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.

Method for co-channel interference cancelation in a multicarrier communication system

Abstract: The present invention relates to an interferance signal cancel ing method, a receiver using the same and a digital multi-carrier communication system comprising such a receiver. A main aspect of the present invention is to apply an interference cancellation scheme to a digital multi-carrier communication system. By using a digital multi-carrier communication system, the effect of the inter-symbol interference is avoided. As a result the receiver (8) comprises a plurality (L) of interference cancellers (171-17L) each of which is assocaiated to a respective one of sub-carrier signals for canceling only co-channel interference.

Iterative mesh deformation for dense surface tracking

Abstract: In this paper we present a new method to capture the temporal evolution of a surface from multiple videos. By contrast to most current methods, we introduce an algorithm that uses no prior of the nature of tracked surface. In addition, it does not require sparse features to constrain the deformation but only relies on strictly geometric information : a target set of 3D points and normals. Our approach is inspired by the Iterative Closest Point algorithm but handles large deformations of non-rigid surfaces. To this end, a mesh is iteratively deformed while enforcing local rigidity with respect to the reference model. This rigidity is preserved by diffusing it on local patches randomly seeded on the surface. The iterative nature of the algorithm combined with the softly enforced local rigidity allows to progressively evolve the mesh to fit the target data. The proposed method is validated and evaluated on several standard and challenging surface data sets acquired using real videos.

Investigation of brain potentials in sleeping humans exposed to the electromagnetic field of mobile phones.

Abstract: An investigation was made of 8-hour EEG tracings of sleeping humans exposed to the electromagnetic field of a GSM-standard mobile phone. To analyze the EEG-patterns, manual scoring, nonlinear dynamics, and spectral analysis were employed. It was found that, when human beings were exposed to the electromagnetic field of a cellular phone, their cerebral cortex biopotentials revealed an increase in the α-range power density as compared to the placebo experiment. It was also found that the dimension of EEG correlation dynamics and the relation of sleep stages changed under the influence of the electromagnetic field of a mobile phone.

Audio and video channel impact on perceived audio-visual quality in different interactive contexts

Abstract: With the advent of audio-visual IP clients, video telephony becomes a realistic option in many application scenarios. In order to guarantee an adequate quality to its users, providers of audio-visual telephony services need to know the impact of the audio and video transmission channel characteristics on perceived Quality of Experience (QoE) in a realistic interactive setting. For this aim, a conversational video telephony experiment was conducted where the audio and video channel settings were adjusted in a controlled way, and participants were asked about the perceived audio, video and overall quality after carrying out a conversation over the audio-visual channel. We analyze the results with respect to the impact the two modalities have, as well as with respect to the impact of the conversation scenario.

On the achievable information rate with peak-power-limited orthogonal frequency-division multiplexing

Abstract: This paper addresses the problem of determining the statistical distribution of the peak-to-average power ratio (PAR) of orthogonal frequency-division multiplexing (OFDM) transmit signals. In practice, transmission systems are amplitude-limited, thus the large peak values of OFDM signals are clipped and nonlinear distortion follows. In order to avoid the resulting degradations, i.e., spectral widening and increased bit-error rate, a systematic construction of OFDM signals without large peaks is desired. The paper provides new results on the PAR distribution and hence on the achievable information rate with OFDM signals that are peak-limited. In particular, it is shown that in the case of phase-shift-keying (PSK) subcarrier modulation, the frequently applied model of Gaussian data coefficients is not appropriate. By solving an integral equation, new analytic expressions for the PAR and the achievable information rate are derived. Comparison with simulation results confirms that the new model is accurate for all ranges of practical interest.