Ádám Horváth

Survey Secure and reliable clustering in wireless sensor networks: A critical survey

In the past few years, research interest has been increased towards wireless sensor networks (WSNs) and their application in both the military and civil domains. To support scalability in WSNs and increase network lifetime, nodes are often grouped into disjoint clusters. However, secure and reliable clustering, which is critical in WSNs deployed in hostile environments, has gained modest attention so far or has been limited only to fault tolerance. In this paper, we review the state-of-the-art of clustering protocols in WSNs with special emphasis on security and reliability issues. First, we define a taxonomy of security and reliability for cluster head election and clustering in WSNs. Then, we describe and analyze the most relevant secure and reliable clustering protocols. Finally, we propose countermeasures against typical attacks and show how they improve the discussed protocols.

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.

Usability of Deterministic and Stochastic Petri Nets in the Wood Industry: A Case Study

Deterministic and stochastic Petri nets (DSPNs) are commonly used for modeling processes having either deterministically, or exponentially distributed delays. However, DSPNs are not widespread in the wood industry, where the leaders of a company try to make decisions based on common sense instead of using high-level performance evaluation methods.

A finite-source queuing model for spectrum renting in mobile cellular networks

Nowadays, spectrum renting is a frequently investigated research topic with the aim of improving the efficiency of spectrum usage in mobile cellular networks. In this paper, we propose a finite-source queuing model, in which service providers may rent each others unutilized frequency bands. Our model contains two source pools: one for subscribers generating fresh calls in the investigated mobile cell, and another for modeling handover calls. The model considers the traveling of subscribers over the borders of the investigated mobile cell, too. Moreover, we take into account the retrial phenomenon caused by the impatience of subscribers.

TiPeNeSS: a timed petri net simulator software with generally distributed firing delays

Performance analysis can be carried out in several ways, especially in case of Markovian models. In order to interpret high level of abstraction, we often use modeling tools like timed Petri nets (TPNs). Although some subclasses of TPNs (e.g. stochastic Petri nets (SPNs) [17, 19]) can be handled analytically, a general timed Petri net is hard to evaluate via numerical analysis. However, the simulation of SPNs or deterministic and stochastic Petri nets (DSPNs) [16] are supported by many known tools (see, e.g. [3, 20]), it is hard to find a simulation tool for timed Petri nets with generally distributed (i.e., particular but arbitrarily chosen) firing times. In this paper, we present TiPeNeSS (Timed Petri Net Simulator Software) which supports the simulation of timed Petri nets containing transitions with generally distributed firing delays. The input of the software (the Petri net and the parameters) is defined in an XML file, what allows us to generate results in batch mode. Besides, we describe a case study in which we optimize the frequency of the regular maintenance in a manufacturing process.

Modelling opportunistic spectrum renting in mobile cellular networks

Spectrum pooling enables the opportunistic usage of licensed frequency bands for secondary users during the idle periods of primary users, which can be applied to relieve temporary bottlenecks in mobile cellular networks. In this paper, we provide an analytical framework for the performance evaluation of the interaction of multiple operators who cooperate and apply an opportunistic spectrum renting scheme. Based on our investigation, we provide a flexible and simple cooperation scheme when more than two operators are involved.