Jens Jelitto

A multiple input-multiple output channel model for simulation of Tx- and Rx-diversity wireless systems

Space-time receivers for wireless communication systems offer the possibility to have both Tx- and Rx-antennas. For a realistic simulation of such systems, a multiple input multiple output (MIMO) spatial channel model is required which reasonably characterizes the space- and time-variant effects of the mobile radio channel. This paper describes a space-time vector channel model with realistic fading simulation for different scenarios. Mutual correlation between the fading coefficients is considered. This allows an estimation of the diversity gain, that can be achieved with space-time receivers in different scenarios.

Learning pronunciation dictionary from speech data

An algorithm and first results from investigations in automatically learning pronunciation variations from speech data are presented. Pronunciation dictionaries establish an important feature in state-of-the-art speech recognition systems. In most systems only simple dictionaries containing the canonical pronunciation forms are implemented. However, for a good recognition performance more sophisticated dictionaries including pronunciation variations are essential. The generation of such dictionaries by hand is an extremely time consuming task, and the introduction of errors and inconsistencies is probable. The authors show an approach for automatically generating suitable pronunciation dictionaries from the speech database itself, as they are desirable not only for speech recognition tasks but also for speech technology and phonologic research in general. The only knowledge sources besides the database are the (unlabeled) signals and their transliterations on word level. First experiments yielding promising results have been performed with the software system DataLab, which integrates the recognition system of the TU Dresden.

From Smart Antennas to Reduced Dimension Space-Time Processing

The Integrated Broadband Mobile System (IBMS) is a concept for future wireless communications systems that has been developed in order to integrate heterogeneous services and applications into a common framework. Smart antennas are used as the enabling technology to support high and variable data rates. A hardware testbed was developed for the investigation of algorithms and real-time aspects of smart antennas, which uses separate stages for processing of spatial and temporal information. Research results indicate that the system performance can be enhanced using a space-time processor (STP) which carries out spatial and temporal information processing jointly. This paper reviews the IBMS physical layer and presents the results obtained with the smart antenna demonstrator. A new STP concept with reduced signal dimension by means of the KarhunenLoeve-Transformation (KLT) is introduced and analyzed. Übersicht Das Integrierte Breitbandbandige Mobilkommunikations-System (IBMS) ist ein Konzept für die zukünftige Mobilkommunikation, welches durch Einsatz verschiedener Schlüsseltechnologien die Integration verschiedenartiger Dienste in ein gemeinsames Gesamtsystem ermöglicht. Zur Bereitstellung hoher und variabler Datenraten werden in diesem System intelligente Antennen eingesetzt. Algorithmen zur adaptiven Strahlformung wurden im Hinblick auf ihre Leistungsfähigkeit unter Echtzeitbedingungen untersucht und auf einem Hardware-Testbed demonstriert, das räumliche und zeitliche Informationen getrennt verarbeitet. Darüber hinaus wurden kombinierte Raum-Zeit-Verarbeitungsansätze analysiert, welche der getrennten räumlichen und zeitlichen Verarbeitung in vielen Bereichen überlegen sind. In dieser Arbeit werden die wichtigsten Parameter der physikalischen Schicht des IBMS zusammengefaßt und der .IBMS Smart Antenna Demonstrator* vorgestellt. Darüber hinaus wird ein neuartiges Konzept zur dimensionsreduzierten Raum-Zeit-Verarbeitung vorgestellt und analysiert, welches auf der Karhunen-Loeve-Transformation (KLT) beruht. Für die Dokumentation Strahlformung / Raum-Zeit-Signalverarbeitung / Low-rank modeling / Karhunen-Loeve-Transformation / IBMS Frequenz 55(2001) 5-6

Integrated broadband mobile system (IBMS) featuring smart antennas

IBMS is a concept for future mobile communication systems to provide a large range of data rates with different degrees of mobility. The integration of heterogeneous services and communication systems requires a common Network Access and Connectivity CHannel (NACCH) for basic signaling to provide permanent network access. Smart Antennas are utilized to adaptively enable a trade-off between mobility and data rate.

Reduced Complexity Space-time Optimum Processing

New emerging space-time processing technologies promise a significant performance increase of wireless communication systems. The particular application and scenario strongly influences the amount of possible performance and capacity increase if antenna arrays are deployed at the basestation (BS) and/or at the mobile terminal (MT). The achievable gain is mainly determined by the spatial correlation properties of the underlying physical transmission channel.

A stochastic vector channel model-implementation and verification

The simulation of space-time receivers for wireless communication systems requires a spatial channel model which reasonably characterizes the time-variant effects of the mobile radio channel. This paper describes a space-time vector channel model with stochastic fading simulation and its effective implementation for bit-level simulations. Measurements have been analyzed in order to verify the assumptions of the channel model.