Károly Farkas

Crowdsending based public transport information service in smart cities

Thanks to the development of technology and the emergence of intelligent services smart cities promise to their inhabitants enhanced perception of city life. For example, a live timetable service of public transportation can increase the efficiency of travel planning substantially. However, its implementation in a traditional way requires the deployment of some costly sensing and tracking infrastructure. Mobile crowdsensing is an alternative, when the crowd of passengers and their mobile devices are used to gather data for almost free of charge. In this paper, we put the emphasis on the introduction of our crowdsensing based public transport information service, what we have been developing as a prototype smart city application. The front-end interface of this service is called TrafficInfo. It is a simple and easy-to-use Android application which visualizes real-time public transport information of the given city on Google Maps. The lively updates of transport schedule information relies on the automatic stop event detection of public transport vehicles. TrafficInfo is built upon our Extensible Messaging and Presence Protocol (XMPP) based communication framework what we designed to facilitate the development of crowd assisted smart city applications. The paper introduces shortly this framework, than describes TrafficInfo in detail together with the developed stop event detector.

Motivations, design and business models of wireless community networks

In this paper we provide an integrated presentation of applications, technologies and business models for wireless community network together with design considerations and examples. An overview is given of the state-of-the-affairs of wireless community networks. Driving forces and stakeholders of the projects and the applications and services will be presented for some carefully selected cases. We suggest a design methodology and illustrate its application to an ongoing digital city project in Hungary. Relevant business models are also analyzed.

A Mean Field Based Methodology for Modeling Mobility in Ad Hoc Networks

In this paper we propose a methodology for the modeling and analysis of ad hoc networks composed by a large number of nodes moving among geographical regions. This methodology uses compositional construction of stochastic Petri nets (SPN) for building the model which allows for specifying the model and the required performance indices at a high level of abstraction. As our aim is to consider real scenarios with several geographical regions and non-trivial user behavior in each region, the size of the state space of the model can easily grow too large to analyze with exact analytical approaches or even with simulation. For this reason, we propose to carry out the analysis by constructing the mean field approximation of the behavior of the SPN. The approximation is provided by a set of ordinary differential equations (ODE) that can be derived automatically from the SPN and can be solved numerically with low computational effort even for large models. The methodology is illustrated on a case study, modeling application spreading in a mobile environment. It will be shown that the approximate results obtained by the mean field approach capture well the behavior of the system.

Advances in wireless mesh networks

Wireless mesh networks facilitate the extension of wireless local area networks into wide areas and have emerged as a promising approach for future network accesses. Prior efforts on wireless networks, especially multi-hop ad hoc networks, have led to significant research contributions that range from fundamental results on theoretical capacity bounds to numerous practical routing and transport protocols. Unlike ad hoc networks, however, mesh networks can serve as access networks that employ multi-hop wireless forwarding by fixed mesh nodes to relay traffic to and from the wired Internet. The unique features of wireless mesh networks pose challenges in designing affordable, reliable, and sustainable network infrastructures. The critical issues span a rich spectrum of issues from interference-aware channel assignment, multi-hop routing, to reliable transport and infrastructure optimization, many of which have to be revisited in this new context. The purpose of this special issue is to archive the stateof-the-art achievements in wireless mesh networking. We received 30 original and unpublished research papers in both theoretical studies and practical protocol/architecture designs for wireless mesh networks, as well as prototypes. All these papers have gone through a strict peer review process, and among them, 14 high quality papers were selected, which offer a broad and updated coverage of wireless mesh network research and development. In addition, two high-quality papers selected from The Third International Wireless Internet Conference (WICON’2007) are included in this special issue as well. The first two papers of the special issue deal with quality of service (QoS) issue in wireless mesh networks. The paper “Provisioning of Parameterized Quality of Service in 802.11e Based Wireless Mesh Networks,” by Xiaowen Chu, presents a framework for the provisioning of parameterized QoS in 802.11e based wireless mesh networks. By enforcing admission control algorithms and scheduling algorithms, this framework can support constant bit-rate (CBR) and variable bit-rate (VBR) traffic flows. Deterministic endto-end delay bounds for CBR traffic flows and VBR traffic flows that conform to leaky-bucket regulators have been derived. For VBR traffic flows without leaky-bucket regulators, a dynamic transmission opportunity (TXOP) scheduling algorithm has been proposed which was shown to be very effective in achieving high channel utilization ratio while keeping an acceptable delay performance. The paper entitled “QoS Differentiation for IEEE 802.16 WiMax Mesh Networks,” by Yan Zhang, Honglin Hu, and HsiaoMobile Netw Appl (2008) 13:1–5 DOI 10.1007/s11036-008-0055-3

Motivations, technologies, and sustainability models of wireless municipal networks

In this article we provide an integrated presentation of applications, technologies, and business models for wireless municipal networks together with design considerations. We give an overview on the state of affairs in municipal networks, presenting the driving forces and stakeholders of these projects, the applications and services for some carefully selected cases, and the available wireless technologies and regulatory issues. Then we outline the design methodology to build wireless municipal networks, presenting a pilot municipal network in Hungary, and discuss the relevant sustainability and business models, which are analyzed and illustrated by summaries of case studies.

Comparison of Service Management Architectures in MANETs

Service management in mobile ad hoc networks is a challenging task due to the inherent properties of such networks (eg., lack of central infrastructure, error-prone wireless connections, limited resources). Traditional management architectures follow either the centralized client/server or the distributed peer-to-peer model. The former shows low fault tolerance since the latter suffers from limited scalability. As a compromise, a hybrid, zone-based architecture can offer solutions for these shortcomings.In this paper, we compare the zone-based architecture to the client/server and peer-to-peer approaches. To select the zone servers and maintain the zones we use our previously developed algorithm called PBS. Via simulations we show how the zone-based architecture over performs the other approaches in the sense of fault tolerance and scalability.