Bell Labs

About: Bell Labs is a based out in . It is known for research contribution in the topics: Laser & Optical fiber. The organization has 36499 authors who have published 59862 publications receiving 3190823 citations. The organization is also known as: Bell Laboratories & AT&T Bell Laboratories.

Unitary space-time modulation for multiple-antenna communications in Rayleigh flat fading

Abstract: Motivated by information-theoretic considerations, we propose a signaling scheme, unitary space-time modulation, for multiple-antenna communication links. This modulation is ideally suited for Rayleigh fast-fading environments, since it does not require the receiver to know or learn the propagation coefficients. Unitary space-time modulation uses constellations of T/spl times/M space-time signals (/spl Phi//sub i/, l=1, ..., L), where T represents the coherence interval during which the fading is approximately constant, and M

Continuous probabilistic transform for voice conversion

Abstract: Voice conversion, as considered in this paper, is defined as modifying the speech signal of one speaker (source speaker) so that it sounds as if it had been pronounced by a different speaker (target speaker). Our contribution includes the design of a new methodology for representing the relationship between two sets of spectral envelopes. The proposed method is based on the use of a Gaussian mixture model of the source speaker spectral envelopes. The conversion itself is represented by a continuous parametric function which takes into account the probabilistic classification provided by the mixture model. The parameters of the conversion function are estimated by least squares optimization on the training data. This conversion method is implemented in the context of the HNM (harmonic+noise model) system, which allows high-quality modifications of speech signals. Compared to earlier methods based on vector quantization, the proposed conversion scheme results in a much better match between the converted envelopes and the target envelopes. Evaluation by objective tests and formal listening tests shows that the proposed transform greatly improves the quality and naturalness of the converted speech signals compared with previous proposed conversion methods.

Hidden structure in liquids

Abstract: The canonical partition function for classical many-body systems is transformed so that the temperature-independent packing statistics and the thermal excitations are uniquely separated. This requires classification of particle configurations according to multidimensional potential-energy minima that can be reached by steepest-descent paths ("quenches"). Such classifications have been constructed for several starting configurations in the solid, fluid, and coexistence phases of the two-dimensional Gaussian core model. These quenches reveal a remarkable degree of polycrystalline order hidden within the fluid phase by "vibrational" distortion, and that order appears to have a large correlation length. The results suggest that melting hinges upon defect softening in the quenched packings, and a crude "theory" of melting for the Gaussian core model is developed in the Appendix.

Car-Parrinello Molecular-Dynamics with Vanderbilt Ultrasoft Pseudopotentials

Abstract: We show how the ultrasoft pseudopotentials which have recently been proposed by Vanderbilt can be implemented efficiently in the context of Car-Parrinello molecular-dynamics simulations We address the differences with respect to the conventional norm-conserving schemes, identify certain problems which arise, and indicate how these problems can be overcome This scheme extends the possibility of performing first-principles molecular dynamics to systems including first-row elements and transition metals