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.

Cross-layer multi-hop wireless routing for inter-vehicle communication

Abstract: Ad-hoc networking provides a cost-effective support structure for inter-vehicle communication. A decentralized peer-to-peer information dissemination architecture is well suited for automotive applications that need to exchange data having local relevance. Routing, however, is challenge in a vehicular scenario because of the associated dynamism in network topology and variations in driving conditions. In this work we present a cross-layer ad-hoc routing approach based on link connectivity assessment in the network topology. We suggest a framework for proactive enhancements to the optimized link state routing (OLSR) protocol and implement the proposed measures within the protocol format. We further deploy an IEEE 802.11b based vehicular network and demonstrate the effectiveness of link-quality assessment based enhancements in improving the performance of inter-vehicle ad-hoc routing. Through actual test-runs, we show that the enhanced protocol is more responsive to variations in network connectivity and can take preemptive actions in choosing stable and durable routes. The routing methodology suggested in this work leverages cross-layer interactions among the networking, data-link, and physical layers, for enhanced adaptability to varying network topology and link states. The main contributions of this work are as follows: introduction of link-quality assessment methodology for enhanced adaptability of ad-hoc routing in a dynamically changing topology, delineation of the framework of a proactive topology-adaptive ad-hoc routing protocol in a vehicular scenario, and demonstration of effectiveness of the proposed routing enhancements in an IEEE 802.11b based vehicular test-bed.

Synchronization for single carrier modulation with frequency domain equalization

Abstract: This paper deals with the synchronization of single carrier transmission with frequency domain equalization (FDE) for broadband mobile radio applications. For such applications carrier frequency and temporal position of the FFT (fast Fourier transform) window have to be synchronized. Furthermore, an estimation of the channel transfer function is necessary.

Chipkarte, insbesondere Guthabenkarte

Abstract: Die Erfindung betrifft eine Chipkarte, insbesondere Guthabenkarte, mit mindestens einem elektronischen Datentrager, in die eine optische Anzeige integriert ist, die ein Flachenleuchtkorper aus polymeren Material, insbesondere ein Anzeigeelement aus pLEDs ist. Mit der Erfindung ist es moglich, den Informationsstand des Datentragers unmittelbar, d. h. ohne externes Lesegerat auf der optischen Anzeige sichtbar zu machen. Hierzu wird beispielsweise fur eine benutzerdefinierte Zeitspanne ein Stromkreis durch einen Mikroschalter geschlossen. Uber einen Taster kann bei der Abfrage die Informationsabfolge gesteuert werden. Die Energieversorgung erfolgt durch ein Solarzellenmodul oder eine Primarbatterie. Daruber hinaus kann beispielsweise ein Kondensator als vorsorglicher Energiespeicher dienen.

Theoretical and experimental analysis of the channel busy fraction in IEEE 802.11

Abstract: Optimizing the operation of IEEE 802.11 networks requires to estimate the load of the wireless channel. The channel busy fraction, which is the fraction of time in which the wireless channel is sensed busy due to successful or unsuccessful transmissions, can be used as such indicator. It can be obtained from e.g. the IEEE 802.11k channel load report or hardware-specific interfaces. Previously, the channel busy fraction has been used as a metric for different purposes such as routing and admission control. However, a thorough evaluation of the relationship between the busy fraction and other important characteristics such as the collision probability and throughput is missing. In this paper, we present an analytical model to study the channel busy fraction in non-saturated IEEE 802.11 networks. We validate the model with measurements in a testbed. The predictions from the model match measurements well. Furthermore, we demonstrate how to apply the model to estimate the available link bandwidth. Using measurements obtained from a testbed operated at 6 Mbit/s, we show that the channel busy fraction allows an accurate prediction of the available bandwidth with an error smaller than 70 Kbit/s.

Picture-transmitting remote object inspection system

Abstract: A remote object inspection system has a picture-taking system arranged at the site of the object (43) to be examined, an observation station located at a distance therefrom for evaluating the pictures and remote controlling the picture-taking system, and an intermediate, narrow band telecommunication path of transmission (7). According to the invention, a unit (42) for determining the state of the system constantly detects the total, picture transmission-relevant state of the system and automatically controls the picture data compression and/or reduction and/or the number of telecommunication channels used in a transmission bundle depending on the detected data, in order to achieve the desirable picture quality in the momentary situation and the best possible on-line picture appearance. The invention has applications for example in telemicroscopy, tele-endoscopy and telesonography.