Michal Piorkowski

TraNS: realistic joint traffic and network simulator for VANETs

Realistic simulation is a necessary tool for the proper evaluation of newly developed protocols for Vehicular Ad Hoc Networks (VANETs). Several recent efforts focus on achieving this goal. Yet, to this date, none of the proposed solutions fulfil all the requirements of the VANET environment. This is so mainly because road traffic and communication network simulators evolve in disjoint research communities. We are developing TraNS, an open-source simulation environment, as a step towards bridging this gap. This short paper describes the TraNS architecture and our ongoing development efforts.

A parsimonious model of mobile partitioned networks with clustering

Mobile wireless networks frequently possess, at the same time, both dense and sparse regions of connectivity; for example, due to a heterogeneous node distribution or radio propagation environment. This paper is about modeling both the mobility and the formation of clusters in such networks, where nodes are concentrated in clusters of dense connectivity, interspersed with sparse connectivity. Uniformly dense and sparse networks have been extensively studied in the past, but not much attention has been devoted to clustered networks.

Island Hopping: Efficient Mobility-Assisted Forwarding in Partitioned Networks

Mobile wireless ad hoc and sensor networks can be permanently partitioned in many interesting scenarios. This implies that instantaneous end-to-end routes do not exist. Nevertheless, when nodes are mobile, it is possible to forward messages to their destinations through mobility. We observe that in many practical settings, spatial node distributions are very heterogeneous and possess concentration points of high node density. The locations of these concentration points and the flow of nodes between them tend to be stable over time. This motivates a novel mobility model, where nodes move randomly between stable islands of connectivity, where they are likely to encounter other nodes, while connectivity is very limited outside these islands. Our goal is to exploit such a stable topology of concentration points by developing algorithms that allow nodes to collaborate to discover this topology and to use it for efficient mobility forwarding. We achieve this without any external signals to nodes, such as geographic positions or fixed beacons; instead, we rely only on the evolution of the set of neighbors of each node. We propose an algorithm for this collaborative graph discovery problem and show that the inferred topology can greatly improve the efficiency of mobility forwarding. Using both synthetic and data-driven mobility models we show through simulations that our approach achieves end-to-end delays comparable to those of epidemic approaches, while requiring a significantly lower transmission overhead

Sampling urban mobility through on-line repositories of GPS tracks

We analyze urban mobility by relying on the short-term mobility traces gathered from a publicly available web-based repository of GPS tracks - the Nokia Sports Tracker service. All mobility traces are obtained from a set of kml files. We show how the data collected voluntarily by individuals, equipped with GPS-enabled mobile phones, can be used to infer accurate, large-scale footprint of urban mobility. This method, unlike others - for example, personal interviewing, is more scalable and less time consuming. It exploits the fact that the on-line masses are willing to share their experience with others. We present a set of heuristics used to filter out bogus tracks from the dataset. We show that the mobility patterns, inferred from the remaining, credible, short-term mobility traces have macroscopic characteristics similar to the characteristics of mobility patterns retrieved from the long-term mobility traces, gathered in different urban environments. The results of our analysis lead to a proposal for creating city-specific mobility profiles. We discuss how such profiles could help improve location privacy and help develop new context-aware applications and services for mobile users.

Mobility-centric geocasting for mobile partitioned networks

We describe our design of a geocast service for mobile partitioned networks (MPNs). We focus mainly on minimizing the delivery latency. Our approach exploits the time-stability of the collective mobility pattern. In MPNs, in contrast to MANETs, the end-to-end path is frequently not available. Thus, communication in such networks becomes problematic. To overcome this difficulty, researchers propose a solution in which the nodepsilas mobility is exploited. This paradigm is often called mobility-assisted forwarding. In order to design routing protocols for MPNs, researchers study key mobility metrics, for example the inter-contact times between nodes. Based on the analysis of a real-life mobility trace, we show that the inter-contact time distribution is spatially dependent. This is a result of spatially heterogeneous mobility pattern that appears to be stable in time. We demonstrate that any georouting protocol designed to work in MPNs can benefit from knowing such an underlying mobility pattern. We propose an abstraction called mobility map that represents the collective mobility pattern. We also present how mobility maps can be used for georouting in MPNs and we also show a simple mechanism for the collaborative discovery of mobility maps. Finally, we propose a geocast protocol for MPNs - GeoMobCast - that explicitly uses mobility maps and is designed to minimize the expected message delay while maximizing the message delivery. We empirically evaluate the protocol by using simulations and we observe the improved performance, compared to other approaches.

Collaborative Transportation Systems

Abstract-We propose a new class of applications for Intelligent Transportation Systems (ITSs), called collaborative transportation applications that aim at solving transportation problems such as congestion and parking. Specifically, we define two applications: SmartPark and SmartRide that leverage short-range wireless communication. We quantify the potential benefits these collaborative transportation applications can offer to an individual and to the public. To this extent, we conduct both the realistic simulations and the analysis of the performance of a taxi cab fleet from San Francisco. Our analysis shows that both collaborative transportation applications can provide with significant savings in travel times, fuel consumptions, etc. Finally, we discuss the functional requirements of collaborative transportation applications and we present the challenges that these applications are facing.