Nicholas Loulloudes

On the structure and evolution of vehicular networks

Vehicular ad hoc networks have emerged recently as a platform to support intelligent inter-vehicle communication and improve traffic safety and performance. The road-constrained and high mobility of the vehicles, their unbounded power source, and the emergence of roadside wireless infrastructures make VANETs a challenging research topic. A key to the development of protocols for intervehicle communication and services lies in the knowledge of the topological characteristics of the VANET communication graph. This article provides answers to the general question: how does a VANET communication graph look like over time and space? This study is the first one that examines a very large-scale VANET graph and conducts a thorough investigation of its topological characteristics using several metrics, not examined in previous studies. Our work characterizes a VANET graph at the connectivity (link) level, quantifies the notion of “qualitative” nodes as required by routing and dissemination protocols, and examines the existence and evolution of communities (dense clusters of vehicles) in the VANET. Several latent facts about the VANET graph are revealed and incentives for their exploitation in protocol design are examined.

Information Dissemination in Mobile CDNs

With the recent development of technologies in wireless access and mobile devices, the mobile network has become a key component of today’s Internet vision [1, 46]. Current mobile networks, which are being deployed worldwide, enable mobility features to new applications and also extend existing wired Web applications to mobile terminals. The mobile wireless network offers a rich assortment of dynamic and interactive services, such as GPS navigation information, mobile TV, vehicular traffic information, and location-oriented services. The provision of such services requires techniques to disseminate data as efficiently as possible in order to minimize the total network traffic and to improve the mean response time to mobile users. In the wired Web, network performance can be substantially enhanced by using additional bandwidth, which is often available at low cost. However, this approach is impractical for mobile wireless network infrastructures. Most of these networks have fixed spectrum and achievable data rate is fundamentally limited by interference [46]. This problem is likely to get more serious when more mobile users start using bandwidth-intensive services such as streaming media. In this context, caching and prefetching might be a solution. Specifically, these approaches have been extensively used in the wired Web to optimize the amount of bandwidth consumption by shifting the traffic away from overloaded content providers and closer to the content customers [43]. Although these methods offer several benefits (i.e. conservation of network resources and reduced latency), the dissemination of dynamic content and resource-hungry applications (e.g. multimedia applications) remain a challenge.

Managing and Monitoring Elastic Cloud Applications

Next generation Cloud applications present elastic features and rapidly scale their comprised resources. Consequently, managing and monitoring Cloud applications is becoming a challenge. This paper showcases the functionality and novel features of: (i) c-Eclipse, a framework for describing Cloud applications along with their elasticity requirements and deploying them on any IaaS provider; and (ii) JCatascopia, a fully-automated, multi-layer, interoperable Cloud monitoring system. Particularly, we demonstrate how a user can manage the full lifecycle of a three-tier web application and observe, in real-time, how an elasticity management platform automatically scales the application based on various user-defined elasticity requirements, workloads and performance metrics.

On the Evaluation of Caching in Vehicular Information Systems

VANETs have been envisioned as an infrastructure for deploying Vehicular Information Systems (VIS) that among others provide drivers with an up-to-date view on the prevailing traffic conditions. In this work we evaluate the benefits of caching vehicular information obtained from such VIS through VITP, a location-aware, application-layer communication protocol that we extend to support caching. We present an evaluation study of our approach conducting extensive simulation on large scale vehicular networks under different realistic urban traffic conditions Our results identify the critical parameters that affect information quality in VANETs as well as demonstrate the viability and effectiveness of the cache-enabled VITP.

Enabling Interoperable Cloud Application Management through an Open Source Ecosystem

Cloud computing enables on-demand provisioning of computing resources to IT solutions, following a utility-based approach. Technology and standardization developments in traditional public utilities enable customers to seamlessly migrate across utility providers without being required to make changes to their home appliances. Dubbed as the fifth utility, cloud computing customers should have user-friendly tools and mechanisms at their disposal, which preserve application deployments across different resource providers. Here, the authors present current efforts to develop an open source Cloud Application Management Framework (CAMF) based on the Eclipse Rich Client Platform. This framework facilitates cloud application lifecycle management in a vendor-neutral approach.

c-Eclipse: An Open-Source Management Framework for Cloud Applications

Cloud application portability and optimal resource allocation are of great importance in the realm of Cloud infrastructure provisioning. c-Eclipse is an open-source Cloud Application Management Framework through which users are able to define the description, deployment and management phases of their Cloud applications in a clean and intuitive graphical manner. It is built on top of the well-established Eclipse platform and it adheres to two highly desirable features of Cloud applications: portability and elasticity. In particular, c-Eclipse implements the open, non-proprietary OASIS TOSCA specification for describing the provision, deployment and re-contextualization of applications across different Cloud infrastructures, thereby ensuring application portability. Furthermore, c-Eclipse enables Cloud users to specify elasticity policies that describe how the deployed virtualized resources must be elastically adapted at runtime to match the needs of a dynamic application-workload. In this paper, we introduce the architecture and implementation of c-Eclipse, and describe its key characteristics via a use-case scenario that involves a user creating a description of a 3-tier Cloud application, enriching it with appropriate elasticity policies, submitting it for deployment to two different Cloud providers and, finally, monitoring its execution.

On the performance evaluation of VANET routing protocols in large-scale urban environments (Poster)

With the increasing capabilities of vehicular communications technology, VANETs (Vehicular Ad-Hoc Networks) have witnessed a significant development. Key to the establishment of value-added services and applications is the design and development of routing protocols. This article studies the effects that mobility, road topology and network applications have on the performance evaluation of VANET routing protocols. Specifically, we evaluate the performance of three known and highly established VANET routing protocols by employing realistic mobility from a large-scale urban topology and imposing network load via an exemplary VANET-based, traffic query, application. We compare the results against results obtained by following the simplistic evaluation approaches often available in the literature. We argue that results stemming from such a realistic evaluation approach, increase the possibility of identifying problems as well as implications in the design of routing protocols that need to be considered and addressed for achieving optimal performance.

Caching dynamic information in vehicular ad hoc networks

Recent advances in VANET technologies have propelled the development and deployment of a wide variety of Vehicular Information Systems (VIS) to vehicles. Such systems provide real-time, crucial information, to drivers, ranging from collision avoidance warnings to the availability of road-side facilities. Despite the invaluable information provided by such systems, the imposed network overhead, due to the necessity of maintaining a global view of the road/vehicular networks and the surrounding environment, cannot be dismissed. In this work we evaluate the performance of VIS when utilizing caching techniques as means of minimizing network overhead. We present an evaluation study of our approach by conducting extensive simulations on large-scale vehicular networks under different realistic urban traffic conditions. Our evaluation results identify the critical parameters that affect information quality in VANETs as well as demonstrate the viability and effectiveness of the cache-enabled VITP.

V-Radar: A vehicular traffic query protocol for urban environments

Automobile congestions have an adverse effect in modern societies, causing the loss of billions of dollars and manhours every year throughout the world. In this era of global economic recession, drivers will require the necessary solutions and driving aids that facilitate the improvement of daily road transport and minimize unnecessary expenditure. In this work, we lay the groundwork for V-Radar, a query protocol for retrieving vehicular traffic information using V2V communications. The advantage of V-Radar over related works is its ability to monitor using location-dependent queries the prevailing traffic conditions in a number of road-paths from a vehicles current location towards its final destination. We introduce its modular architecture and provide preliminary evaluation results showing significant improvements over a similar scheme.

Enabling cloud application portability

The Cloud Application Management Framework (CAMF) enables Cloud application developers to design, deploy and manage their applications through an intuitive blueprint design. In this paper we show how Cloud application developers can utilize CAMF in order to have portable applications that can be deployed on different IaaS with minimal effort. Towards this goal, we introduce the Cloud Application Requirement Language (CARL). CARL can be used for defining the application software and hardware requirements, information that is then included into the TOSCA description of the Cloud application, alongside the application blueprint. CAMFs Information Service utilizes both these artifacts to provide IaaS specific configurations that fulfill the users requirements.