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PEOPLE@HES-SO – Directory and Skills inventory

PEOPLE@HES-SO
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Riedi Rudolf

Riedi Rudolf

Ordentlicher Professor FH

Main skills

Wahrscheinlichkeit und Statistik

Signal Processing (Images/Video)

TCP Modelling / Ad hoc Networking

Fractals / Multifractals / Scaling

  • Contact

  • Teaching

  • Research

  • Publications

Main contract

Ordentlicher Professor FH

Phone: +41 26 429 67 61

Desktop: HEIA_D30.19

Haute école d'ingénierie et d'architecture de Fribourg
Boulevard de Pérolles 80, 1700 Fribourg, CH
HEIA-FR
Institute
iSIS - Institut des systèmes intelligents et sécurisés
BSc HES-SO en Télécommunications - Haute école d'ingénierie et d'architecture de Fribourg
  • Traitement d'images et des videos
  • Cryptographie (Théorie)
  • Ad hoc networking
  • TCP traffic modelling and estimation

Completed

Stockage intelligent de séries temporelles à l'aide de caching prédictif
AGP

Role: Co-applicant

Requérant(e)s: IICT, Robert Stephan, IICT

Financement: HES-SO Rectorat

Description du projet : Nous proposons une nouvelle méthode, appelée PICASSO (PredICtive cAching framework for faSt temporal StOrage), pour augmenter les performances des solutions de stockage au niveau matériel et logiciel, pour de très grands volumes de séries temporelles. Nos algorithmes utilisent des modèles qui prévoient l'accès aux données et qui peuvent ainsi diminuer les coûts de stockage de manière drastique. La réduction des coûts va faire profiter à la fois les entreprises et les scientifiques qui ont besoin d'accéder à des séries temporelles de manière efficace.

Research team within HES-SO: Rappos Efstratios , Robert Stephan , Riedi Rudolf

Partenaires académiques: IICT; FR - EIA - Institut iSIS; Robert Stephan, IICT

Durée du projet: 01.09.2011 - 30.04.2013

Montant global du projet: 167'300 CHF

Statut: Completed

Metadata Mining (Analyse et modélisation des métadonnées en utilisant le data mining, démonstrateur d'analyse de logs de téléinformatique en collaboration avec NetGuardians SA)
AGP

Role: Collaborator

Financement: HES-SO Rectorat; IICT; FR - EIA - Institut HumanTech; IICT

Description du projet : Concevoir et implémenter une plate-forme collaborative de gestion et d'analyse de métadonnées générées par l'utilisation du système par des utilisateurs authentifiés, dans le but d'enrichissement, de partage et de validation de métadonnées. En exploitant les métadonnées par des outils de data mining adaptés, les connaissances valides, nouvelles et potentiellement utiles extraites seront mise à disposition des utilisateurs. En classifiant et en regroupant les métadonnées, les processus de recherche et de navigation seront améliorés.

Research team within HES-SO: Dutoit Fabien , Raileanu Laura Elena , Fatemi Nastaran , Sokhn Maria , Riedi Rudolf , Abou Khaled Omar

Durée du projet: 01.06.2009 - 30.09.2012

Montant global du projet: 219'900 CHF

Statut: Completed

2018

Arena Function: A Framework for Computing Capacity Bounds in Wireless Networks
Scientific paper

Riedi Rudolf, Alireza Keshavarz-Haddad

IEEE Transactions on Wireless Communications, 2018 , vol.  17, no  2, pp.  1134-1146

Summary:

Bounds on the capacity of wireless networks often rely on simplifying assumptions and are given in terms of coarse network parameters such as the number of nodes. While useful due to their simplicity such bounds can significantly overestimate the achievable capacity in real world situations, ignoring actual network topology and traffic patterns.
The results of this paper improve such analytical results on network capacity in several ways. At the heart of our methodology lies the concept of transmission arenas which indicate the presence of active transmissions near any given location in the network. This novel space-based approach is well suited to untangle the interactions of simultaneous transmissions. Avoiding a graph-based model of the network it opens new avenues of studying capacities.
For homogeneous networks we recover classical bounds. However, our methodology applies to arbitrary networks and can, thus, inform placing and activating of nodes also in the presence of clustering. Our method works with all classical channel models and dimensions. It provides bounds on the transport capacity which involve only high level knowledge of node locations, such as the length of Euclidean Minimum Spanning Tree. As an additional novelty we establish bounds on wireless unicast and multicast capacities.

2014

Bounds on the Benefit of Network Coding for Wireless Multicast and Unicast
Scientific paper

Riedi Rudolf, Alireza Keshavarz-Haddad

IEEE Transactions on Mobile Computing, 2014 , vol.  13, no  1, pp.  102-115

Summary:

In this work we establish fundamental limitations to the benefit of network coding in terms of energy and throughput in multihop wireless networks. Thereby we adopt two well accepted scenarios in the field: single multicast session and multiple unicast sessions. Most of our results apply to arbitrary wireless network and are, in particular, not asymptotic in kind.
In terms of throughput and energy saving we prove that the gain of network coding of a single multicast session is at most a constant factor. Also, we present a lower bound on the expected number of transmissions of multiple unicast sessions under an arbitrary network coding. We identify scenarios for which the network coding gain for energy saving becomes surprisingly close to 1, in some cases even exactly 1, corresponding to no benefit at all. Interestingly, we prove that the gain of network coding in terms of transport capacity is bounded by a constant factor pi in any arbitrary wireless network and for all traditional channel models. This shows that the traditional bounds on the transport capacity do not change more than constant factor pi if we employ network coding. As a corollary, we find that the gain of network coding on the throughput of large scale homogeneous wireless networks is asymptotically bounded by a constant. Note that our result is more general than the previous work and it is obtained by a different technique. In conclusion, we show that in contrast to wired networks, the network coding gain in wireless networks is constraint by fundamental limitations.

2013

Brownian Motion
Scientific paper

Riedi Rudolf

Encyclopedia of Environmetrics, A.-H. El-Shaarawi and W. Piegorsch (eds), John Wiley & Sons Ltd: Chichester, UK., 2013 , vol.  online Encyclopedia at Wiley Online Library

Link to the publication

Summary:

This article on Brownian motion starts with a short historical survey on its discovery and importance and continues with its most relevant properties. Mathematically detailed formulas are given and connections between the properties are indicated, however no derivations or proofs are provided.

The properties covered start with the mathematical modeling of Brownian motion via the Wiener process; equivalent definitions and constructions such as the Lévy characterization, the midpoint displacement and the re-scaled random walks are discussed. Basic properties given include uniqueness, symmetry, restarted Brownian motion, and time inversion. More advanced topics treated cover stopping times, the strong Markov property, the reflection principle, extreme values, escape times from a strip, and last visits. Discussed are also path oscillations, stationarity, Gaussian white noise, and Karhunen-Löwe expansions. Briefly mentioned are the Brownian motion with drift, the Brownian bridge, as well as intersections, recurrence and transience of Brownian motion in higher dimensions.

Cascades Infiniment Divisibles
Scientific paper
Dans: numéro spécial "Benoît Mandelbrot, Père de la géométrie fractale"

Riedi Rudolf

Gazette des Mathématiciens (Soc. Math. France), 2013 , vol.  136, pp.  119-128

Summary:

L'objectif de cette contribution est de relier les méthodes de travail particulières et le génie innovateur de Benoît Mandelbrot. Le contexte choisi est le développement récent des cascades infiniment divisibles qui a été fortement influencé par Mandelbrot et qui a aidé à construire des ponts entre les domaines de la théorie multifractale et les processus stochastiques.

2010

Multifractal Analysis of Infinite Products of Stationary Jump Processes
Scientific paper
Article ID 807491

Riedi Rudolf

Journal of Probability and Statistics, 2010 , vol.  2010

Link to the publication

Summary:

There has been growing interest in constructing stationary measures with known multifractal properties. In an earlier paper, the authors introduced the multifractal products of stochastic processes (MPSP) and provided basic properties concerning convergence, non-degeneracy and scaling of moments. This paper considers a subclass of MPSP, termed multifractal jump process (MJP), which is determined by jump processes with i.i.d. exponentially distributed interjump times. In this paper, the information dimension and a multifractal spectrum of the MJP are computed. As a side result it is shown that the random partitions imprinted naturally by the Poisson arrivals are sufficient to determine the spectrum in this case.

2003

pathChirp: Efficient Available Bandwidth Estimation for Network Paths
Scientific paper
Best Student Paper Award

Riedi Rudolf, Vinay Ribeiro, Richard Baraniuk, Les Cottrell, Jiri Navratil

Proceedings Workshop on Passive and Active Measurement PAM2003, March 2003, 2003

Link to the publication

Summary:

This paper presents pathChirp, a new active probing tool for estimating the available bandwidth on a communication network path. Based on the concept of ``self-induced congestion,'' pathChirp features an exponential flight pattern of probes we call a chirp. Packet chips offer several significant advantages over current probing schemes based on packet pairs or packet trains. By rapidly increasing the probing rate within each chirp, pathChirp obtains a rich set of information from which to dynamically estimate the available bandwidth. Since it uses only packet interarrival times for estimation, pathChirp does not require synchronous nor highly stable clocks at the sender and receiver. We test pathChirp with simulations and Internet experiments and find that it provides good estimates of the available bandwidth while using only a fraction of the number of probe bytes that current state-of-the-art techniques use.
Keywords: probing, networks, bandwidth, available bandwidth, chirp, end-to-end, inference

2002

Multifractal Processes
Scientific paper
Book Chapter

Riedi Rudolf

Long range dependence : theory and applications eds. Doukhan, Oppenheim and Taqqu, (Birkhäuse) ISBN: 0817641688, 2002 , pp.  625-715

Link to the publication

Summary:

Multifractal theory up to date has been concerned mostly with random and deterministic singular measures, with the notable exception of fractional Brownian motion and Lévy motion. Real world problems involved with the estimation of the singularity structure of both, measures and processes, has revealed the need to broaden the known `multifractal formalism' to include more sophisticated tools such as wavelets. Moreover, the pool of models available at present shows a gap between `classical' multifractal measures, i.e.\ cascades in all variations with rich scaling properties, and stochastic processes with nice statistical properties such as stationarity of increments, Gaussian marginals, and long-range dependence but with degenerate scaling characteristics.
This paper has two objectives, then. For one it develops the multifractal formalism in a context suitable for functions and processes. Second, it introduces truly multifractal processes, building a bridge between multifractal cascades and self-similar processes.
Keywords: Multifractal analysis, self-similar processes, fractional Brownian motion, Lévy flights, stable motion, wavelets, long-range dependence, multifractal subordinator.

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