Deutsche Telekom

About: Deutsche Telekom is a company organization based out in Welwyn Garden City, United Kingdom. It is known for research contribution in the topics: Telecommunications network & Signal. The organization has 3473 authors who have published 5208 publications receiving 65429 citations. The organization is also known as: DTAG & German Telecom.

Untersuchung der Lebenszykluskosten von IT-Anwendungen

Abstract: IT management focuses on planning and developing new IT solutions. The importance of production (operation, support, maintenance) and further development of existing solutions is often neglected, although these tasks are responsible for the majority of today’s IT costs. The paper introduces a life cycle model for IT application systems and presents the results of a survey of the life cycle costs of 30 IT application systems. Within the survey, the distribution of costs over the application life cycle was recorded and evaluated. The results show the central importance of recurring costs for production and further development. For a production time of 5 years these costs amounted to 79% of all life cycle costs, whereas only 21% of the costs were incurred during the planning and initial development stages.

Self-stabilizing leader election for single-hop wireless networks despite jamming

Abstract: Electing a leader is a fundamental task in distributed computations. Many coordination problems, such as the access to a shared resource, and the resulting inefficiencies, can be avoided by relying on a leader. This paper presents Select, a leader election protocol for wireless networks where nodes communicate over a shared medium. Select is very robust in two respects. First, the protocol is self-stabilizing in the sense that it converges to a correct solution from any possible initial network state (e.g., where no or multiple nodes consider themselves a leader). This is an appealing property, especially for dynamic networks. Second, the described protocol is resilient against a powerful reactive jammer that blocks a significant fraction of all communication rounds. The reactive model is general and of interest beyond jamming (e.g., in the context of co-existing networks). The paper also reports on experimental results obtained from our simulation framework which allows us to study convergence behavior under different types of adversarial jammers.

Verfahren zur Speicherung oder Übertragung von stereoskopischen Videosignalen

Abstract: Bei einem Verfahren zur Speicherung oder Ubertragung von stereoskopischen Videosignalen, die ein linkes Videosignal und ein rechtes Videosignal enthalten, ist vorgesehen, das das linke und das rechte Videosignal nach einer Vorfilterung unterabgetastet und miteinander nach einem Zeitmultiplexverfahren kombiniert werden, das das kombinierte Signal datenreduzierend codiert und nach der Ubertragung oder Speicherung decodiert wird, das das decodierte kombinierte Signal wieder in ein linkes und ein rechtes Videosignal aufgeteilt wird und das die durch die Unterabtastung verlorenen Abtastwerte durch interpolierte Abtastwerte ersetzt werden. Zur Datenreduktion kommt vorgzugsweise eine Codierung nach dem MPEG-Verfahren in Frage.

TCP-PARIS: a parallel download protocol for replicas

Abstract: Parallel download protocols have the potential to reduce file download time and to achieve a server-side load balancing in replica systems, such as peer-to-peer networks, content distribution networks and mirrored servers, by simultaneously establishing connections to multiple replicas and downloading disjoint file parts in parallel. This paper presents TCP-PARIS, a novel parallel download protocol from multiple replicas to one receiver. Because the ideal partitioning of the transfer volume from each server is a dynamic and a difficult-to-predict function of network conditions, server load and data size, TCP-PARIS uses the stream segmentation of TCP and congestion window information to continuously adapt the assigned volume to each server in proportion to the bandwidth-delay product to best approximate the optimal data partitioning. Analytical results, simulation and Internet experiments with a transport-layer implementation characterize the performance and the resource requirements of TCP-PARIS and allow a comparison with related protocols. Extensive simulations with varying network and application parameters show download time reductions of up to 52% compared to single-flow downloads and up to 52% compared to related protocols.