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 & Terminal (electronics). The organization has 3473 authors who have published 5208 publications receiving 65429 citations. The organization is also known as: DTAG & German Telecom.

Slow and Fast-Light in optical fibers ’ An overview

Abstract: Slow- and fast-light is the control of the velocity of light in a medium by light. As a fascinating new field in physics there is a fundamental interest on this effect on the one side, but on the other side there exist a lot of practical applications for telecommunication and information systems. Among these are optical signal processing, the radio frequency-photonics, nonlinear optics and spectroscopy in time domain. Furthermore, the slow- and fast-light effect can be seen as a key technology for optical delay lines, buffers, equalizers and synchronizers in packed switched networks. To realize the effect there are different methods and material systems possible. Beside these especially the nonlinear effect of stimulated Brillouin scattering (SBS) is of special interest because it has several advantages. This article gives an overview about the fundamentals and limits of the slow-and fast-light effect in general and based on the SBS in optical fibers. Some experimental results which were achieved so far are shown.

37.5-km urban field trial of OFDMA-PON using colorless ONUs with dynamic bandwidth allocation and TCM

Abstract: An OFDMA-PON field trial using coherent detection in upstream and direct detection in downstream on 37.5 km feeder fiber is demonstrated. A power budget supporting 32 cost-effective colorless ONUs with dynamic bandwidth allocation is reported.

Fixed and Mobile Convergence: Needs and Solutions

Abstract: The drivers of Fixed and Mobile Convergence (FMC) are discussed. A reference framework for FMC proposed by European project COMBO is then presented. Some use cases of FMC are described, showing the needs for mutualization and convergence of fixed and mobile broadband networks. Five network scenarios providing technical solutions to FMC use cases are proposed. They target an optimal and seamless quality of experience for the end user together with an optimized network infrastructure ensuring increased performance, flexibility, reduced cost and reduced energy consumption.

Turning adversaries into friends: simplified, made constructive, and extended

Abstract: A liveness contract is an agreement between the specifier of a system and a task to solve, and the programmer who makes her living by delivering protocols. In a shared-memory system, a liveness contract specifies infinite suffixes of executions in which the programmer is required to solve a distributed task. If the behavior of the system does not comply with the specification, no output is required. A convenient way to describe a large class of liveness contracts was recently proposed by Delporte et al. For a system Π of n processes, an adversary is a set A of subsets of Π. The system is required to make progress only in executions in which the set of correct processes is in A. Given an adversary A and a task T, should the programmer sign the contract? Can she deliver? In this paper, we give a very simple resolution of this question for colorless tasks that contrasts with more involved arguments of the original paper of Delpote et al. More importantly, our resolution is constructive -- it tells the programmer how to use A to solve T, when it is solvable. Our framework naturally generalizes to systems enriched with more powerful objects than read-write registers. We determine necessary and sufficient conditions for an adversary A to solve consensus using j-process consensus objects and read-write registers, which resolves an open question raised recently by Taubenfeld.

Centralized coordinated scheduling in LTE-Advanced networks

Abstract: This work addresses the problem associated with coordinating scheduling decisions among multiple base stations in an LTE-Advanced downlink network in order to manage inter-cell interference with a centralized controller. To solve the coordinated scheduling problem, an integer non-linear program is formulated that, unlike most existing approaches, does not rely on exact channel state information but only makes use of the specific measurement reports defined in the 3GPP standard. An equivalent integer linear reformulation of the coordinated scheduling problem is proposed, which can be efficiently solved by commercial solvers. Extensive simulations of medium to large-size networks are carried out to analyze the performance of the proposed coordinated scheduling approaches, confirming available analytical results reporting fundamental limitations in the cooperation due to out-of-cluster interference. Nevertheless, the schemes proposed in this paper show important gains in average user throughput of the cell-edge users, especially in the case of heterogeneous networks.