Prof. Dr. Wolfgang König

Executive Board Member

Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS) / TU Berlin
Mohrenstr. 39
10117 Berlin
+49 (0) 30 +49 (0)30 20372-547
koenig@wias-berlin.de
Website


Research focus

probability theory
statistical mechanics
stochastic models in telecommunication

Projects as a project leader

  • CH-AP26

    Branching random walks in random environment with a special focus on the intermittent behavior of the particle flow

    Prof. Dr. Wolfgang König

    Project heads: Prof. Dr. Wolfgang König
    Project members: -
    Duration: 01.04.2013 - 31.08.2016
    Status: completed
    Located at: Weierstraß-Institut

    Description

    We study the long-time behaviour of branching random walk in random environment (BRWRE) on the d-dimensional lattice. We consider one of the basic models, which includes migration and branching/killing of the particles, given a random potential of spatially dependent branching/killing rates. Based on the observation that the expectation of the population size over the migration and the branching and killing is equal to the solution to the well-known and much-studied parabolic Anderson model (PAM), we will use our understanding of the long-time behaviour of the PAM to develop a detailed picture of the BRWRE. Furthermore, we will exploit methods that were successful in the treatment of the PAM to prove at least part of this picture. Particular attention is payed to the study of the concentration of the population in sites that determine the long-time behaviour of the PAM, which shows a kind of intermittency. One fundamental thesis that we want to make precise and rigorous is that the overwhelming contribution to the total population size of the BRWRE comes from small islands where most of the particles travel to and have a extremely high reproduction activity. We aim at a detailed analysis for the case of the random potential being Pareto-distributed, in which case the rigorous study of the PAM has achieved a particularly clear picture. This project has the following four main goals. I. For a variety of random potentials, we derive large-time asymptotics for the n-th moments of the local and total population size, based on techniques from the study of the PAM. II. We want to understand and identify the limiting distributions of the global population size by a finer analysis for Pareto-distributed potentials. III. We want to investigate, for Pareto-distributed potentials, the long-time (de)correlation properties of the evolution of the particles such as aging, in particular, slow/fast evolution phenomena and what type of aging functions will appear. IV. We want to study, for Paretodistributed potentials, almost surely with respect to the potential, the particle flow of the BRWRE in a geometric sense by finding trajectories along which most of the particles travel and branch, in particular the sites and the time intervals where, respectively when, most of the particles show an extremely high reproduction activity.

    http://www.dfg-spp1590.de/abstracts.php#34
  • MI11

    Data mobility in ad-hoc networks: Vulnerability & security

    Dr. Benedikt Jahnel / Prof. Dr. Wolfgang König

    Project heads: Dr. Benedikt Jahnel / Prof. Dr. Wolfgang König
    Project members: Alexander Wapenhans
    Duration: -
    Status: running
    Located at: Weierstraß-Institut

    Description

    Present day telecommunication networks are ill equipped for the rapidly growing demand for mobile data transfers. With the fifth generation of mobile networks, paradigmatic shifts in the design of the network are on the agenda. A critical aspect here is the role of infrastructure. Multilayered cellular networks with possible incorporation of relaying mechanisms are under investigation not only in the scientific community, but also in industry. All these new designs have in common a rapid increase of degrees of freedom in the system. The central role of (expensive) base stations is reduced in favour of an increasingly important role of (cheap) relays. In particular, also the users of the system will be attached a relay functionality in the system. As a result, the network becomes more and more decentralised. First implementations of peer-to-peer (P2P) communications for public use are already available. Exploring the possible benefits of such new architectures is in full swing in the academic and the industrial research. For a survey on device-to-device (D2D) communication in cellular networks see for example. One promising way to cope with the new and more complex structures that arise is to exploit probabilistic methods. Indeed, fundamental ansatzes from stochastic geometry (e.g., spatial Poisson processes, continuum percolation theory, ...) are widely used for modelling the spatial locations of the users, the relays and the base stations and their basic connectivity properties. For the description of temporal developments, standard methods from stochastic processes (stochastic interacting particle processes like bootstrap percolation or the contact process) are commonly used to model the spread of information through a network. Of crucial importance in all these future scenarios with less centralised architectures is a good understanding of vulnerability and security, in particular of the way in which malware (e.g., proximity-based propagation sabotage software or computer killing viruses like Cabir or CommWarrior) spreads in such networks. For usual networks, a number of strategies have been exploited by operators in order to restrict the spread of the malware and to keep the functionality of the network available. For security in D2D communication networks see the review. However, the new challenges accompanying the system decentralisation also include the question how successful these defense strategies can be in such systems, in particular since the spread of malware (more generally, of any information) in such a system follows a different set of rules than in centralised networks. The project aims at a probabilistic analysis of (1) the velocity of the propagation of infected or otherwise flawed relays in a realistic mobile ad-hoc network if a malware has attacked some node(s), and (2) of the performance and the success of some of the most widely used security strategies against this.

    http://www.wias-berlin.de/people/koenig/?lang=0 http://www.wias-berlin.de/people/jahnel/?lang=0
  • MI-AP3

    Probabilistic methods for ad-hoc networks with mobile relays

    Prof. Dr. Wolfgang König

    Project heads: Prof. Dr. Wolfgang König
    Project members: -
    Duration: 01.09.2014 - 31.08.2017
    Status: running
    Located at: Weierstraß-Institut

    Description

    The latest LTE-Advanced standard introduces fixed relays to reduce the number of base stations (substantially reducing costs) and improve service quality. The relay concept is extended to include users' devices as mobile relays, to further strengthen these benefits. The impact of mobile relays strongly depends on the environment (number of users, their locations and mobility). We investigate a a novel combination of rigorous probability theory and simulation-based systems engineering to study the benefits of this new concept for network operators.

    http://www.wias-berlin.de/research/lgs/lg4/index.jsp?lang=1