Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Research Article Using Geometrical Properties for Fast Indexation of Gaussian Vector Quantizers | Hindawi Publishing Corporation EURASIP Journal on Advances in Signal Processing Volume 2007 Article ID 63192 11 pages doi 2007 63192 Research Article Using Geometrical Properties for Fast Indexation of Gaussian Vector Quantizers E. A. Vassilieva D. Krob and J. M. Steyaert Laboratoire d Informatique de l Ecole Polytechnique LIX Ecole Polytechnique 91128 Palaiseau Cedex France Received 2 November 2005 Revised 26 August 2006 Accepted 10 September 2006 Recommended by Satya Dharanipragada Vector quantization is a classical method usedin mobile communications. Each sequence of d samples of the discretized vocal signal is associated to the closest d-dimensional codevector of a given set called codebook. Only the binary indices of these codevectors the codewords are transmitted over the channel. Since channels are generally noisy the codewords received are often slightly different from the codewords sent. In order to minimize the distortion of the original signal due to this noisy transmission codevectors indexed by one-bit different codewords should have a small mutual Euclidean distance. This paper is devoted to this problem of index assignment of binary codewords to the codevectors. When the vector quantizer has a Gaussian structure we show that a fast index assignment algorithm based on simple geometrical and combinatorial considerations can improve the SNR at the receiver by 5dB with respect to a purely random assignment. We also show that in the Gaussian case this algorithm outperforms the classical combinatorial approach in the field. Copyright 2007 E. A. Vassilieva et al. This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited. 1. INTRODUCTION Taking into account the constraints of the transmission channel between the base transceiver stations BTS and mobile stations MS voice is coded in mobile networks .
