Showing papers by "Deutsche Telekom published in 1998"

Spatio-temporal radio channel characteristics in urban macrocells

Abstract: The performance assessment of new mobile radio base station (BS) transceiver concepts with adaptive intelligent antennas requires realistic directional radio channel models. An appropriate model is derived from the results of an extensive uplink sounding campaign performed at 1.9 GHz in a urban macrocell within the city of Frankfurt. In the experiments the wideband sounder RUSK XL was applied for synthetic aperture reception. The directional multipath propagation is characterised by means of delays, directions of arrival (DOA) at the BS antenna array and mean powers of the multipath components. The coupled delay-DOA-power information is determined by an adaptation of the 2-D unitary ESPRIT algorithm. It can be used directly to configure fading simulators for multiple antenna reception which reflect real-world small-area radio channel properties in simulations at the link level. Additionally, probability distribution functions for excess delays, DOAs and mean powers are derived from the measurement results. They are useful for consideration of directional propagation effects in investigations of the cellular system behaviour.

Public key encryption and digital signatures based on permutation polynomials

Abstract: Permutation polynomials over Zn form the basis of the RSA and Dickson public key schemes. Previously, however, only those permutation polynomials whose inverse permutation polynomial was easy to evaluate have been used in cryptography. The authors propose a way to avoid this restriction in public key cryptography by implementing secret key decryption and signature generation by computation of the gcd of two polynomials. This allows the implementation of new classes of public key scheme.

On the degradation of OFDM-signals due to peak-clipping in optimally predistorted power amplifiers

Abstract: The intermodulation noise in OFDM bandpass signals after passing an optimally predistorted power amplifier is investigated by a combination of analytical and numerical calculation. The results are illustrated for several modulation alphabets and it is shown that with ideal predistortion and a small symbol alphabet only a few dB of power back-off are required to achieve small error probabilities.

Byte Code Verification for Java Smart Card Based on Model Checking

Abstract: The paper presents a novel approach to Java byte code verification: The verification process is performed “offline” on a network server, instead of incorporating it in the client. Furthermore, the most critical part of the verification process is based upon a formal model and uses a model checker for checking the verification conditions. The result of the verification process can be securely communicated to the runtime platform with cryptographic means.

Integrated optical circuit

Abstract: The invention relates to an integrated optical circuit comprising a silicon substrate (1) and waveguides (2, 3) arranged thereon. At least one photonic crystal is provided as a waveguide, which is formed by a mesh of needles (6). The needles (6) can be produced by corpuscular radiation deposition.

The specific absorption rate in a spherical head model from a dipole with metallic walls nearby

Abstract: The head of the user of a mobile telephone is modeled by a lossy dielectric sphere excited by the near field of a dipole antenna and the effects of a metallic wall placed close to this system are analyzed. Three wall orientations are used and the changes in specific absorption rate (SAR) with wall or antenna distance from the sphere are investigated. When the wall is closer than 100 mm to the dipole-sphere system, it can have a strong influence on the input impedance of the antenna and can cause significant increases in the SAR in the head. When a constant radiated power of the dipole antenna is assumed, the maximum value of SAR averaged over 10 g of tissue within the sphere is increased by 60% when the wall is as close as 30 mm from the surface of the sphere. For a dipole excited by a constant current source, the increase is less than 10% and occurs when the wall is 120 mm from the surface of the sphere. Although the distances and configurations analyzed may not represent the way the majority of people use mobile telephones, it is important to examine unusual situations to determine the extent of the SAR enhancement problem.

Low overhead pilot-aided 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 (e.g. wireless ATM). For such applications the 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. A synchronization concept is presented which uses only one pilot FFT symbol for all the required synchronization tasks.

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.

Protection against misuse of chip cards involves first user function enabling user to supply optionally selected private personal number when data and/or functions are used for first time

Abstract: The method involves providing access protection to data and/or functions on the chip card with a private personal number. The card has a first user function enabling the user to supply an optionally selected private personal number when the data and/or functions are used for the first time. Entry of this number sets the data and/or functions into a used state.

Method and arrangement for generating binary sequences of random numbers

Abstract: The aim of the invention is to provide an inexpensive method and an arrangement for generating binary sequences of random numbers. The invention should also be easy to integrate onto a chip card. The inventive method is based on the principle of the random path selection of photons in a beam splitter and the generation of a random numbers by means of two detectors (D10; D21) situated downstream of a beam splitter (ST2). According to the invention, a low-power light source (L) is used to produce the photons and an additional beam splitter (ST1) is arranged upstream of the original beam splitter (ST2). The photons emitted by the light source (L) for a set measuring period are split up by the beams splitters (ST1; ST2) arranged one after the other in the beam path of the light source (L). The random sequence is generated when the splitting up of the photons is matched with a predetermined photon model. The invention provides an inexpensive random-check generator which is easy to integrate onto a chip card, especially because of the light source (L) used.

Method for increasing the data transfer rate while ensuring real time mode

Abstract: The inventive method provides a solution ensuring data transfer in real time mode for individual user/client even when a maximum number user/clients are simultaneously accessing the data network. The inventive solution provides that, if necessary, an ISDN data connection, through which data transfer can be carried out in real time mode, is connected in addition to the existing standard data transfer path between the interactive IVS server system of the on-line system and a user/client ISDN data device. The invention can be used especially in the area of on-demand services such as audio on demand, music on demand, books on demand, clips on demand, news on demand, still pictures on demand, video on demand via ISDN, on-demand services via wide band communications networks and on-demand services via special networks.

Polarization-shifting method for step interferometry

Abstract: A phase step interferometry system using polarization shifting is described. The device is essentially a Mach-Zehnder interferometer in which the polarization of light travelling through one arm is orthogonal to the polarization of light travelling through the other arm. At the interferometer output we place a quarter-wave plate with its fast axis at with respect to the polarization directions and a polarizer. By rotating the polarizer, the interfering waves acquire an extra phase (of topological origin) to that expected from the calculations of optical path lengths, and thus, arbitrary phase shifts can be induced. Then, from a set of interferograms recorded while the reference phase is changed, the `dynamical' phase difference (e.g. the phase profile of an object placed in one of the interferometer arms) can be reconstructed by using techniques of phase-shifting interferometry.

Method of transferring information matched to performance of terminal over communications network involves identifying terminal prior to setting up connection

Abstract: The method involves transferring the identifier of a specified terminal (10-30) to the information source (40) to which it is to be connected or to a connected central device (50), in which characteristics of each connected terminal are stored, before setting up a connection between the terminal and information source. The information to be transferred is adapted to the performance of the identified terminal and transferred via the communications network (45) to the terminal.

On the performance of the DVB-T system in mobile environments

Abstract: Mobile multimedia services may become an important feature of terrestrial networks for many applications. One possible scenario to offer digital TV services for mobile and portable receivers is to use the DVB-T specifications that may allow high data rate transmission in an 8 MHz UHF channel. Although this specification was designed for fixed reception, some of its robust modes might allow mobile reception of TV-services. By means of theoretical investigations, simulations, laboratory tests and field trials, we analyse the behaviour and limits of the DVB-T standard in mobile environments. It seems that the Doppler shift is not necessarily the limitation. Rather, it is the lack of time interleaving that might pose problems.

Adaptive receiver for CDMA base stations

Abstract: An adaptive receiver for base stations of CDMA mobile wireless systems corresponding to the IS-95 Standard. The receiver is designed as an incoherent rake receiver and includes an antenna array. The receiver is capable of analyzing a plurality of components of the same signal transmitted by a mobile station arriving at the antenna array via different propagation paths and from different directions with a time offset. To form virtual antenna directivity patterns for individual rake processing paths, which are adjusted to the directions of incidence of the signal paths to be analyzed, direction signature vectors are calculated and made available to the processing paths together with a signal propagation time that is required for synchronizing the signal components. The direction signature vectors are calculated iteratively from the antenna correlation matrices formed recursively for all possible signal delay times from pulse responses of the antenna arrays. The signal components associated with the processing paths are selected according to the average path powers determined for the individual signal delay times, and the path powers are also calculated from the antenna correlation matrices.

Device for implementing a block-ciphering process

Abstract: The invention relates to a device for implementing a block-ciphering process using an encryption/decryption arithmetic-logic module (3) which is supplied with the data stream of word length j≦n to be ciphered. The invention is characterized in that the arithmetic-logic module (3) includes a plurality of encryption/decryption elements (5), each of which forms a stage of a computing pipeline, the stages being designed such that they operate independently of each other in different modes of operation and with different keys. Supported by further components and data paths surrounding the encryption/decryption arithmetic-logic module (3), the invention allows up to p data streams, each with independently selectable word lengths j≦n and modes of operation, to be encrypted or decrypted simultaneously. In addition, the architecture of the device permits different logical data streams to be processed directly consecutively and free of conflict on the physical channels provided by the hardware resources.

Method and device for extracting signals out of a glass fiber

Abstract: In a method and a device for extracting signals out of a glass fiber without any detectable interference occurring, in particular without the signals propagating through the glass fiber experiencing any transmission loss, light that emerges laterally from the glass fiber due to scattering (Rayleigh scattering) processes, which are in existence anyway, is directed at a photodetector. In the process, the emerging light can be directed by focussing elements at the photodetector or at the input face of another glass fiber. In addition, the emerging light can be directed both directly as well as via at least one reflector at the photodetector.

Transcoder for decoding encoded TV programs

Abstract: The invention pertains to a transcoder provided with a control unit and intended for decoding encoded TV programs Said transcoder has an input for entering an encoded TV program, a decoding device for decoding an encoded TV program into a format which can be played on a television set, an output which can be connected to said television set and is designed to enter the encoded TV program into the television set for play, an interface for an identification or key component, to be used for validation of the decoding device, as well as an interface for a control unit in the transcoder The transcoder according to the invention is characterized in that the interface for the identification or key component is located in said control unit

Management of all-optical WDM networks: First results of European research project MOON

Abstract: This paper presents first results of the European research project MOON. It is organized as follows. As a starting point, basic concepts of all-optical networks which are relevant for management are described. The results are compared with the Synchronous Digital Hierarchy (SDH) which is the state-of-the-art transport technique. Then, the general architecture for a TMN conforming management of all-optical networks is illustrated. As a main point of the paper, the impact of transparency limitations on transmission, OAM (operation, administration, maintenance), and management is discussed. A functional architecture will be presented which describes the network in a formalized way. Based on this description, different approaches for the transmission of OAM overhead are addressed. The information model of MOON is described and compared to the SDH model. Finally, concepts for the implementation of the management system are presented.

System for transmitting high-speed added-value services in terrestrial digital broadcasting

Abstract: The invention relates to a broad-band multi-frequency block X-DAB transceiver system for interference-free transmission of high data speed value-added services to mobile receivers in an analog TV channel. The system provides considerable flexibility with regard to error control profiles and therefore data rates, and enables unbalanced error control profiles and hierarchic transmission to be carried out. The invention discloses a method for transmitting high-speed added-value services to mobile subscribers according to the X-DAB system (Extended Digital Broadcasting System) based on several, mainly four, simultaneously broadcast adjacent X-DAB frequency blocks in a common wave network in which relevant service content corresponding to source coded digital input data flow is multiplexed.

OFDM and related methods for broadband mobile radio channels

Abstract: A comparison is made of multicarrier and single carrier modulation schemes for radio communication systems. In both schemes, the fast Fourier transform (FFT) and its inverse are utilized. For OFDM (orthogonal frequency division multiplexing), the inverse FFT transforms the complex amplitudes of the individual subcarriers at the transmitter into the time domain. At the receiver, the inverse operation is carried out. For single carrier modulation, the FFT and its inverse are used at the input and output of the frequency domain equalizer in the receiver. Different single carrier and multicarrier transmission systems are simulated with time-variant transfer functions measured with a wideband channel sounder. For OFDM, the individual subcarriers are modulated with fixed and adaptive signal alphabets. In particular, the performance degradation of single carrier and multicarrier transmission due to pilot-aided channel estimation is analyzed.

Stationary operation arrangement for mobile communication instrument

Abstract: The arrangement includes a hardware interface for the connection to the mobile communication instrument (1), at least one network connection (101) for a private exchange system (7), and a converter circuit (6) for converting different hardware and software protocols of mobile communication instruments and fixed network. The arrangement includes at least one fixture for accommodating a mobile communication instrument, a network instrument for the DC supply and/or charging of a rechargeable battery in the mobile communication instrument, and a connection to an external antenna. At least one hardware interface is provided for the connection to an interface of the mobile communication instrument (1) for external instruments. At least one network connection (101) is provided for a connection with a private exchange system (7). A converter circuit (6) is provided for converting different hardware and software protocols of mobile communication instruments and fixed network.

The Application of Intelligent and Mobile Agents to Networks and Service Management

Abstract: Agent technology promises to increase the flexibility and power of telecommunications management systems and services. This paper describes ongoing work that, through prototyping and experimentation, is aiming to understand the practical implications and benefits of applying agent technology to network and service management.

Method for dialog control of voice-operated information and call information services incorporating computer-supported telephony

Abstract: A method provides customer with simple and flexible dialog control and faster access to the desired information. In response to a customer call, a control program for dialog control created with the aid of a graphical editor as a flow chart is started, once access authorization is checked. All of the computer-supported telephony (CTI) information input modules and information output modules provided within the framework of the dialog control service in question, which are subject to continuous monitoring, are simultaneously made available in parallel to the customer via a control module for controlling the resources. The customer can actively intervene in the dialog already during the welcome via the information input modules allocated to him. The dialog commences again at the place designated by the customer. The method is suitable for at least information, news and connection services which are based on very significant parallelism and which are configured for mass telephony.

The application of code division multiple access for transport overhead information in transparent optical networks

Abstract: Summary form only given. The operation, administration, and maintenance (OAM) of a transport network require the generation, transmission, and detection of OAM signals that are related to each network layer. In the modelled system Gold codes have been applied for transport of the OAM-signals at channels, which have been modulated externally (by Mach-Zehnder modulators) at different modulation levels in order to characterize the influence of the modulation depth. The simulation has shown the feasibility of CDMA for transport of OAM-signals with a bandwidth up to l0-kbit/s per optical carrier in transparent optical networks with minimised distortion of the high speed data stream.

Public mobile communication system compatible wireless communication system

Abstract: The invention relates to a wireless communication system which, at a radio interface, is substantially compatible with a public mobile communication system provided with at least one authentication function whereby the base station of the wireless communication system is fitted with devices for reading and writing information from/on identification modules and is equipped with suitable software so that home location register (HLR) functions or authentication centres(AUC) can be provided along with the data filed on the identification module. Complete non-manipulative initialization parameters of the wireless base stations that the network operator wishes to keep under control are also filed onto the identification system module.

Visualising the Behaviour of Intelligent Networks

Abstract: Telecommunication systems in general, and Intelligent Networks as well, are large distributed systems with a high degree of concurrency. To investigate the specific aspects of the behaviour of such systems adequate formal specification techniques are required. In this paper, we show how designers of services in an Intelligent Network can use Coloured Petri Nets, to obtain a description of the services which on the one hand is precise and unambiguous, and on the other hand provides the basis for a comprehensive and thorough understanding of the behaviour by visualising the processes. Coloured Petri Nets supported by adequate tools can therefore serve as basis for investigations of new services to be provide.