenario (e.g. chain topology). Finally, we evaluate through Omnet++ simulations the ability of STEM-Mesh to maximally re-establish connectivity on partitioned network scenarios.

Machine-to-Machine Communication over TV White Spaces for Smart Metering Applications

Machine-to-Machine communications is envisioned to become one of the fundamental pillars of the future Internet of Things paradigm, enabling platoons of devices to be seamlessly connected and to cooperate over smart spaces. Among the possible application scenarios, smart metering represents an already existing technology that might take benefit from the capability of autonomous configuration and setup of M2M networks. At present, smart meters communicate over the 2G/3G network, however the utilization of the cellular technology poses several problems, such as low coverage and spectrum shortage over dense areas. To overcome these issues, in this paper we investigate the application of cognitive radio principles over TV White Spaces to M2M communication for the smart metering scenario. Following the recent regulations of FCC and Ofcom, that foresees the presence of a spectrum database for TV white spaces detection, we study the trade-off between protection of licensees and energy consumption in a cluster of smart meters. We provide three novel research contributions: (i) an analytical model to estimate the lifetime of a cluster of smart meters; (ii) centralized and distributed algorithms to determine the schedule operations of Master/Slave devices foreseen by the spectrum regulations; (iii) performance evaluation of the proposed framework through extensive Omnet++ simulations.

The Bologna Ringway Dataset: Improving Road Network Conversion in SUMO and Validating Urban Mobility via Navigation Services

The current lack of reference datasets of road traffic mobility for network simulation jeopardizes the reliability and reproducibility of vehicular networking research. We contribute to the ongoing effort to develop dependable and publicly available mobility traces through the following: (1) implementing an original version of the Simulation of Urban Mobility (SUMO) road network conversion tool that allows importing OpenStreetMap (OSM) data in a neat automated fashion; (2) generating an original dataset of road traffic in Bologna, Italy; and (3) providing a novel validation methodology that builds on open data provided by navigation service, which we leverage to assess the quality of the proposed Bologna dataset. These three contributions are expected to benefit the whole research community, since they not only provide a new ready-to-use realistic dataset that can be input to network simulators but ease the generation and validation of further vehicular mobility traces for networking research as well.