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 reducing the out-of-band emission in AM transmitters for digital transmission

Abstract: The problem associated with digital transmission using existing AM transmitters is that the out-of-band emission that occurs must be reduced in order to comply with the ITU mask, as the shoulder distances that can be achieved by the AM transmitters are not sufficient for a satisfactory compensation. The signals that are required to control the AM transmitters, (amplitude signal and phase-modulated RF signal), are formed from the digital modulation signal by a Cartesian → polar transformation, whereby the bandwidth for the amplitude signal and RF signal reaches a value, which causes an unacceptable out-of-band emission. To prevent this, the invention provides methods for digital modulation, which avoid the zero point by a wide margin in their vector diagram representations, i.e. which form a 'hole' around the 0/0 point. Modulation methods of this type are referred to as offset modulations and coded modulations. A variant of 16APSK is particularly suitable, as a higher net data throughput can be achieved with only 16 set points and negligible error protection coding is required. To transmit an OFDM signal, the 'hole' in the vector diagram is obtained by offsetting the zero crossings for the I(t) and Q(t) signals and the latter is achieved by the insertion of a pulse into the subsequent component, e.g. I(t), if the other component Q(t) already falls short of a defined threshold value. A BPSK test sequence for measuring the radio channel can be used by means a modification, in which a modulation signal is formed by inserting a pulse between two pulses with a change of sign bit, said modulation signal having a 'hole' around the 0/0 point. The size of the hole can be adjusted by the inserted pulse.

Quality-aware segment transmission scheduling in peer-to-peer streaming systems

Abstract: In peer-to-peer (P2P) mesh-based streaming systems, each video sequence is typically divided into segments, which are then streamed from multiple senders to a receiver. The receiver needs to coordinate the senders by specifying a transmission schedule for each of them. We consider the scheduling problem in both live and on-demand P2P streaming systems. We formulate the problem of scheduling segment transmission in order to maximize the perceived video quality of the receiver. We prove that this problem is NP-Complete. We present an integer linear programming (ILP) formulation for this problem, and we optimally solve it using an ILP solver. This optimal solution, however, is computationally expensive and is not suitable for real-time streaming systems. Thus, we propose a polynomial-time approximation algorithm, which yields transmission schedules with analytical guarantees on the worst-case performance. More precisely, we show that the approximation factor is at most 3, compared to the absolutely optimal solution as a benchmark. We implement the proposed approximation and optimal algorithms in a packet-level simulator for P2P streaming systems. We also implement two other scheduling algorithms proposed in the literature and used in popular P2P streaming systems. By simulating large P2P systems and streaming nine real video sequences with diverse visual and motion characteristics, we demonstrate that our proposed approximation algorithm: (i) produces near-optimal perceived video quality, (ii) can run in real time, and (iii) outperforms other algorithms in terms of perceived video quality, smoothness of the rendered videos, and balancing the load across sending peers. For example, our simulation results indicate that the proposed algorithm outperforms heuristic algorithms used in current systems by up to 8 dB in perceived video quality and up to 20% in continuity index.

Quantum cryptography system for a secure transmission of random keys using a polarization setting method

Abstract: A quantum cryptography system using electrooptical liquid crystal modulators which change the polarization and which are designed as electrically rotatable retardation plates whose two birefringent axes are rotated by the applied electrical field around an angle θ which depends on the strength of this field A λ/2 retardation plate rotates the elliptically polarized light striking the plate around an angle 2θ at speeds in the microsecond range The quantum cryptography system can be used for interception-proof data transmission over transmission links that are accessible to the public

Traffic control, information and positioning system

Abstract: The system has terminal equipment in vehicles (A,...) for acquiring dynamic traffic information and/or events and passing the information to other traffic in combination with position and time information. The traffic related data (VD) are acquired by vehicles in traffic and passed via an information channel (IK) to passing or overtaking vehicles (C).

Tactile and visual alerts for deaf people by mobile phones

Abstract: In this demo, we present an application for mobile phones which can analyse audio context and issue tactile or visual alerts if an audio event happens. This application can be useful especially for deaf or hard of hearing people to be alerted of audio events happening around them. The audio context analysis algorithm captures data using mobile phone's microphone and checks for changes in audio activities around the user. If such a change happens and also some other circumstances are met, the application issues visual or vibro-tactile alerts (by vibrating mobile phone) proportional to the change in audio context. This informs the user about an event. The functionality of this algorithm can be further enhanced by analysis of user movements.