Showing papers by "Gyorgy Dan published in 2008"

Cooperative caching and relaying strategies for peer-to-peer content delivery

Abstract: Peer-to-peer content distribution has become a major source of bandwidth costs for Internet service providers (ISPs) One way for ISPs to decrease these costs is to deploy caches for p2p traffic To make efficient use of the caches, in this paper we propose a cooperative caching and relaying scheme that is compatible with the existing business relations between ISPs We formulate the problem of cooperative caches as a resource allocation problem, and show that it is related to the problem of r-configuration studied in graph theory We propose a distributed algorithm to solve the resource allocation problem, and show that cooperation leads to significant gains compared to non-cooperative caching

Delay bounds and scalability for overlay multicast

Abstract: A large number of peer-to-peer streaming systems has been proposed and deployed in recent years. Yet, there is no clear understanding of how these systems scale and how multi-path and multihop transmission, properties of all recent systems, affect the quality experienced by the peers. In this paper we present an analytical study that considers the relationship between delay and loss for general overlays: we study the trade-off between the playback delay and the probability of missing a packet and we derive bounds on the scalability of the systems. We use an exact model of push-based overlays to show that the bounds hold under diverse conditions: in the presence of errors, under node churn, and when using forward error correction and various retransmission schemes.

Robust source-channel coding for real-time multimedia

Abstract: Multimedia applications operating in today's Internet have to employ some form of error resilience to cope with losses. For interactive applications with strict delay constraints the latency introduced by these schemes has to be low as well. Furthermore the parameters of the applied scheme have to be set based on measurements in a possibly rapidly changing environment. In this paper we propose a robust method, called min---max-?, for optimal source-channel code rate allocation to deal with time-varying packet channels and channel state estimation errors. We evaluate its performance when used with forward error correction and multiple description coding in both stationary and non-stationary environments. We show that on a stationary channel robust rate allocation is suboptimal in terms of mean distortion, but it achieves a lower variance, while on a non-stationary channel it prevents severe degradation of the quality. We apply the proposed rate allocation method to motion compensated video and show that it performs better on a non-stationary channel than minimization of the mean distortion proposed earlier.