Codebook

About: Codebook is a research topic. Over the lifetime, 8492 publications have been published within this topic receiving 115995 citations.

Fast three‐dimensional data compression of hyperspectral imagery using vector quantization with spectral‐feature‐based binary coding

Abstract: A fast lossy 3-D data compression scheme using vector quantization (VQ) is presented that exploits the spatial and the spectral redundancy in hyperspectral imagery. Hyperspectral imagery may be viewed as a 3-D array of samples in which two dimensions correspond to spatial position and the third to wavelength. Unlike traditional 2-D VQ, where spatial blocks of n3m pixels are taken as vectors, we define one spectrum, corresponding to a profile taken along the wavelength axis, as a vector. This constitution of vectors makes good use of the high corre- lation in the spectral domain and achieves a high compression ratio. It also leads to fast codebook generation and fast codevector matching. A coding scheme for fast vector matching called spectral-feature-based binary coding (SFBBC) is used to encode each spectral vector into a simple and efficient set of binary codes. The generation of the codebook and the matching of codevectors are performed by matching the binary codes produced by the SFBBC. The experiments were carried out using a test hyperspectral data cube from the Compact Airborne Spectro- graphic Imager. Generating a codebook is 39 times faster with the SF- BBC than with conventional VQ, and the data compression is 30 to 40 times faster. Compression ratios greater than 192 : 1 have been achieved with peak signal-to-noise ratios of the reconstructed hyper- spectral sequences exceeding 45.2 dB. © 1996 Society of Photo-Optical Instru- mentation Engineers.

Efficient codebook-based MIMO beamforming for millimeter-wave WLANs

Abstract: Beamforming is a critical and natural solution for 60 GHz band wireless communications due to the increased signal attenuation. In this paper we propose an efficient codebook-based MIMO beamforming training scheme for estimating the antenna weight vectors (AWVs) in millimeter-wave wireless local area networks (WLANs). We adopt the discrete Fourier transform (DFT)-based codebooks. We propose a simple and efficient iterative AWVs training algorithm that uses only one AWV feedback to obtain the best transmit (TX) and receive (RX) AWVs pair. Instead of initial selection of multiple TX and RX AWVs in the IEEE 802.11ad draft standard, we only select the best TX AWV and RX AWV for subsequent refinement. The beam pattern search for refinement is limited only to the region corresponding to the best TX AWV and RX AWV from initial selection and their angular rotated adjacent beams. To verify the performance we compare our proposed scheme with the one specified in the IEEE 802.11ad in terms of the beam gains and show that our proposed scheme outperforms the one in the IEEE 802.11ad even using the fewer beamforming training time.

Codes with bounded synchronization delay

Abstract: In this paper we study “bounded delay codes,≓ which have the property that every message can be uniquely decoded by examining a segment of bounded length, from any starting point. This class is shown to attain the upper bound on codebook size previously encountered (but not always attained) for the familiar subclass of “comma-free codes.≓ The problem of determining the smallest message length s0 which guarantees unique decipherability for such codes is discussed. The bounded delay codes are classified according to the value of s0. An extension is made to the case of variable length codes, in which the upper bound formula of the uniform word-length case is replaced by a system of inequalities.

Gain-Adaptive Vector Quantization with Application to Speech Coding

Abstract: The generalization of gain adaptation to vector quantization (VQ) is explored in this paper and a comprehensive examination of alternative techniques is presented. We introduce a class of adaptive vector quantizers that can dynamically adjust the "gain" or amplitude scale of code vectors according to the input signal level. The encoder uses a gain estimator to determine a suitable normalization of each input vector prior to VQ encoding. The normalized vectors have reduced dynamic range and can then be more efficiently coded. At the receiver, the VQ decoder output is multiplied by the estimated gain. Both forward and backward adaptation are considered and several different gain estimators are compared and evaluated. Gain-adaptive VQ can be used alone for "vector PCM" coding (i.e., direct waveform VQ) or as a building block in other vector coding schemes. The design algorithm for generating the appropriate gain-normalized VQ codebook is introduced. When applied to speech coding, gain-adaptive VQ achieves significant performance improvement over fixed VQ with a negligible increase in complexity.

Codebook design method for multiple input multiple output system and method for using the codebook

Abstract: A multiple input multiple output (MIMO) communication method using a codebook is provided The MIMO communication method may use one or more codebooks and the codebooks may change according to a transmission rank, a channel state of a user terminal, and/or a number of feedback bits The one or more codebooks may be adaptively updated according to a time correlation coefficient of a channel