# Scientific Publications

## Accepted (in publication)

1. , “Towards Adaptive Car-to-Cloud Communication”, in 4th IEEE International Workshop on Pervasive Context-Aware Smart Cities and Intelligent Transport Systems (PerAwareCity’19), Athens, Greece, Mar. 2019. [BibTeX file, PDF]
@inproceedings{herrnleben2019adaptive,
author = {Herrnleben, Stefan and Pfannem{\"{u}}ller, Martin and Krupitzer, Christian and Kounev, Samuel and Segata, Michele and Fastnacht, Felix and Nigmann, Magnus},
title = {{Towards Adaptive Car-to-Cloud Communication}},
booktitle = {4th IEEE International Workshop on Pervasive Context-Aware Smart Cities and Intelligent Transport Systems (PerAwareCity'19)},
year = {2019},
month = {March},
publisher = {IEEE},
note = {to appear}
}

Recent developments in communication technology have led to cloud resources becoming ubiquitous. These resources enable many new applications by offering computational power for remote embedded devices. In combination with advances in the area of smart driving, this seems to be especially beneficial for applications such as remote maintenance of vehicles or integration with smart city services. As autonomous driving continues to gain traction, Car-to-Cloud communication can support transferring collected data to the cloud, e.g., for dynamic learning of new map information. Additionally, passengers can benefit from novel entertainment services. All these developments require a stable connection between a mobile vehicle and the cloud resources. In this vision paper, we survey Car-to-Cloud communication applications. Based on the analysis of the varying requirements for these applications, we formulate research questions and challenges. Further, we discuss how these challenges can be addressed by means of an adaptive Car-to-Cloud communication middleware. We conclude with an overview on our activities in this area and an outlook on our planned future work on adaptive communication.

## Book chapters

1. , “Veins – the open source vehicular network simulation framework”, in Recent Advances in Network Simulation, Springer, 2019. [BibTeX file]
@incollection{sommer2019veins,
author = {Sommer, Christoph and Eckhoff, David and Brummer, Alexander and Buse, Dominik S. and Hagenauer, Florian and Joerer, Stefan and Segata, Michele},
editor = {Virdis, Antonio and Kirsche, Michael},
title = {{Veins {--} the open source vehicular network simulation framework}},
booktitle = {Recent Advances in Network Simulation},
year = {2019},
publisher = {Springer},
isbn = {978-3-030-12841-8},
i7index = {to-appear}
}


## Journal articles

1. , “Platooning Maneuvers in Vehicular Networks: a Distributed and Consensus-Based Approach”, IEEE Transactions on Intelligent Vehicles, vol. 4, no. 1, pp. 59–72, Mar. 2019. [BibTeX file, PDF]
@article{santini2019platooning,
author = {Santini, Stefania and Salvi, Alessandro and Valente, Antonio Saverio and Pescap{\{e}}, Antonio and Segata, Michele and Lo Cigno, Renato},
title = {{Platooning Maneuvers in Vehicular Networks: a Distributed and Consensus-Based Approach}},
journal = {IEEE Transactions on Intelligent Vehicles},
pages = {59-72},
volume = {4},
number = {1},
year = {2019},
month = {March},
publisher = {IEEE},
doi = {10.1109/TIV.2018.2886677}
}

Cooperative driving is an essential component of future intelligent road systems. It promises greater safety, reducing accidents due to drivers distraction, improved infrastructure utilization, and fuel consumption reduction with platooning applications. Proper platoon management requires Inter-Vehicular Communication (IVC), longitudinal control and stability, lateral control for and safety, and protocols, proper application and platoons, algorithms to manage and perform coordinated maneuvers.This work shows how a longitudinal controller based on distributed consensus can, at the same time, guarantee stability and performance in regime platoon operations, and protocols, be at the hearth of maneuvering and algorithms, as it remains stable in face of changes of platoon topology and system, control gains. The adoption of a single control algorithm for two fundamental tasks greatly simplify the overall design of the and stability, improves and mobility, safety as it is not required to switch between different controllers during platoon operation. The theoretical properties are proven in the first part of the paper. The second part of the paper is devoted to its implementation in a state-of- the-art and IVC simulator, which is used for an extensive experimental campaign showing the dynamic properties of the system and its performance in a set of typical platoon maneuvers as join, leave and inclusion of a vehicle in the middle of the platoon. All simulations include realistic details of the vehicle dynamics (mass, dimensions, power train dynamics) as well as extremely detailed modeling of the communication network, from 802.11p protocol details, to collisions, packet errors, path loss and fading on the channel, and delays., source-destination based
2. , “Cooperative Driving and the Tactile Internet”, Proceedings of the IEEE, vol. 107, no. 2, pp. 436–446, Feb. 2019. [BibTeX file, PDF]
@article{dressler2019cooperative,
author = {Dressler, Falko and Klingler, Florian and Segata, Michele and Lo Cigno, Renato},
title = {{Cooperative Driving and the Tactile Internet}},
journal = {Proceedings of the IEEE},
pages = {436-446},
volume = {107},
number = {2},
year = {2019},
month = {February},
publisher = {IEEE},
doi = {10.1109/JPROC.2018.2863026}
}

The trend towards autonomous driving and the recent advances in vehicular networking led to a number of very successful proposals towards cooperative driving. Maneuvers can be coordinated among participating vehicles and controlled by means of wireless communications. One of the most challenging scenario or application in this context is Cooperative Adaptive Cruise Control (CACC) or platooning. When it comes to realizing safety gaps between the cars of less than 5m, very strong requirements on the communication system need to be satisfied. The underlying distributed control system needs regular updates of sensor information from the other cars in the order of about 10 Hz. This leads to message rates in the order of up to 10 kHz for large networks, which, given the possibly unreliable wireless communication and the critical network congestion, is beyond the capabilities of current vehicular networking concepts. In this article, we summarize the concepts of networked control systems and revisit the capabilities of current vehicular networking approaches. We then present opportunities of Tactile Internet concepts that integrate interdisciplinary approaches from both control theory, mechanical engineering, and communication protocol design. This way, it becomes possible to solve the high reliability and latency issues in this context.
3. , “Performance Assessment of IEEE 802.11p with an Open Source SDR-based Prototype”, IEEE Transactions on Mobile Computing, vol. 17, no. 5, pp. 1162–1175, May 2018. [BibTeX file, PDF]
@article{bloessl2018performance,
author = {Bloessl, Bastian and Segata, Michele and Sommer, Christoph and Dressler, Falko},
title = {{Performance Assessment of IEEE 802.11p with an Open Source SDR-based Prototype}},
journal = {IEEE Transactions on Mobile Computing},
pages = {1162-1175},
volume = {17},
number = {5},
year = {2018},
month = {May},
publisher = {IEEE},
doi = {10.1109/TMC.2017.2751474}
}

We present a complete simulation and experimentation framework for IEEE 802.11p. The core of the framework is an SDR-based OFDM transceiver that we validated extensively by means of simulations, interoperability tests, and, ultimately, by conducting a field test. Being SDR-based, the transceiver offers important benefits: It provides access to all data down to and including the physical layer, allowing for a better understanding of the system. Based on open and programmable hardware and software, the transceiver is completely transparent and all implementation details can be studied and, if needed, modified. Finally, it enables a seamless switch between simulations and experiments and, thus, helps to bridge the gap between theory and practice. Comparing the transceiver’s performance with independent results from simulations and experiments, we underline its potential to be used as a tool for further studies of IEEE 802.11p networks both in field operational tests as well as for simulation-based development of novel physical layer solutions. To make the framework accessible to fellow researchers and to allow reproduction of the results, we released it under an Open Source license.
4. , “A Consensus-based Approach for Platooning with Inter-Vehicular Communications and its Validation in Realistic Scenarios”, IEEE Transactions on Vehicular Technology, vol. 66, no. 3, pp. 1985–1999, Mar. 2017. [BibTeX file, PDF]
@article{santini2017consensusbased,
author = {Santini, Stefania and Salvi, Alessandro and Valente, Antonio Saverio and Pescap{\{e}}, Antonio and Segata, Michele and Lo Cigno, Renato},
title = {{A Consensus-based Approach for Platooning with Inter-Vehicular Communications and its Validation in Realistic Scenarios}},
journal = {IEEE Transactions on Vehicular Technology},
pages = {1985-1999},
volume = {66},
number = {3},
keywords = {Lyapunov-Razumikhin;Platooning;V2V;VANET;distributed consensus;multiple time-varying communication delays},
year = {2017},
month = {March},
publisher = {IEEE},
issn = {0018-9545},
doi = {10.1109/TVT.2016.2585018}
}

Automated and coordinated vehicles’ driving (platooning) is very challenging due to the multi-body control complexity and the presence of unreliable, time-varying wireless Inter-Vehicular Communication (IVC). We propose a novel controller for vehicle platooning based on consensus and analytically demonstrate its stability and dynamic properties. Traditional approaches assume the logical control topology as a constraint fixed a priori, and the control law is designed consequently; our approach makes the control topology a design parameter that can be exploited to reconfigure the controller depending on the needs and scenario characteristics. Furthermore, the controller automatically compensates outdated information caused by network losses and delays. The controller is implemented in PLEXE, a state of the art IVC and mobility simulator that includes basic building blocks for platooning. Analysis and simulations show the controller robustness and performance in several scenarios, including realistic propagation conditions with interference caused by other vehicles. We compare our approach against a controller taken from literature, which is generally considered among the most performing ones. Finally, we test the proposed controller by implementing the real dynamics (engine, transmission, braking systems, etc.) of heterogeneous vehicles in PLEXE and verifying that platoons remain stable and safe regardless of real life impairments that cannot be modeled in the analytic solution. The results show the ability of the proposed approach to maintain a stable string of realistic vehicles with different control-communication topologies even in the presence of strong interference, delays, and fading conditions, providing higher comfort and safety for platoon drivers.
5. , “Let’s Talk in Groups: A Distributed Bursting Scheme for Cluster-based Vehicular Applications”, Elsevier Vehicular Communications, vol. 8, pp. 2–12, Apr. 2017. [BibTeX file, PDF]
@article{segata2017lets,
author = {Segata, Michele and Dressler, Falko and Lo Cigno, Renato},
title = {{Let's Talk in Groups: A Distributed Bursting Scheme for Cluster-based Vehicular Applications}},
journal = {Elsevier Vehicular Communications},
pages = {2-12},
volume = {8},
year = {2017},
month = {April},
publisher = {Elsevier},
doi = {10.1016/j.vehcom.2016.11.006}
}

Clustering has been an important concept in the scope of vehicular networks. The idea is to reduce channel contention, enable building backbones and might improve spatial reuse. We propose a seemingly simple, yet unexplored idea: extending IEEE 802.11 frame bursting MAC access to multiple stations aggregated into a cluster. We call this approach Distributed EDCA Bursting (DEB). The focus of our work is not on building clusters, but exploring what is the gain that can be achieved by the standard IEEE 802.11p channel access if we introduce the principle of frame bursting (presently not allowed in IEEE 802.11p standard, but the key factor for the efficiency of IEEE 802.11n/ac WiFi channel access). The fundamental idea is to extend the standard frame bursting mechanism so that only the cluster head contends for the channel. Upon winning the contention, the reserved transmission opportunity is shared among the vehicles in the cluster, which transmit a coordinated burst of frames. We describe the idea in detail, particularly analyzing theoretical benefits and limitations of the approach. We implement DEB in the platooning simulation framework Plexe-Veins and analyze its behavior under different loads (i.e., number of vehicles sharing the channel), transmit power policies, and different MAC and physical layer parameters. We present benefits and drawbacks of our approach, showing that it can overcome channel limits in saturation conditions, reduce channel usage at moderate loads, and improve spatial reuse. Moreover, by coordinating and distributing channel access, DEB reduces the number of collisions at the expenses of a slightly increased average beacon inter-arrival time.
6. , “Enabling Situation Awareness at Intersections for IVC Congestion Control Mechanisms”, IEEE Transactions on Mobile Computing, vol. 15, no. 7, pp. 1674–1685, Jun. 2016. [BibTeX file, PDF]
@article{joerer2016enabling,
author = {Joerer, Stefan and Bloessl, Bastian and Segata, Michele and Sommer, Christoph and Lo Cigno, Renato and Jamalipour, Abbas and Dressler, Falko},
title = {{Enabling Situation Awareness at Intersections for IVC Congestion Control Mechanisms}},
journal = {IEEE Transactions on Mobile Computing},
pages = {1674-1685},
volume = {15},
number = {7},
year = {2016},
month = {June},
publisher = {IEEE},
doi = {10.1109/TMC.2015.2474370}
}

Intersection Assistance Systems (IAS) aim to assist road users in avoiding collisions at intersections, either by warning the driver or by triggering automated actions. Such a system can be realized based on passive scanning only (e.g., using LiDAR) or supported by active Inter-Vehicle Communication (IVC). The main reason to use IVC is its ability to provide situation awareness even when a possible crash candidate is not yet in visual range. The IVC research community has identified beaconing, i.e., one-hop broadcast, as the primary communication primitive for vehicular safety applications. Recently, adaptive beaconing approaches have been studied and different congestion control mechanisms have been proposed to cope with the diverse demands of vehicular networks. In this paper, we show that current state-of-the-art congestion control mechanisms are not able to support IAS adequately. Specifically, current approaches fail due to their inherent fairness postulation, i.e., they lack fine grained prioritization. We propose a solution that extends congestion control mechanisms by allowing temporary exceptions for vehicles in dangerous situations, that is, situation-based rate adaptation. We show the applicability for two state-of-the-art congestion control mechanisms, namely Transmit Rate Control (TRC) and Dynamic Beaconing (DynB), in two different vehicular environments, rural and downtown.
7. , “Towards Communication Strategies for Platooning: Simulative and Experimental Evaluation”, IEEE Transactions on Vehicular Technology, vol. 64, no. 12, pp. 5411–5423, Dec. 2015. [BibTeX file, PDF]
@article{segata2015communication,
author = {Segata, Michele and Bloessl, Bastian and Joerer, Stefan and Sommer, Christoph and Gerla, Mario and Lo Cigno, Renato and Dressler, Falko},
title = {{Towards Communication Strategies for Platooning: Simulative and Experimental Evaluation}},
journal = {IEEE Transactions on Vehicular Technology},
pages = {5411-5423},
volume = {64},
number = {12},
year = {2015},
month = {December},
publisher = {IEEE},
doi = {10.1109/TVT.2015.2489459}
}

Platooning, the idea of cars autonomously following their leaders to form a road train, has huge potentials to improve traffic flow efficiency and, most importantly, road traffic safety. Wireless communication is a fundamental building block - it is needed to manage and to maintain the platoons. To keep the system stable, strict constraints in terms of update frequency and communication reliability must be met. We investigate different communication strategies by explicitly taking into account the requirements of the controller, exploiting synchronized communication slots as well as transmit power adaptation. As a baseline, we compared the proposed approaches to two state of the art adaptive beaconing protocols that have been designed for cooperative awareness applications, namely ETSI DCC and DynB. Our simulation models have been parameterized and validated by means of real-world experiments. Our results demonstrate that the combination of synchronized communication slots with transmit power adaptation is perfectly suited for cooperative driving applications, even in very crowded freeway scenarios.
8. , “How Shadowing Hurts Vehicular Communications and How Dynamic Beaconing Can Help”, IEEE Transactions on Mobile Computing, vol. 14, no. 7, pp. 1411–1421, Jul. 2015. [BibTeX file, PDF]
@article{sommer2015how,
author = {Sommer, Christoph and Joerer, Stefan and Segata, Michele and Tonguz, Ozan K. and Lo Cigno, Renato and Dressler, Falko},
title = {{How Shadowing Hurts Vehicular Communications and How Dynamic Beaconing Can Help}},
journal = {IEEE Transactions on Mobile Computing},
pages = {1411-1421},
volume = {14},
number = {7},
year = {2015},
month = {July},
publisher = {IEEE},
doi = {10.1109/TMC.2014.2362752}
}

We study the effect of radio signal shadowing dynamics, caused by vehicles and by buildings, on the performance of beaconing protocols in Inter-Vehicular Communication (IVC). Recent research indicates that beaconing, i.e., one hop message broadcast, shows excellent characteristics and can outperform other communication approaches for both safety and efficiency applications, which require low latency and wide area information dissemination, respectively. To mitigate the broadcast storm problem, adaptive beaconing solutions have been proposed and designed. We show how shadowing dynamics of moving obstacles hurt IVC, reducing the performance of beaconing protocols. To the best of our knowledge, this is one of the first studies on identifying the problem and the underlying challenges and proposing the opportunities presented by such challenges. Shadowing also limits the risk of overloading the wireless channel. We demonstrate how these challenges and opportunities can be taken into account and outline a novel approach to dynamic beaconing. It provides low-latency communication (i.e., very short beaconing intervals), while ensuring not to overload the wireless channel. The presented simulation results substantiate our theoretical considerations.
9. , “A Vehicular Networking Perspective on Estimating Vehicle Collision Probability at Intersections”, IEEE Transactions on Vehicular Technology, vol. 63, no. 4, pp. 1802–1812, May 2014. [BibTeX file, PDF]
@article{joerer2014vehicular,
author = {Joerer, Stefan and Segata, Michele and Bloessl, Bastian and Lo Cigno, Renato and Sommer, Christoph and Dressler, Falko},
title = {{A Vehicular Networking Perspective on Estimating Vehicle Collision Probability at Intersections}},
journal = {IEEE Transactions on Vehicular Technology},
pages = {1802-1812},
volume = {63},
number = {4},
year = {2014},
month = {May},
publisher = {IEEE},
doi = {10.1109/TVT.2013.2287343}
}

Finding viable metrics to assess the effectiveness of Intelligent Transportation Systems (ITS) in terms of ’safety’ is one of the major challenges in vehicular networking research. We aim to provide a metric, an estimation of the vehicle collision probability at intersections, that can be used for evaluating Inter-Vehicle Communication (IVC) concepts. In the last years, the vehicular networking community reported in several studies that safety enhancing protocols and applications cannot be evaluated based only on networking metrics like delays and packet loss rates. We present an evaluation scheme that addresses this need by quantifying the probability of a future crash, depending on the situation in which a vehicle is receiving a beacon message (e.g., a CAM or a BSM). Thus, our criticality metric also allows for fully distributed situation assessment. We investigate the impact of safety messaging between cars approaching an intersection using a modified road traffic simulator that allows selected vehicles to disregard traffic rules. As direct result we show that simple beaconing is not as effective as anticipated in suburban environments. More profoundly, however, our simulation results reveal more details about the timeliness (regarding the criticality assessment) of beacon messages, and as such, can be used to develop more sophisticated beaconing solutions.
10. , “Automatic Emergency Braking - Realistic Analysis of Car Dynamics and Network Performance”, IEEE Transactions on Vehicular Technology, vol. 62, no. 9, pp. 4150–4161, Oct. 2013. [BibTeX file, PDF]
@article{segata2013automatic,
author = {Segata, Michele and Lo Cigno, Renato},
title = {{Automatic Emergency Braking - Realistic Analysis of Car Dynamics and Network Performance}},
journal = {IEEE Transactions on Vehicular Technology},
pages = {4150-4161},
volume = {62},
number = {9},
year = {2013},
month = {October},
publisher = {IEEE},
doi = {10.1109/TVT.2013.2277802}
}

Safety applications are among the key drivers in vehicular ad hoc network (VANET) research, and their true performance can be only assessed if the application and the communication network are jointly considered. This paper presents a simulation study of an emergency braking (EB) application accomplished by embedding mobility, cars’ dynamic, and drivers’ behavior models into a detailed networking simulator (ns-3). The overall system allows capturing the interactions of the communications with the car’s automated braking mechanism (ABM) and the driver’s behavior. At the same time, it yields very detailed information on the communication level. In addition to the integrated tool, this paper presents a novel and simple message aggregation mechanism to empower message repropagation while controlling the network congestion during the peak load due to EB. Then, it discusses the effectiveness of such applications as a function of the market penetration rate (MPR), showing that even cars that are not equipped with communication devices benefit from the smoother and earlier reaction of the cars that can communicate. Fading phenomena and sensitivity to the radio transmitted power are analyzed, whereas the fine-grained dynamics of cars’ collisions, taking into account different masses and different elastic coefficients, are introduced to evaluate the severity of impacts.
11. , “A Simulation Tool for Automated Platooning in Mixed Highway Scenarios”, ACM SIGMOBILE Mobile Computing and Communications Review, vol. 16, no. 4, pp. 46–49, Oct. 2012. [BibTeX file, PDF]
@article{segata2012simulation2,
author = {Segata, Michele and Dressler, Falko and Lo Cigno, Renato and Gerla, Mario},
title = {{A Simulation Tool for Automated Platooning in Mixed Highway Scenarios}},
journal = {ACM SIGMOBILE Mobile Computing and Communications Review},
pages = {46-49},
volume = {16},
number = {4},
year = {2012},
month = {October},
publisher = {ACM},
doi = {10.1145/2436196.2436218},
i7acmizer = {http://dl.acm.org/authorize?6897512}
}

Automated platooning is one of the most challenging fields in the domain of Intelligent Transportation Systems (ITS). Conceptually, platooning means creating clusters of vehicles which closely follow each other autonomously without action of the driver, neither for accelerating, nor for braking. This leads to several important benefits from substantially improved road throughput to increased safety. The control of such platoons depends on two components: First, radar is typically to be used to control the distance between the vehicles, and secondly, Inter-Vehicle Communication (IVC) helps managing the entire platoon allowing cars to join or to leave the group whenever necessary. Platooning systems have been mostly investigated in controlled environments such as dedicated highways with centralized management. However, platooning-enabled cars will be deployed gradually and might have to travel on highways together with other non-automated vehicles. We developed a combined traffic and network simulator for studying strategies and protocols needed for managing platoons in such mixed scenarios. We show the models needed and present first results using a simple IVC-based platoon management as a proof of concept.

## Conferences and workshops

1. , “RoRoute: Tools to Experiment with Routing Protocols in WMNs”, in 14th IEEE/IFIP Conference on Wireless On demand Network Systems and Services (WONS 2018), Isola 2000, France, Feb. 2018. [BibTeX file, PDF]
@inproceedings{segata2018roroute,
author = {Segata, Michele and Facchi, Nicol{\{o}} and Maccari, Leonardo and Lo Cigno, Renato},
title = {{RoRoute: Tools to Experiment with Routing Protocols in WMNs}},
booktitle = {14th IEEE/IFIP Conference on Wireless On demand Network Systems and Services (WONS 2018)},
year = {2018},
month = {February},
publisher = {IEEE},
doi = {10.23919/WONS.2018.8311668}
}

Routing in wireless mesh networks is a well studied topic, but indeed, a deeper analysis in real world deployments shows that there are still many open issues, the real world is complex enough so that theoretic design, simulations and emulators can hardly encode it. This paper presents a set of tools and best practices we developed thanks to the WiSHFUL experimental platform that enables the analysis of routing protocols robustness and resilience in face of failures and other impairments when the protocols run in real networks with all the complexity and non-linear interactions that characterize wireless meshes. We present results obtained with Optimized Link State Routing (OLSR) and possible extensions to this protocol that clearly document phenomena that are not visible or implementable in either simulation or emulation environments.
2. , “Towards Infrastructure-Aided Self-Organized Hybrid Platooning”, in IEEE Global Conference on Internet of Things (GCIoT 2018), Alexandria, Egypt, Dec. 2018. [BibTeX file, PDF]
@inproceedings{krupitzer2018infrastructureaided,
author = {Krupitzer, Christian and Segata, Michele and Breitbach, Martin and El-Tawab, Samy S. and Tomforde, Sven and Becker, Christian},
title = {{Towards Infrastructure-Aided Self-Organized Hybrid Platooning}},
booktitle = {IEEE Global Conference on Internet of Things (GCIoT 2018)},
year = {2018},
month = {December},
publisher = {IEEE},
doi = {10.1109/GCIoT.2018.8620134}
}

Nowadays, the technical feasibility of autonomous driving is out of the question. This technology opens the door for several research topics (e.g., information exchange, security of information) in the IoT domain. One such application is platooning: coordinated driving of vehicles in convoys. Therefore, such platoons set up Internets-of-Vehicles. Although platooning has been mainly researched on highways, the idea of platooning in smart cities can have several benefits, such as efficient use of roads, time-saving through route optimization, and minimizing traffic in peak times. In this paper, we present a traffic management approach for combining platooning on highways and urban areas. We explain the idea of platooning, how to manage it efficiently, and the differences between platooning on the freeway and in smart cities. Finally, we explore the exchange of information in these systems and highlight on information security.
3. , “A LiDAR Error Model for Cooperative Driving Simulations”, in 10th IEEE Vehicular Networking Conference (VNC 2018), Taipei, Taiwan, Dec. 2018. [BibTeX file, PDF]
@inproceedings{segata2018lidar,
author = {Segata, Michele and Lo Cigno, Renato and Bhadani, Rahul Kumar and Bunting, Matthew and Sprinkle, Jonathan},
title = {{A LiDAR Error Model for Cooperative Driving Simulations}},
booktitle = {10th IEEE Vehicular Networking Conference (VNC 2018)},
year = {2018},
month = {December},
publisher = {IEEE},
doi = {10.1109/VNC.2018.8628408},
i7award = {Best Paper Award}
}

Cooperative driving and vehicular network simulations have done huge steps toward high realism. They have become essential tools for performance evaluation of any kind of vehicular networking application. Yet, cooperative vehicular applications will not be built on top of wireless networking alone, but rather fusing together different data sources including sensors like radars, LiDARs, or cameras. So far, these sensors have been assumed to be ideal, i.e., without any measurement error. This paper analyzes a set of estimated distance traces obtained with a LiDAR sensor and develops a stochastic error model that can be used in cooperative driving simulations. After implementing the model within the Plexe simulation framework, we show the impact of the model on a set of cooperative driving control algorithms.
4. , “Centrality-based Route Recovery in Wireless Mesh Networks”, in IEEE International Conference on Communications (ICC 2018), Kansas City, MO, May 2018. [BibTeX file, PDF]
@inproceedings{segata2018centrality,
author = {Segata, Michele and Facchi, Nicol{\{o}} and Maccari, Leonardo and Gemmi, Gabriele and Lo Cigno, Renato},
title = {{Centrality-based Route Recovery in Wireless Mesh Networks}},
booktitle = {IEEE International Conference on Communications (ICC 2018)},
year = {2018},
month = {May},
publisher = {IEEE},
doi = {10.1109/ICC.2018.8422821}
}

Wireless Mesh Networks are subject to frequent node and link failures, and routing protocols currently used, such as Optimized Link State Routing (OLSR) or Babel (Babel), suffer from relatively long recovery times characterized by broken and looped routes due to long timeouts that can not be shortened to keep the overhead at an acceptable level. This paper experiments a novel timer management technique named Pop-Routing on top of OLSR. Pop-Routing exploits the notion of betweenness centrality to tune timers depending on the node position in the network, so that failures that lead to larger traffic losses can be recovered faster. Pop-Routing maintains the overhead constant, but favors the most central nodes, whose failure is devastating from the performance point of view, and penalizes peripheral ones and leaves of the topology, whose failure has a very little impact on the entire network. Pop-Routing has been implemented as a plug-in in the OLSR daemon, coupled with an external process, named Prince, that computes centrality and timer values without interfering with the routing daemon. Experiments are run on the WiSHFUL showing the benefit of Pop-tuning of OLSR Hello and Traffic Control timers.
5. , “Communication-based Collision Avoidance between Vulnerable Road Users and Cars”, in 3rd IEEE INFOCOM Workshop on Smart Cities and Urban Computing (SmartCity 2017), Atlanta, GA, May 2017. [BibTeX file, PDF]
@inproceedings{segata2017communicationbased,
author = {Segata, Michele and Vijeikis, Romas and Lo Cigno, Renato},
title = {{Communication-based Collision Avoidance between Vulnerable Road Users and Cars}},
booktitle = {3rd IEEE INFOCOM Workshop on Smart Cities and Urban Computing (SmartCity 2017)},
year = {2017},
month = {May},
publisher = {IEEE},
doi = {10.1109/INFCOMW.2017.8116439}
}

The advent of wireless communication for vehicles paves the road for a bounty of cooperative applications: The most interesting being cooperative safety awareness. By exchanging information vehicles can become aware of each other and prevent dangerous situations that can lead to crashes either by early warning drivers or by automatic vehicle control, a solution particularly appealing for self-driving cars. While research on vehicular safety mainly focuses on vehicle-to-vehicle safety, we can exploit communication to implement applications aimed at protecting vulnerable road users, such as pedestrians or cyclists. In this paper, we start by exploiting a probability framework for estimating the likelihood of collision between a vehicles approaching an intersection and a cyclist, in light of the feasibility of communication between the two. On top of this framework, we design a simple application that, under certain conditions, informs the car driver (assumed to have to yield precedence) of the possible collision. We model the reaction of the driver to the warning and analyze possible benefits and drawbacks of such an application. The contribution is not the application itself, which is obvious, but the insights in the results in light of communication capabilities and human reaction that provide a specific set of aspects that should be considered in the design of such a safety system.
6. , “RoCoSys: A Framework for Coordination of Mobile IoT Devices”, in 1st International Workshop on Mobile and Pervasive Internet of Things (PerIoT 2017), Big Island, HI, Mar. 2017, pp. 485–490. [BibTeX file, PDF]
@inproceedings{krupitzer2017rocosys,
author = {Krupitzer, Christian and Breitbach, Martin and Saal, Johannes and Becker, Christian and Segata, Michele and Lo Cigno, Renato},
title = {{RoCoSys: A Framework for Coordination of Mobile IoT Devices}},
booktitle = {1st International Workshop on Mobile and Pervasive Internet of Things (PerIoT 2017)},
pages = {485-490},
year = {2017},
month = {March},
publisher = {IEEE},
doi = {10.1109/PERCOMW.2017.7917611}
}

Mobile IoT devices enable new classes of systems, such as cyber-physical systems. These systems pose challenges as they should seamlessly interact with users and other systems. In this paper, we address the problem of interaction between mobile pervasive IoT devices. Our contributions are threefold. First, we present a concept for a framework for coordination of mobile IoT devices. Second, we implement a reusable robot platform using the Mindstorms toolkit and a customizable adaptation logic for their coordination based on our framework. Third, we show its usability with two applications: an intelligent vehicle highway system as well as a smart vacuum cleaner.
7. , “Platooning in SUMO: An Open Source Implementation”, in SUMO User Conference 2017, Berlin, Germany, May 2017, pp. 51–62. [BibTeX file, PDF]
@inproceedings{segata2017platooning,
author = {Segata, Michele},
title = {{Platooning in SUMO: An Open Source Implementation}},
booktitle = {SUMO User Conference 2017},
pages = {51-62},
year = {2017},
month = {May},
publisher = {DLR}
}

Platooning is an application that enhances autonomous driving by means of cooperation. Vehicles, by using wireless communication, exchange data such as position, speed, and acceleration to reduce their inter-vehicle gap and drive in groups, called indeed platoons. The benefits span from improved infrastructure usage to reduced pollution, and from increased safety to a better travel experience. The analysis of a platooning system is complex as it encompasses several research fields, including communication, control theory, traffic engineering, and vehicle dynamics. In addition, even small field operational tests can be extremely expensive in terms of money and time, let alone large scale scenarios. Research studies in platooning can thus highly benefit from simulative analyses, as they overcome the limitations of real world test beds. To this purpose, we developed PLEXE, an extension to the Veins vehicular networking framework that enables the simulation of platooning systems, both from a network and a vehicle dynamics perspective. In this paper we detail the changes PLEXE makes to SUMO to simulate platooning control systems, including realistic engine models for the simulation of vehicle dynamics. In addition, we provide two sample use cases to show its potential.
8. , “On the Effects of Cooperative Platooning on Traffic Shock Waves”, in 9th IEEE Vehicular Networking Conference (VNC 2017), Poster Session, Torino, Italy, Nov. 2017, pp. 37–38. [BibTeX file, PDF]
@inproceedings{terruzzi2017effects,
author = {Terruzzi, Luca and Colombo, Riccardo and Segata, Michele},
title = {{On the Effects of Cooperative Platooning on Traffic Shock Waves}},
booktitle = {9th IEEE Vehicular Networking Conference (VNC 2017), Poster Session},
pages = {37-38},
year = {2017},
month = {November},
publisher = {IEEE},
doi = {10.1109/VNC.2017.8275654}
}

Cooperative platooning has been proposed as a promising solution to traffic congestion, safety, and pollution. A platooning application forms road trains of vehicles that autonomously follow a common leader, separated by a small inter-vehicle gap. In terms of traffic efficiency, platooning should improve the vehicular flow and reduce shock waves. The latter are the cause of start-and-stop dynamics which, besides disrupting traffic flow, can lead to accidents. The aim of this poster is to analyze, by means of simulations, the impact of platoons on both the traffic flow and the formation of shock waves.
9. , “A Joint Network/Control Design for Cooperative Automatic Driving”, in 9th IEEE Vehicular Networking Conference (VNC 2017), Torino, Italy, Nov. 2017, pp. 167–174. [BibTeX file, PDF]
@inproceedings{giordano2017joint,
author = {Giordano, Giulia and Segata, Michele and Blanchini, Franco and Lo Cigno, Renato},
title = {{A Joint Network/Control Design for Cooperative Automatic Driving}},
booktitle = {9th IEEE Vehicular Networking Conference (VNC 2017)},
pages = {167-174},
year = {2017},
month = {November},
publisher = {IEEE},
doi = {10.1109/VNC.2017.8275606}
}

Cooperative automatic driving, or platooning, is a promising solution to improve traffic safety, while reducing congestion and pollution. The design of a control system for this application is a challenging, multi-disciplinary problem, as cooperation between vehicles is obtained through wireless communication. So far, control and network issues of platooning have been investigated separately. In this work we design a cooperative driving system from a joint network and control perspective, determining worst-case upper bounds on the safety distance subject to network losses, so the actual inter-vehicle gap can be tuned depending on vehicle or network performance. By means of simulation, we show that the system is very robust to packet losses and that the derived bounds are never violated.
10. , “On the Feasibility of Collision Detection in Full-Duplex 802.11 Radio”, in 13th IEEE/IFIP Conference on Wireless On demand Network Systems and Services (WONS 2017), Jackson Hole, WY, Feb. 2017, pp. 9–16. [BibTeX file, PDF]
@inproceedings{segata2017feasibility,
author = {Segata, Michele and Lo Cigno, Renato},
title = {{On the Feasibility of Collision Detection in Full-Duplex 802.11 Radio}},
booktitle = {13th IEEE/IFIP Conference on Wireless On demand Network Systems and Services (WONS 2017)},
pages = {9-16},
year = {2017},
month = {February},
publisher = {IEEE},
doi = {10.1109/WONS.2017.7888755}
}

Full-duplex radios are becoming a feasible reality thanks to recent advances in self-interference cancellation. Switching from half- to full-duplex requires a major re-design of many network features and characteristics, including the MAC layer. The literature provides several new proposals or improvements that are applicable in different topologies: centralized, distributed, and multi-hop Wireless LANs (WLANs). These proposals, however, mostly focus on directional, unicast communication. While the main goal of unicast-focused approaches is to get as close as possible to doubling the throughput, it is still unclear how to exploit full-duplex radios in broadcast-like environments such as the vehicular one or in general in WiFi-like scenarios where interference is the dominating impairment. In this work we analyze the possible benefits and drawbacks of exploiting self-interference cancellation in full-duplex radios to implement collision detection. We show that, if proved feasible, the required changes to the MAC layer of an 802.11-based transceiver would be minimal, and could largely improve the performance with respect to a standard collision avoidance mechanism. In addition, the paper discusses the tricky aspects and the parameters required to identify a collision in a wireless network and discusses the many differences between managing collisions in a wired and in a wireless environment.
11. , “Distributed EDCA Bursting: Improving Cluster-based Communication in IVC”, in 17th ACM International Symposium on Mobile Ad Hoc Networking and Computing (MobiHoc 2016), 1st International Workshop on Internet of Vehicles and Vehicles of Internet (IoV-VoI 2016), Paderborn, Germany, Jul. 2016, pp. 13–18. [BibTeX file, PDF]
@inproceedings{segata2016distributed,
author = {Segata, Michele and Goss, Davide and Lo Cigno, Renato},
title = {{Distributed EDCA Bursting: Improving Cluster-based Communication in IVC}},
booktitle = {17th ACM International Symposium on Mobile Ad Hoc Networking and Computing (MobiHoc 2016), 1st International Workshop on Internet of Vehicles and Vehicles of Internet (IoV-VoI 2016)},
pages = {13-18},
year = {2016},
month = {July},
publisher = {ACM},
doi = {10.1145/2938681.2938686}
}

Cluster-based communication is a staple topic in vehicular networks. Clustering communication nodes promise to reduce channel contention, enable building backbones and might improve spatial reuse. In this paper we propose a seemingly simple, yet unexplored idea: extending 802.11 frame bursting MAC access to multiple stations aggregated into a cluster. The focus of the paper is thus not building a cluster, but exploring what is the gain that can be achieved by the standard 802.11p channel access if we introduce the principle of frame bursting (presently not allowed in 802.11p standard, but the key factor for the efficiency of 802.11n/ac WiFi channel access). The key scientific question is if we can extend the frame bursting mechanism so that only the cluster leader contends for the channel reserving a Transmission Opportunity that is used by all the vehicles in the cluster transmitting a coordinated burst of frames. We describe in detail the idea, highlight the problems that can be encountered in its implementation (the devil, as usual is in details), and present some preliminary results for a special class of clusters: Cooperative driving platoons of cars.
12. , “On Platooning Control using IEEE 802.11p in Conjunction with Visible Light Communications”, in 12th IEEE/IFIP Conference on Wireless On demand Network Systems and Services (WONS 2016), Cortina d’Ampezzo, Italy, Jan. 2016, pp. 124–127. [BibTeX file, PDF]
@inproceedings{segata2016platooning,
author = {Segata, Michele and Lo Cigno, Renato and Tsai, Hsin-Mu and Dressler, Falko},
title = {{On Platooning Control using IEEE 802.11p in Conjunction with Visible Light Communications}},
booktitle = {12th IEEE/IFIP Conference on Wireless On demand Network Systems and Services (WONS 2016)},
pages = {124-127},
year = {2016},
month = {January},
publisher = {IEEE}
}

The control of a platoon using IEEE 802.11p is an active research challenge in the field of vehicular networking and cooperative automated vehicles. IEEE 802.11p is a promising technology for direct vehicle to vehicle communication, but there are concerns about its usage for the control of platoons as it suffers packet losses due to congestion in highly dense scenarios. On the other hand, Visible Light Communication (VLC) recently gained attention as a short range technology for vehicular applications. VLC could be used to support or backup IEEE 802.11p, increasing reliability and scalability, and hence the safety of platooning systems. In this paper, we perform a large-scale simulation campaign using VLC integrated with IEEE 802.11p for platooning. We particularly demonstrate the benefits, but also the limitations, of such heterogeneous networking.
13. , “Jerk Beaconing: A Dynamic Approach to Platooning”, in 7th IEEE Vehicular Networking Conference (VNC 2015), Kyoto, Japan, Dec. 2015, pp. 135–142. [BibTeX file, PDF]
@inproceedings{segata2015jerk,
author = {Segata, Michele and Dressler, Falko and Lo Cigno, Renato},
title = {{Jerk Beaconing: A Dynamic Approach to Platooning}},
booktitle = {7th IEEE Vehicular Networking Conference (VNC 2015)},
pages = {135-142},
year = {2015},
month = {December},
publisher = {IEEE},
doi = {10.1109/VNC.2015.7385560}
}

Automated car following, or platooning, is a promising Inter-Vehicle Communication (IVC) application which has the potential of reducing traffic jams, improving safety, and decreasing fuel consumption by forming groups of vehicles which autonomously follow a common leader. The application works by sharing vehicles’ data through high frequency periodic beaconing which, due to channel congestion, might not work in highly dense scenarios. To address this issue, in this paper we propose a dynamic approach called Jerk Beaconing which exploits vehicle dynamics to share data only when needed. The results, compared to a commonly assumed 10Hz beaconing, show huge benefits in term of network resource saving. Moreover, our approach outperforms static beaconing in terms of safety as well, as it is able to keep inter-vehicle distance closer to the desired gap even in highly demanding scenarios.
14. , “A Consensus-based Approach for Platooning with Inter-Vehicular Communications”, in 34th IEEE Conference on Computer Communications (INFOCOM 2015), Hong Kong, China, Apr. 2015, pp. 1158–1166. [BibTeX file, PDF]
@inproceedings{santini2015consensusbased,
author = {Santini, Stefania and Salvi, Alessandro and Valente, Antonio Saverio and Pescap{\{e}}, Antonio and Segata, Michele and Lo Cigno, Renato},
title = {{A Consensus-based Approach for Platooning with Inter-Vehicular Communications}},
booktitle = {34th IEEE Conference on Computer Communications (INFOCOM 2015)},
pages = {1158-1166},
year = {2015},
month = {April},
publisher = {IEEE},
doi = {10.1109/INFOCOM.2015.7218490}
}

Automated and coordinated vehicles’ driving (platooning) is gaining more and more attention today and it represents a challenging scenario heavily relying on wireless Inter-Vehicular Communication (IVC). In this paper, we propose a novel controller for vehicle platooning based on consensus. Opposed to current approaches where the logical control topology is fixed a priori and the control law designed consequently, we design a system whose control topology can be reconfigured depending on the actual network status. Moreover, the controller does not require the vehicles to be radar equipped and automatically compensates outdated information caused by network delays. We define the control law and analyze it in both analytical and simulative way, showing its robustness in different network scenarios. We consider three different wireless network settings: uncorrelated Bernoullian losses, correlated losses using a Gilbert-Elliott channel, and a realistic traffic scenario with interferences caused by other vehicles. Finally, we compare our strategy with another state of the art controller. The results show the ability of the proposed approach to maintain a stable string of vehicles even in the presence of strong interference, delays, and fading conditions, providing higher comfort and safety for platoon drivers.
15. , “PLEXE: A Platooning Extension for Veins”, in 6th IEEE Vehicular Networking Conference (VNC 2014), Paderborn, Germany, Dec. 2014, pp. 53–60. [BibTeX file, PDF]
@inproceedings{segata2014plexe,
author = {Segata, Michele and Joerer, Stefan and Bloessl, Bastian and Sommer, Christoph and Dressler, Falko and Lo Cigno, Renato},
title = {{PLEXE: A Platooning Extension for Veins}},
booktitle = {6th IEEE Vehicular Networking Conference (VNC 2014)},
pages = {53-60},
year = {2014},
month = {December},
publisher = {IEEE},
doi = {10.1109/VNC.2014.7013309}
}

Cooperative driving in general and Cooperative Adaptive Cruise Control (CACC) or platooning in particular require blending control theory, communications and networking, as well as mechanics and physics. Given the lack of an integrated modeling framework and theory as well as the prohibitively high costs of using prototypes for what-if studies, simulation remains the fundamental instrument to evaluate entire cooperative driving systems. This work presents PLEXE, an Open Source extension to Veins that offers researchers a simulation environment able to run experiments in realistic scenarios, taking into account physics and mechanics of the vehicles, communications and networking impairments, and Inter-Vehicle Communication (IVC) protocol stacks. PLEXE is easily extensible and already implements protocols to support platooning and cooperative driving applications and several state of the art cruise control models. We describe the structure of the simulator and the control algorithms that PLEXE implements and provide two use cases which show the potential of our framework as a powerful research tool for cooperative driving systems.
16. , “Towards Energy Efficient Smart Phone Applications: Energy Models for Offloading Tasks into the Cloud”, in IEEE International Conference on Communications (ICC 2014), Sydney, Australia, Jun. 2014, pp. 2394–2399. [BibTeX file, PDF]
@inproceedings{segata2014towards,
author = {Segata, Michele and Bloessl, Bastian and Sommer, Christoph and Dressler, Falko},
booktitle = {IEEE International Conference on Communications (ICC 2014)},
pages = {2394-2399},
year = {2014},
month = {June},
publisher = {IEEE},
doi = {10.1109/ICC.2014.6883681}
}

17. , “Supporting Platooning Maneuvers through IVC: An Initial Protocol Analysis for the Join Maneuver”, in 11th IEEE/IFIP Conference on Wireless On demand Network Systems and Services (WONS 2014), Obergurgl, Austria, Apr. 2014, pp. 130–137. [BibTeX file, PDF]
@inproceedings{segata2014supporting,
author = {Segata, Michele and Bloessl, Bastian and Joerer, Stefan and Dressler, Falko and Lo Cigno, Renato},
title = {{Supporting Platooning Maneuvers through IVC: An Initial Protocol Analysis for the Join Maneuver}},
booktitle = {11th IEEE/IFIP Conference on Wireless On demand Network Systems and Services (WONS 2014)},
pages = {130-137},
keywords = {Inter-Vehicle Communications; Autonomous Driving; Platooning;},
year = {2014},
month = {April},
publisher = {IEEE},
doi = {10.1109/WONS.2014.6814733}
}

Driving vehicles in platoons has the potential to improve trafficefficiency, increase safety, reduce fuel consumption, and make drivingexperience more enjoyable. A lot of effort is being spent in thedevelopment of technologies, like radars, enabling automated cruise controlfollowing and ensuring emergency braking if the driver does not react intime; but these technologies alone do not empower real platooning. Theinitial idea of building dedicated infrastructures for platoons, has beenset aside favoring the philosophy that foresees scenarios, where automatedvehicles share the road with human-driven ones. This arises interesting newquestions regarding the interactions between the two categories ofvehicles. In this paper we focus on the analysis of interferences caused bynon-automated vehicles during a Join maneuver. We define the applicationlayer protocol to support the maneuver, together with situations that canprevent successful termination, and describe how they can be detected. Thevalidity of the approach is proven by means of simulations, showing eitherthat the maneuver can successfully be performed, or safely be aborted.Finally, we analyze the impact of the Packet Error Rate on the failure rateof the maneuver, showing that packet losses mainly affect the maneuver froma coordination point of view, rather than stability of the system, i.e.,even at high loss rates, cars never violated a minimum safety distance.
18. , “Fairness Kills Safety: A Comparative Study for Intersection Assistance Applications”, in 25th IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC 2014), Washington, D.C., Sep. 2014, pp. 1442–1447. [BibTeX file, PDF]
@inproceedings{joerer2014fairness,
author = {Joerer, Stefan and Bloessl, Bastian and Segata, Michele and Sommer, Christoph and Lo Cigno, Renato and Dressler, Falko},
title = {{Fairness Kills Safety: A Comparative Study for Intersection Assistance Applications}},
booktitle = {25th IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC 2014)},
pages = {1442-1447},
year = {2014},
month = {September},
publisher = {IEEE},
doi = {10.1109/PIMRC.2014.7136395}
}

We study the ability of Inter-Vehicle Communication (IVC) solutions to handle real-time requirements in safety scenarios using beaconing as a communication primitive. One of the envisioned safety applications is intersection assistance. The objective of such applications is to either warn the driver or even to act autonomously if other approaching vehicles endanger the vehicle. Fairness, combined with aggressive channel access for low-latency safety messages, has been one of the main research line according to which state of the art congestion control mechanisms have been developed. We show that these solutions are not able to sufficiently support intersection assistance applications. Specifically, we show that current approaches fail exactly due to their fairness postulation. We propose a new situation-aware solution to this fairness dilemma by allowing temporary exceptions for vehicles in dangerous situations. We show the applicability for two state of the art congestion control mechanisms, namely ETSI Transmit Rate Control (TRC) and Dynamic Beaconing (DynB). Our investigation also reveals important research objectives for future IVC protocols, namely how much reactivity and situation-awareness is needed in the highly dynamic environment of vehicular networks.
19. , “Towards Inter-Vehicle Communication Strategies for Platooning Support”, in 7th IFIP/IEEE International Workshop on Communication Technologies for Vehicles (Nets4Cars 2014-Fall), Saint-Petersburg, Russia, Oct. 2014, pp. 1–6. [BibTeX file, PDF]
@inproceedings{segata2014intervehicle,
author = {Segata, Michele and Bloessl, Bastian and Joerer, Stefan and Sommer, Christoph and Gerla, Mario and Lo Cigno, Renato and Dressler, Falko},
title = {{Towards Inter-Vehicle Communication Strategies for Platooning Support}},
booktitle = {7th IFIP/IEEE International Workshop on Communication Technologies for Vehicles (Nets4Cars 2014-Fall)},
pages = {1-6},
year = {2014},
month = {October},
publisher = {IEEE},
doi = {10.1109/Nets4CarsFall.2014.7000903}
}

Platooning, the idea of cars autonomously following their leaders to form a road train, has huge potentials to improve traffic flow efficiency and, most importantly, road traffic safety. Wireless communication is a fundamental building block - it is needed to manage and to maintain the platoons. To keep the system stable, strict constraints in terms of update frequency and reliability must be met. We developed communication strategies by explicitly taking into account the requirements of the controller, exploiting synchronized communication slots as well as transmit power adaptation. The proposed approaches are compared to two state of the art adaptive beaconing protocols that have been designed for generic message dissemination. Our simulation models have been parametrized and validated by means of real-world experiments. We clearly show how taking into account specific requirements can be extremely beneficial even in very crowded freeway scenarios.
20. , “How Shadowing Hurts Vehicular Communications and How Dynamic Beaconing Can Help”, in 32nd IEEE Conference on Computer Communications (INFOCOM 2013), Mini-Conference, Turin, Italy, Apr. 2013, pp. 110–114. [BibTeX file, PDF]
@inproceedings{sommer2013how,
author = {Sommer, Christoph and Joerer, Stefan and Segata, Michele and Tonguz, Ozan K. and Lo Cigno, Renato and Dressler, Falko},
title = {{How Shadowing Hurts Vehicular Communications and How Dynamic Beaconing Can Help}},
booktitle = {32nd IEEE Conference on Computer Communications (INFOCOM 2013), Mini-Conference},
pages = {110-114},
year = {2013},
month = {April},
publisher = {IEEE},
doi = {10.1109/INFCOM.2013.6566745}
}

We study the effect of radio signal shadowing dynamics, caused by vehicles and by buildings, on the performance of beaconing protocols in Inter-Vehicular Communication (IVC). Recent research indicates that beaconing, i.e., one hop message broadcast, shows excellent characteristics and can outperform other communication approaches for both safety and efficiency applications, which require low latency and wide area information dissemination, respectively. We show how shadowing dynamics of moving obstacles hurt IVC, reducing the performance of beaconing protocols. At the same time, shadowing also limits the risk of overloading the wireless channel. To the best of our knowledge, this is the first study identifying the problems and resulting possibilities of such dynamic radio shadowing. We demonstrate how these challenges and opportunities can be taken into account and outline a novel approach to dynamic beaconing. It provides low-latency communication (i.e., very short beaconing intervals), while ensuring not to overload the wireless channel. The presented simulation results substantiate our theoretical considerations.
21. , “Vehicle Shadowing Distribution Depends on Vehicle Type: Results of an Experimental Study”, in 5th IEEE Vehicular Networking Conference (VNC 2013), Boston, MA, Dec. 2013, pp. 242–245. [BibTeX file, PDF]
@inproceedings{segata2013vehicle,
author = {Segata, Michele and Bloessl, Bastian and Joerer, Stefan and Sommer, Christoph and Lo Cigno, Renato and Dressler, Falko},
title = {{Vehicle Shadowing Distribution Depends on Vehicle Type: Results of an Experimental Study}},
booktitle = {5th IEEE Vehicular Networking Conference (VNC 2013)},
pages = {242-245},
year = {2013},
month = {December},
publisher = {IEEE},
doi = {10.1109/VNC.2013.6737623}
}

Simulations play a fundamental role for the evaluation of vehicular network communication strategies and applications’ effectiveness. Therefore, the vehicular networking community is continuously seeking more realistic channel and reception models to provide more reliable results, yet maintaining scalability in terms of computational effort. We investigate the effects of vehicle shadowing on IEEE 802.11p based communication. In particular, we perform a set of real world measurements on a freeway and study the impact of different obstructing vehicles on the received signal power distribution. Different vehicle types not only affect the average received power, but also its distribution, suggesting that the attenuation characteristics of the simulation model need to be tailored to the type of vehicle that obstructs the communication path. Based on these observations, we propose a novel way to compose shadowing and fading models to reproduce the observed effects.
22. , “Towards an Open Source IEEE 802.11p Stack: A Full SDR-based Transceiver in GNURadio”, in 5th IEEE Vehicular Networking Conference (VNC 2013), Boston, MA, Dec. 2013, pp. 143–149. [BibTeX file, PDF]
@inproceedings{bloessl2013towards,
author = {Bloessl, Bastian and Segata, Michele and Sommer, Christoph and Dressler, Falko},
title = {{Towards an Open Source IEEE 802.11p Stack: A Full SDR-based Transceiver in GNURadio}},
booktitle = {5th IEEE Vehicular Networking Conference (VNC 2013)},
pages = {143-149},
year = {2013},
month = {December},
publisher = {IEEE},
doi = {10.1109/VNC.2013.6737601},
i7award = {Best Paper Award}
}

We present the first steps towards an Open Source simulation and experimentation framework for IEEE 802.11p networks. The framework is implemented based on GNURadio, a real-time signal processing framework for use in Software Defined Radio (SDR) systems. The core of the framework is a modular Orthogonal Frequency Division Multiplexing (OFDM) transceiver, which has been thoroughly evaluated: First, we show that its computational demands are so low that it can be run on low-end desktop PCs or laptops and thus, the transceiver is also feasible to use in field operational tests. Secondly, we present simulation results to highlight the transceiver’s capability to study and debug PHY and MAC variants in a reproducible manner. We show that the simulations match very well to a widely accepted error model for IEEE 802.11p networks. Finally, we discuss results from an extensive set of measurements that compare our SDR-based transceiver with commercial grade IEEE 802.11p cards. We made the framework available as Open Source to make the system accessible for other researchers and to allow reproduction of the results. This might also pave the way for future proofing cars by means of fully reconfigurable radios.
23. , “A GNURadio Based Receiver Toolkit for IEEE 802.11a/g/p”, in 19th ACM International Conference on Mobile Computing and Networking (MobiCom 2013), 5th Wireless of the Students, by the Students, for the Students Workshop (S3 2013), Demo Session, Miami, FL, Oct. 2013. [BibTeX file, PDF]
@inproceedings{bloessl2013gnuradio,
author = {Bloessl, Bastian and Segata, Michele and Sommer, Christoph and Dressler, Falko},
booktitle = {19th ACM International Conference on Mobile Computing and Networking (MobiCom 2013), 5th Wireless of the Students, by the Students, for the Students Workshop (S3 2013), Demo Session},
year = {2013},
month = {October},
publisher = {ACM},
i7award = {Best Demo/Poster Award}
}

We present an open source Software Defined Radio (SDR) receiver toolkit that is able to decode OFDM frames of IEEE 802.11a/g/p WiFi in real time. It is the first for GNURadio that supports channel bandwidths of up to 20MHz. The toolkit comprises the physical layer, decoding of MAC frames, and extracting the payload of IEEE 802.11a/g/p frames. It is further possible to access and visualize the data in every step of the decoding process in numerous ways. As an example demonstration, the impact of moving antennas and changing settings can be displayed live in time and frequency domain. Lastly, the decoded frames can be fed to Wireshark and/or received on a Linux network interface. Our receiver toolkit has been well received by the community and is already serving as the basis of further research.
24. , “Decoding IEEE 802.11a/g/p OFDM in Software using GNU Radio”, in 19th ACM International Conference on Mobile Computing and Networking (MobiCom 2013), Demo Session, Miami, FL, Oct. 2013, pp. 159–161. [BibTeX file, PDF]
@inproceedings{bloessl2013decoding,
author = {Bloessl, Bastian and Segata, Michele and Sommer, Christoph and Dressler, Falko},
title = {{Decoding IEEE 802.11a/g/p OFDM in Software using GNU Radio}},
booktitle = {19th ACM International Conference on Mobile Computing and Networking (MobiCom 2013), Demo Session},
pages = {159-161},
year = {2013},
month = {October},
publisher = {ACM},
doi = {10.1145/2500423.2505300},
i7acmizer = {http://dl.acm.org/authorize?N70220}
}

We just released an Open Source receiver that is able to decode IEEE 802.11a/g/p OFDM frames in software. This is the first Software Defined Radio (SDR) based OFDM receiver supporting channel bandwidths up to 20 MHz that is not relying on additional FPGA code. Our receiver comprises all layers up to parsing the MAC header and extracting the payload of IEEE 802.11a/g/p networks. In our demo, visitors can interact live with the receiver while it is decoding over the air frames. The impact of moving the antennas and changing the settings are displayed live in time and frequency domain. Furthermore, the decoded frames are piped to Wireshark where the WiFi traffic can be further investigated. It is possible to access and visualize the data in every decoding step from the raw samples, frame detection, channel estimation, up to the decoded MAC packets. The receiver is completely Open Source and represents one step towards experimental research with SDRs.
25. , “An IEEE 802.11a/g/p OFDM Receiver for GNU Radio”, in ACM SIGCOMM 2013, 2nd ACM SIGCOMM Workshop of Software Radio Implementation Forum (SRIF 2013), Hong Kong, China, Aug. 2013, pp. 9–16. [BibTeX file, PDF]
@inproceedings{bloessl2013ofdmreceiver,
author = {Bloessl, Bastian and Segata, Michele and Sommer, Christoph and Dressler, Falko},
booktitle = {ACM SIGCOMM 2013, 2nd ACM SIGCOMM Workshop of Software Radio Implementation Forum (SRIF 2013)},
pages = {9-16},
year = {2013},
month = {August},
publisher = {ACM},
doi = {10.1145/2491246.2491248},
i7acmizer = {http://dl.acm.org/authorize?6833243}
}

26. , “Simulation of 802.11 PHY/MAC: The Quest for Accuracy and Efficiency”, in 9th IEEE/IFIP Conference on Wireless On demand Network Systems and Services (WONS 2012), Courmayeur, Italy, Jan. 2012, pp. 99–106. [BibTeX file, PDF]
@inproceedings{segata2012simulation,
author = {Segata, Michele and Lo Cigno, Renato},
title = {{Simulation of 802.11 PHY/MAC: The Quest for Accuracy and Efficiency}},
booktitle = {9th IEEE/IFIP Conference on Wireless On demand Network Systems and Services (WONS 2012)},
pages = {99-106},
year = {2012},
month = {January},
publisher = {IEEE},
doi = {10.1109/WONS.2012.6152246}
}

The goal of this work is to highlight and explain the limitations of traditional physical channel models used in network simulators for wireless LANs, with particular reference to VANETs, where these limitations may jeopardize the validity of results, specially for safety applications. The fundamental tradeoff is between simulation time and realism. Indeed, a simulator should provide realistic results as fast as possible, even if several nodes (i.e., hundreds) are considered. Our final goal, beyond this initial contribution, is the development of a stochastic channel model which improves reliability of simulations while increasing computational complexity only marginally. The design of our model is based on the representation of the packet decoding procedure as a Markov Decision (Stochastic) Process (MDP), thus avoiding the computational complexity of the simulation of the entire transmission - propagation - decoding chain bit-by-bit, which can surely provide enough accuracy, but at the price of unacceptable computational (and model) complexity. The paper identifies the key phenomena such as preamble detection, central-frequency misalignment, channel captures, vehicles relative speed, that represent the "state" of the MDP modeling the transmission chain, and propose an MDP structure to exploit it. The focus is on 802.11p and OFDM-based PHY layers, but the model is extensible to other transmission techniques easily. The design is tailored for implementation in ns-3, albeit the modeling principle is general and suitable for every event-driven simulator.
27. , “To Crash or Not to Crash: Estimating its Likelihood and Potentials of Beacon-based IVC Systems”, in 4th IEEE Vehicular Networking Conference (VNC 2012), Seoul, Korea, Nov. 2012, pp. 25–32. [BibTeX file, PDF]
@inproceedings{joerer2012tocrash,
author = {Joerer, Stefan and Segata, Michele and Bloessl, Bastian and Lo Cigno, Renato and Sommer, Christoph and Dressler, Falko},
title = {{To Crash or Not to Crash: Estimating its Likelihood and Potentials of Beacon-based IVC Systems}},
booktitle = {4th IEEE Vehicular Networking Conference (VNC 2012)},
pages = {25-32},
year = {2012},
month = {November},
publisher = {IEEE},
doi = {10.1109/VNC.2012.6407441}
}

Is it possible to estimate some ’safety’ metric to assess the effectiveness of Intelligent Transportation Systems? In particular, we are interested in using Inter-Vehicle Communication (IVC) beaconing for increasing drivers’ safety at intersections. In the last couple of years, the vehicular networking community reported in several studies that simple network metrics are not sufficient to evaluate safety enhancing protocols and applications. We present a classification scheme that allows the quantification of such improvements by determining how many potential crashes happen or can be avoided by a specific IVC approach. Using a modified road traffic simulator that allowed selected vehicles to disregard traffic rules, we investigated the impact of safety messaging between cars approaching an intersection. We show that in suburban environments simple beaconing is not as effective as anticipated. Yet, simple one-hop relaying, e.g., by vehicles parked close to an intersection, can improve drivers’ safety substantially. Since the key purpose of IVC is safety, the paper closes the loop in the evaluation of the effectiveness of vehicular networks as defined today.
28. , “A Simulation Tool for Automated Platooning in Mixed Highway Scenarios”, in 18th ACM International Conference on Mobile Computing and Networking (MobiCom 2012), Poster Session, Istanbul, Turkey, Aug. 2012, pp. 389–391. [BibTeX file, PDF]
@inproceedings{segata2012simulation-tool,
author = {Segata, Michele and Dressler, Falko and Lo Cigno, Renato and Gerla, Mario},
title = {{A Simulation Tool for Automated Platooning in Mixed Highway Scenarios}},
booktitle = {18th ACM International Conference on Mobile Computing and Networking (MobiCom 2012), Poster Session},
pages = {389-391},
year = {2012},
month = {August},
publisher = {ACM},
doi = {10.1145/2348543.2348591},
i7acmizer = {http://dl.acm.org/authorize?6729857}
}

Automated platooning is one of the most challenging fields in the domain of Intelligent Transportation Systems (ITS). Conceptually, platooning means creating clusters of vehicles which closely follow each other autonomously without action of the driver, neither for accelerating, nor for braking. This leads to several important benefits from substantially improved road throughput to increased safety. The control of such platoons depends on two components: First, radar is typically to be used to control the distance between the vehicles, and secondly, Inter-Vehicle Communication (IVC) helps managing the entire platoon allowing cars to join or to leave the group whenever necessary. Platooning systems have been mostly investigated in controlled environments such as dedicated highways with centralized management. However, platooning-enabled cars will be deployed gradually and might have to travel on highways together with other non-automated vehicles. We developed a combined traffic and network simulator for studying strategies and protocols needed for managing platoons in such mixed scenarios. We show the models needed and present first results using a simple IVC-based platoon management as a proof of concept.
29. , “Emergency Braking: a Study of Network and Application Performance”, in 8th ACM International Workshop on Vehicular Internetworking (VANET 2011), Las Vegas, NV, Sep. 2011, pp. 1–10. [BibTeX file, PDF]
@inproceedings{segata2011emergency,
author = {Segata, Michele and Lo Cigno, Renato},
title = {{Emergency Braking: a Study of Network and Application Performance}},
booktitle = {8th ACM International Workshop on Vehicular Internetworking (VANET 2011)},
pages = {1-10},
keywords = {VANET, collaborative adaptive cruise control, emergency braking control, ns-3 simulation, rebroadcast schemes, vehicular networks},
year = {2011},
month = {September},
publisher = {ACM},
isbn = {978-1-4503-0869-4},
doi = {10.1145/2030698.2030700}
}

Safety applications are among the key drivers in VANET research. Their study is complex as it encompasses different disciplines, from wireless networking to car dynamics, to drivers’ behavior, not to mention the economic and legal aspects. This work presents a simulative study of emergency braking applications tackled by embedding a mobility, cars’ dynamic, and driver’s behavior model into a detailed networking simulator (ns-3). The results, derived both at the network and at the application level, capture correctly the interactions of the communications and protocols with the car’s adaptive cruise control system and the driver’s behavior for cars that are not equipped with communication devices. The paper presents in detail the improvements we contribute in simulation techniques and model completeness. It introduces a novel and easy message aggregation technique to empower message re-propagation while controlling the network load during the peak due to the emergency braking. Finally it discusses the effectiveness of such applications as a function of the market penetration rate, showing that even cars that are not equipped with communication devices benefit from the smoother and earlier reaction of those cars that can communicate and whose adaptive cruise control implements a correct deceleration strategy.

## Theses

1. , “Safe and Efficient Communication Protocols for Platooning Control”, PhD Thesis (Dissertation), Institute of Computer Science, Feb. 2016. [BibTeX file, PDF]
@phdthesis{segata2016safe,
author = {Segata, Michele},
referee = {Casetti, Claudio},
advisor = {Dressler, Falko and Lo Cigno, Renato},
title = {{Safe and Efficient Communication Protocols for Platooning Control}},
institution = {Institute of Computer Science},
year = {2016},
month = {February},
location = {Innsbruck, Austria},
school = {University of Innsbruck},
type = {PhD Thesis (Dissertation)}
}


## Technical reports and local workshops

1. , “A Joint Network/Control Design for Cooperative Automatic Driving: Extended Version”, DISI, University of Trento, Italy, Technical Report DISI-17-012, Aug. 2017. [BibTeX file, PDF]
@techreport{giordano2017joint-tr,
author = {Giordano, Giulia and Segata, Michele and Blanchini, Franco and Lo Cigno, Renato},
title = {{A Joint Network/Control Design for Cooperative Automatic Driving: Extended Version}},
year = {2017},
month = {August},
institution = {DISI, University of Trento, Italy},
number = {DISI-17-012},
type = {Technical Report}
}

Cooperative automatic driving, or platooning, is a promising solution to improve traffic safety, while reducing congestion and pollution. The design of a control system for this application is a challenging, multi-disciplinary problem, as cooperation between vehicles is obtained through wireless communication. So far, control and network issues of platooning have been investigated separately. In this work we design a cooperative driving system from a joint network and control perspective, determining worst-case upper bounds on the safety distance subject to network losses, so the actual inter-vehicle gap can be tuned depending on vehicle or network performance. By means of simulation, we show that the system is very robust to packet losses and that the derived bounds are never violated.
2. , “A Modular Approach to Platooning Maneuvers”, in 2nd GI/ITG KuVS Fachgespräch Inter-Vehicle Communication (FG-IVC 2014), Luxembourg City, Luxembourg, Feb. 2014. [BibTeX file, PDF]
@inproceedings{segata2014modular,
author = {Segata, Michele and Dressler, Falko and Lo Cigno, Renato},
title = {{A Modular Approach to Platooning Maneuvers}},
booktitle = {2nd GI/ITG KuVS Fachgespr{\"{a}}ch Inter-Vehicle Communication (FG-IVC 2014)},
year = {2014},
month = {February},
i7peerreview = {no}
}

Driving vehicles in platoons has the potential to improve traffic efficiency, increase safety, reduce fuel consumption, and make driving experience more enjoyable. A lot of effort is being spent in the development of technologies, like radars, enabling automated cruise control following and ensuring emergency braking if the driver does not react in time; but these technologies alone do not empower real platooning. As platoons will initially share the road with human-driven vehicles, interesting new questions regarding the interactions between the two categories of vehicles arise. In this paper we briefly describe the focus of our research, i.e., the analysis of interferences caused by non-automated vehicles during a maneuver. As an example, we consider the JOIN maneuver. We define the application layer protocol to support the maneuver, together with situations that can prevent successful termination, and describe how they can be detected. We then show the validity of the idea by simulating some sample scenarios, showing either that the maneuver can successfully be performed, or safely be aborted. As final contribution, we describe our idea toward a modular approach, i.e., the development of complex maneuvers by combining smaller sub-maneuvers, aiming to ease development and safety analysis.
3. , “Novel Communication Strategies for Platooning and their Simulative Performance Analysis”, in 1st GI/ITG KuVS Fachgespräch Inter-Vehicle Communication (FG-IVC 2013), Innsbruck, Austria, Feb. 2013. [BibTeX file, PDF]
@inproceedings{segata2013novel,
author = {Segata, Michele},
title = {{Novel Communication Strategies for Platooning and their Simulative Performance Analysis}},
booktitle = {1st GI/ITG KuVS Fachgespr{\"{a}}ch Inter-Vehicle Communication (FG-IVC 2013)},
year = {2013},
month = {February},
i7peerreview = {no}
}

Platooning, the act of a car autonomously following its leaders to form a road train, is a hot topic in research. It has the potential to improve traffic flow on freeways, improve safety, and enhance the driving experience. A lot of effort has been put in several projects in order to implement and test systems capable of performing close car following. While the problems related to control theory seems to be solved, some questions regarding communication are still open. Wireless networking is fundamental for this application, as it is needed to manage and maintain the platoons and, clearly, has strict requirements in terms of frequency update and delay constraints. This paper surveys the literature about platooning systems and related research, identifies some open challenges, presents a simulation framework which can be used to tackle them, and outlines promising approaches.
4. , “An IEEE 802.11a/g/p OFDM Receiver for GNU Radio”, University of Innsbruck, Institute of Computer Science, Technical Report CCS-2013-02, Mar. 2013. [BibTeX file, PDF]
@techreport{bloessl2013ofdm-tr,
author = {Bloessl, Bastian and Segata, Michele and Sommer, Christoph and Dressler, Falko},
year = {2013},
month = {March},
institution = {University of Innsbruck, Institute of Computer Science},
number = {CCS-2013-02},
type = {Technical Report}
}

@techreport{segata2013shadowing,
`