Sabine Wittevrongel

Bio: Sabine Wittevrongel is an academic researcher from Ghent University. The author has contributed to research in topics: Queueing theory & Queue. The author has an hindex of 15, co-authored 220 publications receiving 1215 citations.

Analysis and Modeling of Video Popularity Evolution in Various Online Video Content Systems: Power-Law versus Exponential Decay

Abstract: Internet evolved from a world communication network with restricted information transmission capabilities into an entertainment and information network with many broadband clients and more multimedia-rich applications. In particular, video (streaming) applications are gaining in popularity and usage, but those are also notorious for their high resources demand. A study of the popularity evolution of videos in different online video content systems can give insight and have implications for adequate network dimensioning. In this paper we study and model the popularity evolution of some video traces from YouTube, one Dutch catch-up TV online portal, and historical data on DVD rentals in the US. The model we put forward can degenerate into either a power-law distribution or an exponential distribution depending on its form-determining parameter. We find out that not all traces have a power-law decay as suggested in other works, but also a significant part of those expose an exponential popularity evolution.

A discrete-time priority queue with train arrivals

Abstract: We analyze a discrete-time priority queue with train arrivals. Messages of a variable number of fixed-length packets belonging to two classes arrive to the queue at the rate of one packet per slot. We assume geometrically distributed message lengths. Packets of the first class have transmission priority over the packets of the other class. By using probability generating functions, some performance measures such as the moments of the packet delay are calculated. The impact of the priority scheduling discipline and the correlation in the arrival process is shown by some numerical examples.

Comparison of simulcast and scalable video coding in terms of the required capacity in an IPTV network

Abstract: The diversity of multimedia-enabled devices supporting streamed multimedia is ever growing. Multicast delivery of TV channels in IP networks to a heterogeneous set of clients can be organised in many different ways, which brings up the discussion which one is optimal. Scalable video streaming has been believed to be more efficient in terms of network capacity utilisation than simulcast video delivery because one flow can serve all terminals, while with simulcast all resolutions are offered in parallel. At the same time, it is also largely recognised that in order to provide the same video quality compared to non-layered video coding, scalable video coding (SVC) incurs a bit rate penalty. In this paper we compare simulcast and SVC in terms of their required capacity in an IPTV network scenario where a bouquet of TV channels is offered to the subscribers. We develop methods to calculate and approximate the capacity demand for two different subscriber behaviour models. These methods are then used to explore the influence of various parameters: the SVC bit rate penalty, the number of offered channels, the channel popularity and the number of subscribers. The main contribution of this paper is that we derive an analytical formula to calculate the SVC limit bit rate penalty beyond which SVC is less efficient than simulcast. In the realistic IPTV examples considered here, the limit is found to lie between 16% and 20%, while the reported values for this coding penalty range from 10% up to 30% for current H.264 SVC codecs, indicating that SVC in IPTV is not always more efficient than simulcast.

Applied Probability and Queues

Abstract: (1987). Applied Probability and Queues. Journal of the Operational Research Society: Vol. 38, No. 11, pp. 1095-1096.

Nonlinear Fractional Programming

Abstract: In this chapter we deal with the following nonlinear fractional programming problem: $$P:\mathop{{\max }}\limits_{{x \in s}} q(x) = (f(x) + \alpha )/((x) + \beta )$$ where f, g: R n → R, α, β ∈ R, S ⊆ R n . To simplify things, and without restricting the generality of the problem, it is usually assumed that, g(x) + β + 0 for all x ∈ S,S is non-empty and that the objective function has a finite optimal value.

Boundary value problems

Abstract: Boundary Value Problems in Physics and Engineering By Frank Chorlton. Pp. 250. (Van Nostrand: London, July 1969.) 70s

Optical burst switching (OBS) - a new paradigm for an optical Internet

Abstract: To support bursty traffic on the Internet (and especially WWW) efficiently, optical burst switching (OBS) is proposed as a way to streamline both protocols and hardware in building the future gener...