Showing papers by "Johannes B. Huber published in 2004"

Precoding in multiantenna and multiuser communications

Abstract: In this paper, Tomlinson-Harashima Precoding for multiple-input/multiple-output systems including multiple-antenna and multiuser systems is studied. It is shown that nonlinear preequalization offers significant advantages over linear preequalization which increases average transmit power. Moreover, it outperforms decision-feedback equalization at the receiver side which is applicable if joint processing at the receiver side is possible, and which suffers from error propagation. A number of aspects of practical importance are studied. Loading, i.e., the optimum distribution of transmit power and rate is discussed in detail. It is shown that the capacity of the underlying MIMO channel can be utilized asymptotically by means of nonlinear precoding.

Lattice-reduction-aided broadcast precoding

Abstract: A precoding scheme for multiuser broadcast communications is described, which fills the gap between the low-complexity Tomlinson-Harashima precoding and the sphere decoder-based system of Peel et al. Simulation results show that, replacing the closest-point search with the Babai approximation, the full diversity order supported by the channel is available to each user, as in the system of Peel et al., and unlike Tomlinson-Harashima precoding, which suffers some diversity penalty. The complexity of the scheme is similar to that of Tomlinson-Harashima precoding.

Precoding for point-to-multipoint transmission over MIMO ISI channels

Abstract: Tomlinson-Harashima type precoding for point-to-multipoint transmission over linear dispersive channels which suffer from intersymbol interference and multiuser interference is reviewed. The tasks of the matrix filters at the joint transmitter, their calculation by spectral factorization, and the necessity of an optimized processing order are discussed. The performance of precoding is covered by numerical simulations.

Hidden Markov Modeling of Error Patterns and Soft Outputs for Simulation of Wideband CDMA Transmission Systems

Abstract: Summary In this paper, a Hidden Markov Modeling (HMM) technique for a fast and accurate simulation of bit errors and soft outputs in wireless communication systems is presented. HMMs with continuous probability distributions are considered. Soft outputs and bit errors are combined to error patterns . We focus on binary phase–shift keying (BPSK) modulation for direct–sequence spread spectrum (code–division multiple access, CDMA) transmission as proposed e.g. ∼for the third generation wireless communication system UMTS (uplink for the frequency division duplex mode (FDD)). Comparisons of simulated bit error rates for HMM models and Rake receivers are shown for AWGN, flat fading, and vehicular channel conditions. In order to assess the ability of the HMM to describe the dynamical behaviour of the channel a comparison for transmission with interleaving and convolutional coding is presented. Furthermore calculated autocorrelation functions of the error patterns and error gap distributions corresponding to the Rake receiver and to the HMM, respectively, are presented. Our investigations show a strong dependence of the required HMM order on E b / N 0 and the channel conditions. The degree of accordance of the HMM outputs and the training data is examined based on calculated statistical scoring indicators.

Analytical derivation of EXIT charts for simple block codes and for LDPC codes using information combining

Abstract: The extrinsic information transfer (EXIT) chart describes the input-output behavior of a decoder by means of the mapping from a-priori information and channel information to extrinsic information. In this paper, we consider single parity check and repetition codes over binary-input symmetric memoryles channels. Using the concept of information combining, we derive bounds on the extrinsic information for these codes, which depend only on the a-priori information and on the channel information, but not on the channel models. The bounds are applied to the EXIT charts of these codes and to the EXIT charts of low-density parity-check codes.

Bounds on information combining for parity-check equations

Abstract: When several independent channels are coupled by a parity check constraint on their inputs, the mutual information between the input of one channel and the outputs of all other channels can be expressed as a combination of the mutual information between the input and the output of each individual channel. This concept is denoted as information combining. For binary-input symmetric discrete memoryless channels, we present bounds on the combined information which are only based on the mutual information of the channels. Furthermore, we show that these bounds cannot be further improved. Exact expressions are provided for the case that all channels are binary symmetric channels and for the case that all channels are binary erasure channels.

Method And Apparatus For The Digitization Of And For The Data Compression Of Analog Signals

Abstract: The invention is based on the idea of providing a method for high-resolution, waveform-preserving digitization of analog signals, wherein conventional scalar logarithmic quantization is transferred to multi-dimensional spherical coordinates, and the advantages resulting from this, e.g., a constant signal/noise ratio over an extremely high dynamic range with very low loss with respect to the rate-distortion theory. In order to make use of the statistical dependencies present in the source signal for an additional gain in the signal/noise ratio, the differential pulse code modulation (DPCM) is combined with spherical logarithmic quantization. The resulting method achieves an effective data reduction with a high long-term and short-term signal/noise ratio with an extremely small signal delay.

Verfahren und vorrichtung zur digitalisierung sowie zur datenkomprimierung analoger signale

Abstract: Die Erfindung beruht auf dem Gedanken, ein Verfahren zur hochauflosenden, wellenformerhaltenden Digitalisierung analoger Signale vorzusehen, wobei die ubliche skalare logarithmische Quantisierung auf mehrdimensionale Kugelkoordinaten ubertragen wird und sich somit die hieraus resultierenden Vorteile wie z. B. ein konstanter Storabstand uber einen extrem hohen Dynamikbereich bei einem sehr geringen Verlust in Bezug auf die Rate-Distortion-Theorie ergeben. Um die im Quellensignal vorhandenen statischen Abhangigkeiten fur einen weiteren Storabstandsgewinn ausnutzen zu konnen, wird die Differentielle Pulscodemodulation (DPCM) mit spharisch logarithmischer Quantisierung kombiniert. Das resultierende Verfahren erzielt eine wirksame Datenreduktion mit einem hohen Langzeit- sowie Kurzzeitstorabstand bei extrem geringer Signalverzogerung.

Information processing characteristic for bit interleaved coded space-time modulation

Abstract: Bit interleaved coded space-time modulation with iterative decoding (BICSTM-ID) [1], [2] is an attractive strategy to achieve high power efficiency close to capacity limit by applying turbo principle to multiple-input and multiple-output (MIMO) channels. In this paper, Information Processing Characteristic (IPC) analysis [3] is extended to MIMO systems in order to fully characterize the BICSTM-ID scheme based on a new equivalent model of combined binary input channels. The analysis results show that the IPC analysis offers an unified aspect for BICSTM and BICSTM-ID from an information theoretical point of view and provides a valuable design guideline for BICSTM-ID as well. Moreover, IPC based upper and lower bounds on BER performance [4] are applied to BICSTM-ID, which are confirmed by simulations and seem to be very useful for performance estimation of coding schemes for space-time coded MIMO channels.

Spherical Logarithmic Quantization and its Application for DPCM Dedicated to Prof. Dr. Karlheinz Tron the occasion of his retirement and 65th birthday

Abstract: A new method for efcient digitizing analog signals while preserving the original waveform as close as possible with respect to the relative quantization error is presented. Logarithmic quantization is applied to short vectors of samples represented in sphere coordinates. The resulting advantages, i.e. a constant Signal-to-Noise Ratio over a very high dynamic range at a small loss with respect to rate-distortion theory are discussed. In order to increase the Signal-to-Noise Ratio (SNR) by exploitation of correlations within the source signal, a method of combining differential pulse- codemodulation (DPCM) with spherical logarithmic quantization is presented. The resulting technique achieves an efcient digital representation of waveforms with a high longterm as well as segmental SNR at an extrem low delay of the signal.

Method and device for digitization and data compression of analog signals

Abstract: The invention relates to a method for high-resolution, wave-form maintaining digitization of analog signals. The usual scalar logarithmic quantization is transferred to multidimensional spherical coordinates whereby the resulting advantages such as a constant signal-to-noise ratio arise over an extremely high dynamic range with very little loss in relation to the distortion-theory rate. In order to use the statistic dependencies available in the source signal for another gain in the signal-to-noise ratio, the differential pulse code modulation (DPCM) is combined with spherically logarithmic quantization. The resulting method makes it possible to reduce data in an effective manner with a high long-term distance for an extremely small signal delay.