SCMA codebook design based on resource block constellation

Aiming at the problems of typical sparse code multiple access codebook design scheme based on multidimensional mother constellation that the complexity is high and the minimum Euclidean distance between constellation points on resource blocks is difficult to determine,a SCMA codebook design scheme based on resource block constellation was proposed.By converting the design of multidimensional mother constellation into the design of two-dimensional resource block constellation,the design complexity of constellation was reduced.And the codebook design scheme starting from resource block constellation could maximize the minimum Euclidean distance between constellation points on resource blocks,which was better than the design method in which user codebooks were obtained from multi-dimensional mother constellation.Simulation results show that the proposed SCMA codebook design scheme based on resource block constellation can significantly improve the BER performance of system compared with the typical codebook design scheme based on multidimensional mother constellation.     

On the performance and complexity of channel-optimized vectorquantizers

The performance and complexity of channel-optimized vector quantizers are studied for the Gauss-Markov source. Observations on the geometric structure of these quantizers are made, which have an important implication on the encoding complexity. For the squared-error distortion measure, it is shown that an operation equivalent to a Euclidean distance measurement with respect to an appropriately defined set of points (used to identify the encoding regions) can be used to perform the encoding. This implies that the encoding complexity is proportional to the number of encoding regions. It is then demonstrated that for very noisy channels and a heavily correlated source, when the codebook size is large, the number of encoding regions is considerably smaller than the codebook size-implying a reduction in encoding complexity     

一种构造BCM码的新方法

由Imai与Hirakawa提出的多级编码方法,可用来构造具有任意大最小平方欧氏距离的分组调制(BCM)码.一个BCM码的性能主要取决于构成它的各个成分码,恰当地选择成分码是构造一个好的BCM码的关键.文章给出了一种新方法,通过选用不同长度的成分码来构造BCM码.仿真结果表明用此方法构造出的BCM码较传统的BCM码在性能与复杂度上有明显的改善.     

A new dynamic finite-state vector quantization algorithm for imagecompression

The picture quality of conventional memory vector quantization techniques is limited by their supercodebooks. This paper presents a new dynamic finite-state vector quantization (DFSVQ) algorithm which provides better quality than the best quality that the supercodebook can offer. The new DFSVQ exploits the global interblock correlation of image blocks instead of local correlation in conventional DFSVQs. For an input block, we search the closest block from the previously encoded data using the side-match technique. The closest block is then used as the prediction of the input block, or used to generate a dynamic codebook. The input block is encoded by the closest block, dynamic codebook or supercodebook. Searching for the closest block from the previously encoded data is equivalent to expand the codevector space; thus the picture quality achieved is not limited by the supercodebook. Experimental results reveal that the new DFSVQ reduces bit rate significantly and provides better visual quality, as compared to the basic VQ and other DFSVQs.     

An Efficient Algorithmic Lower Bound for the Error Rate of Linear Block Codes

We present an efficient algorithmic lower bound for the block error rate of linear binary block codes under soft maximum-likelihood decoding over binary phase-shift keying modulated additive white Gaussian noise channels. We cast the problem of finding a lower bound on the probability of a union as an optimization problem that seeks to find the subset that maximizes a recent lower bound - due to Kuai, Alajaji, and Takahara - that we will refer to as the KAT bound. The improved bound, which is denoted by LB-s, is asymptotically tight [as the signal-to-noise ratio (SNR) grows to infinity] and depends only on the code's weight enumeration function for its calculation. The use of a subset of the codebook to evaluate the LB-s lower bound not only significantly reduces computational complexity, but also tightens the bound specially at low SNRs. Numerical results for binary block codes indicate that at high SNRs, the LB-s bound is tighter than other recent lower bounds in the literature, which comprise the lower bound due to Seguin, the KAT bound (evaluated on the entire codebook), and the dot-product and norm bounds due to Cohen and Merhav.     

基于二维格星座对SCMA码本的一种设计方法

现有的SCMA(稀疏码分多址)码本采用高维复数星座和映射矩阵相结合的设计方法,存在高维复数星座设计过程复杂,且任意时频资源星座图星座点间的最小欧式距离难以控制的问题。针对上述问题提出了一种基于时频资源星座的码本设计方法。首先设计一个二维格星座,然后通过星座优化和扩频得到特定用户的码本。所提方法不仅可以获得最大成形增益和最大最小欧式距离的合成星座图,还能使SCMA系统性能随着码本维度的增加而提升。仿真结果表明:在高斯信道下,提出的码本较现有的码本有效提升了系统性能。     

A fuzzy classified vector quantizer for image coding

Vector quantization of images raises problems of complexity in codebook search and subjective quality of images. The family of image vector quantization algorithms proposed in this paper addresses both of those problems. The fuzzy classified vector quantizer (FCVQ) is based on fuzzy set theory and consists basically in a method of extracting a subcodebook from the original codebook, biased by the features of the block to be coded. The incidence of each feature on the blocks is represented by a fuzzy set that captures its (possibly subjective) nature. Unlike the classified vector quantizer (CVQ), in the FCVQ a specific subcodebook is extracted for each block to be coded, allowing a better adaptation to the block. The CVQ may be regarded as a special case of the FCVQ. In order to explore the possible correlation between blocks, an estimator for the degree of incidence of features on the block to be coded is included. The estimate is based on previously coded blocks and is obtained by maximizing a possibility; a distribution that intends to represent the subjective knowledge on the feature's possibility of occurrence conditioned to the coded blocks is used. Some examples of the application of a FCVQ coder to two test images are presented. A slight improvement on the subjective quality of the coded images is obtained, together with a significant reduction on the codebook search complexity and, when applying the estimator, a reduction of the bit rate     

Wavelet-based image coding using nonlinear interpolative vectorquantization

We propose a reduced complexity wavelet-based image coding technique. Here, 64-D (for three stages of decomposition) vectors are formed by combining appropriate coefficients from the wavelet subimages, 16-D feature vectors are then extracted from the 64-D vectors on which vector quantization (VQ) is performed. At the decoder, 64-D vectors are reconstructed using a nonlinear interpolative technique. The proposed technique has a reduced complexity and has the potential to provide a superior coding performance when the codebook is generated using the training vectors drawn from similar images.     

On multilevel block modulation codes

The multilevel technique for combining block coding and modulation is investigated. A general formulation is presented for multilevel modulation codes in terms of component codes with appropriate distance measures. A specific method for constructing multilevel block modulation codes with interdependency among component codes is proposed. Given a multilevel block modulation code C with no interdependency among the binary component codes, the proposed method gives a multilevel block modulation code C' that has the same rate as C, a minimum squared Euclidean distance not less than that of C, a trellis diagram with the same number of states as that of C, and a smaller number of nearest neighbor codewords than that of C . Finally, a technique is presented for analyzing the error performance of block modulation codes for an additive white Gaussian noise (AWGN) channel based on soft-decision maximum likelihood decoding. Error probabilities of some specific codes are evaluated by simulation and upper bounds based on their Euclidean weight distributions     

An on-line universal lossy data compression algorithm viacontinuous codebook refinement. II. Optimality for phi-mixing sourcemodels

For pt.I see ibid., vol.42, no.3, p.803-21 (1996). Two versions of the gold-washing data compression algorithm, one with codebook innovation interval and the other with finitely many codebook innovations, are considered. The version of the gold-washing algorithm with codebook innovation interval k is a variant of the gold-washing algorithm such that the codebook is innovated once every k+1 source words during the process of encoding the entire source. It is demonstrated that when this version of the gold-washing algorithm is applied to encode a stationary, φ-mixing source, the expected distortion performance converges to the distortion rate function of the source as the codebook length goes to infinity. Furthermore, if the source to be encoded is a Markov source or a finite-state source, then the corresponding sample distortion performance converges almost surely to the distortion rate function. The version of the gold-washing algorithm with finitely many codebook innovations is a variant of the gold-washing algorithm in which after finitely many codebook innovations, the codebook is held fixed and reused to encode the forthcoming source sequence block by block. Similar results are shown for this version of the gold-washing algorithm. In addition, the convergence speed of the algorithm is discussed     

一种快速模糊矢量量化图像编码算法

本文在学习矢量量化和模糊矢量量化算法的基础上,设计了一种新的训练矢量超球体收缩方案和码书学习公式,提出了一种快速模糊矢量量化算法。该算法具有对初始码书选取信赖性小,不会陷入局部最小和运算最小的优点。实验表明,ＦＦＶＱ设计的图像码书性能与ＦＶＡ算法相比,训练时间大大缩短,峰值信噪比也有改善。     

Grassmannian流形上基于高分辨率动态聚焦码本的MIMO信道预测

针对MIMO时变信道下,有限反馈发射预编码存在反馈延迟的问题,提出将多数据流空间复用传输的MIMO信道的主右奇异矩阵的列空间建模于n维复欧氏空间上p维子空间的集合Grassmannian流形Gn,p上,利用Grassmannian流形的测地线对时变信道进行跟踪预测,以补偿反馈延迟对于系统性能的影响。在此基础上,从Grassmannian流形的几何特性入手,针对Grassmannian流形的切空间提出了一种高分辨率动态聚焦的多维切空间码本。计算机仿真表明,Grassmannian流形上基于高分辨率动态聚焦码本的有限反馈预测预编码的系统性能明显优于存在反馈延迟的无记忆有限反馈预编码和采用固定码本的有限反馈预测预编码。      

Parallel VQ compression using PNN algorithm for PC Grid system

PC Grid is a promising platform to achieve a high performance computing with less construction cost. A kind of parameter sweep applications (PSA) can be efficiently carried out on the PC Grid, but there exist parallel applications are not suitable for it. We focus on PNN (Pairwise Nearest Neighbor) codebook generation algorithm for the VQ compression algorithm and propose a parallel version of the PNN algorithm suitable for the PC Grid, called “One-step Grid PNN”, as well as “multi-step Grid PNN”, which reduces the computation complexity on a master computer. The Grid PNN is a modified version of the PNN algorithm that creates a different codebook than the original PNN does, thus the quality of a codebook created by using the Grid PNN may be worse than that of a codebook by the original PNN. However, our experimental results show that the quality of the codebook is almost same as that of the original one. We also confirm the effectiveness of the one-step and multi-step Grid PNN by the evaluation of the computational complexity of the algorithm and experiments executed on a PC cluster system.     

Difference set codes: codes with squared Euclidean distance of sixfor partial response channels

We present a new construction of block codes for the (1-D)-PR (partial response) channel. The codewords in the code correspond to constant-sum subsets of a difference set. It is shown that at the output of a noiseless (1-D)-PR channel; the minimum squared Euclidean distance of such a code is at least six, compared to two for the uncoded system. This construction yields larger code rates than previously known codes with the same minimum distance for large code lengths. The construction technique also imposes upper bounds on the decoding complexity of the codes     

一种新的语音LSF矢量量化码书优化算法

LSF(线谱频率)码书的性能对合成语音质量有着重要影响.经典的LBG算法容易陷入局部最优,而目前的一些码书进化算法搜索空间较大、搜索效率不明显.本文提出了一种新型的基于对LSF矢量空间进行拉伸变化的混合进化码书优化算法.该算法编码空间与矢量同维,相对较小,便于优化操作.算法中引入EP中的变异操作对PSO位置、速度矢量进行控制,以提高优化搜索算法的效率.实验结果表明,本文算法有效地改善了码书性能.     

CELP中的“线性移位”随机码本的研究

随机码本是码本激励线性预测ＣＥＬＰ声码器的一个重要组成部分,其码本结构及其相应的搜索算法直接影响着语音编译码系统的语音质量和实时实现。本文给出了一个结构化随机码本－“线性移位”高斯码本的一组双向递归计算公式,由此提出了一种单向递归搜索算法,从而有效地降低了随机码本的搜索复杂度,使搜索速度较之参考文献给出的原随机码本搜索法提高１．７６倍,为进一步减少码本搜索的运算量,本文还引入了局部搜索的次优化准则     

A bit-level systolic architecture for implementing a VQ tree search

A bit-level systolic array system for performing a binary tree Vector Quantization codebook search is described. This consists of a linear chain of regular VLSI building blocks and exhibits data rates suitable for a wide range of real-time applications. A technique is described which reduces the computation required at each node in the binary tree to that of a single inner product operation. This method applies to all the common distortion measures (including the Euclidean distance, the Weighted Euclidean distance and the Itakura-Saito distortion measure) and significantly reduces the hardware required to implement the tree search system.     

Double Codebook Beamforming Technique in Massive MIMO

In order to adapt double codebook beamforming technique in massive MIMO system, double codebook estimation algorithms based on the extended double codebook are proposed in this paper, such as one-dimensional (1D) estimation inherited MIMO, independent two-dimensional (2D) estimation and ESPRIT-like estimation. 1D estimation traverses the candidates based on the cross combination of two directions. Independent 2D estimation traverses the candidates based on two directions separately.  ESPRIT-like estimation is based on rotational invariance principle of antenna array, which imposes significantly lower computational complexity than the former two algorithms. Advanced, its complexity does not increase with the number of candidates. Finally, the complexity and system performance with three algorithms are compared and analyzed. The results show that 1D estimation gains the best performance, but it is too complex and difficult for practical implementation. ESPRIT-like estimation is more practical due to its reduced complexity and comparable performance with the independent 2D estimation algorithm, especially with small number of candidates.