一种高效的MIMO-OFDM预编码实现方法

现有的预编码码本设计方法均导致了在信道量化时计算复杂度过高的问题。本文研究了Kerdock码本,这种码本由多个相互无偏基矩阵组成,这些基矩阵都只含有4个已知元素且都是归一化矩阵,并基于Kerdock码本的这种特殊结构给出了一种高效的实现方法。本文将在信道量化部分详细讲解这种实现的具体结构。这种结构有利于降低搜索复杂度,从仿真和计算结果可以看出采用这种结构的码本和量化器,能以很小的性能损失换来计算复杂度降低一半的优越性。     

一种MIMO系统自适应码本设计方法

提出一种基于码本旋转的自适应码本设计方法,在不改变现有的码本基础矩阵的基础上,根据误码率(BER)和信干噪比(SINR)的统计和估计结果,生成一组新的旋转矩阵码本,并结合反馈开销考虑与原来基础码本矩阵构成双码本矩阵,根据信道的实时变化及时地调整码本的精度,从而能够在有限反馈的情况下更加有效地提高预编码的性能。     

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.     

Fast Image Coding Algorithm Using Indirect-Index Codebook Based on SMVQ

Side-match vector quantization (SMVQ) achieves better compression performance than vector quantization (VQ) in image coding due to its exploration of the dependence of adjacent pixels. However, SMVQ has the disadvantage of requiring excessive time during the process of coding. Therefore, this paper proposes a fast image coding algorithm using indirect-index codebook based on SMVQ (ⅡC-SMVQ) to reduce the coding time. Two codebooks, named indirect-index codebook (Ⅱ-codebook) and entire-state codebook (ES-codebook), are trained and utilized. The Ⅱ-codebook is trained by using the Linde-Buzo-Gray (LBG) algorithm from side-match information, while the ES-codebook is generated from the clustered residual blocks on the basis of the Ⅱ-codebook. According to the relationship between these two codebooks, the codeword in the Ⅱ-codebook can be regarded as an indicator to construct a fast search path, which guides in quickly determining the state codebook from the ES-codebook to encode the to-be-encoded block. The experimental results confirm that the coding time of the proposed scheme is shorter than that of the previous SMVQ.     

LTE基于码本选择预编码研究

本文研究了LTE系统中基于码本选择的预编码发送方案,对LTE基于码本选择的预编码方案进行了推导,提出了基于性干比（SINR）的码本选择算法,并对其进行了性能仿真。仿真结果表明,在4根发射天线和2根接收天线配置下,基于码本的预编码简单实用,且能够在在满足LTE性能需求的基础上大大提高系统性能。     

基于BD-DFT扩展的大规模MIMO码本设计

考虑到大规模多输入多输出（Multiple Input Multiple Output, MIMO）阵列尺寸及外形等因素的限制,本文提出了一种适用于基站采用交叉极化天线面阵的大规模MIMO（Massive MIMO）码本设计方法。该方法综合考虑交叉极化信道的对角化特点和相邻天线之间的相关性,首先设计出与采用交叉极化线阵匹配的码本,进而利用垂直维度天线间的相关性对其进行扩展,最终生成与交叉极化面阵相匹配的码本。仿真结果表明该码本设计方法可使大规模MIMO系统的传输速率和误码率性能得到明显地提升。     

二维网格编码矢量量化及其在静止图像量化中的应用

该文提出了在二维码书空间中，在矢量量化（VQ）的基础上，应用网格编码量化（TCQ）的思想来实现量化的新方法－－二维网格编码矢量量化（2D－TCVQ）。该方法首先把小码书扩展成大的虚码书，然后用网格编码矢量量化（TCVQ）的方法在扩大的二维码书空间中用维物比算法来寻找最佳量化路径。码书扩大造成第一子集最小失真减小从提高了量化性能。由于二维TCVQ采用的码书尺寸较小，因而可以应用到低存贮、低功耗的编解码环境。仿真结果表明，同一码书尺寸下，二维TCVQ比TCVQ好0．5dB左右。同时，该方法具有计算量适中，解码简单以及对误差扩散不敏感的优点。     

Fast codebook searching in a SOM-based vector quantizer for image compression

We propose a novel method for fast codebook searching in self-organizing map (SOM)-generated codebooks. This method performs a non-exhaustive search of the codebook to find a good match for an input vector. While performing an exhaustive search in a large codebook with high dimensional vectors, the encoder faces a significant computational barrier. Due to its topology preservation property, SOM holds a good promise of being utilized for fast codebook searching. This aspect of SOM remained largely unexploited till date. In this paper we first develop two separate strategies for fast codebook searching by exploiting the properties of SOM and then combine these strategies to develop the proposed method for improved overall performance. Though the method is general enough to be applied for any kind of signal domain, in the present paper we demonstrate its efficacy with spatial vector quantization of gray-scale images.     

一种基于优先树脉冲取代的固定码本搜索方法

分析了G.722.2中的固定码本结构及其搜索方法,结合深度优先树与脉冲取代法各自的优点,提出了一种新的方法——基于优先树脉冲取代的固定码本搜索方法,该方法在基本保持语音质量的前提下,可使固定码本搜索计算复杂度降低,从而使G.722.2的编码运行时间进一步减少。实验结果表明,与G.722.2中采用的深度优先树搜索方法相比,基于优先树脉冲取代的固定码本搜索方法可以在不影响语音质量的前提下,使固定码本搜索复杂度降低85%以上。     

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。     

G.729自适应码书搜索算法的研究

G.729语音编码算法复杂,很大程度上要归因于码书搜索算法。为了降低码书搜索复杂度,G.729的简化版G.729A采用了自适应码书的偶样点开环基音搜索,使得编码复杂度大为降低,不过编码仍要花费很多的时间。通过对G.729码书搜索算法的研究,提出了对自适应码书的改进。改进了自适应码书搜索的G.729编码语音质量不低于G.729A的语音质量,但自适应搜索复杂度大大降低。     

一种基于码本轮转的有限反馈量化方法

大规模多输入多输出（Multiple-Input Multiple-Output,MIMO）系统中随着天线数目的增加,其反馈比特数将随之大幅度增加。为此,提出了一种基于码本轮转的有限反馈量化方法。该方法中,用户在前一时刻得到最佳码字之后,在码本中选取轮转区域构成虚拟码本,判断当前时刻的信道向量,满足轮转条件的用户将虚拟码本轮转到码本起始位置,在虚拟码本中进行量化;不满足轮转条件的用户在原始码本中进行量化,选出当前时刻的最优码字。反馈比特数分析与仿真结果表明,所提方法可轮转的虚拟码本减少了量化码字的数量,从而减少了反馈比特数,是系统性能与反馈比特数的一种折中。     

Performance comparisons between PCA-EA-LBG and PCA-LBG-EA approaches in VQ codebook generation for image compression

The aim of this study is to generate vector quantisation (VQ) codebooks by integrating principle component analysis (PCA) algorithm, Linde-Buzo-Gray (LBG) algorithm, and evolutionary algorithms (EAs). The EAs include genetic algorithm (GA), particle swarm optimisation (PSO), honey bee mating optimisation (HBMO), and firefly algorithm (FF). The study is to provide performance comparisons between PCA-EA-LBG and PCA-LBG-EA approaches. The PCA-EA-LBG approaches contain PCA-GA-LBG, PCA-PSO-LBG, PCA-HBMO-LBG, and PCA-FF-LBG, while the PCA-LBG-EA approaches contain PCA-LBG, PCA-LBG-GA, PCA-LBG-PSO, PCA-LBG-HBMO, and PCA-LBG-FF. All training vectors of test images are grouped according to PCA. The PCA-EA-LBG used the vectors grouped by PCA as initial individuals, and the best solution gained by the EAs was given for LBG to discover a codebook. The PCA-LBG approach is to use the PCA to select vectors as initial individuals for LBG to find a codebook. The PCA-LBG-EA used the final result of PCA-LBG as an initial individual for EAs to find a codebook. The search schemes in PCA-EA-LBG first used global search and then applied local search skill, while in PCA-LBG-EA first used local search and then employed global search skill. The results verify that the PCA-EA-LBG indeed gain superior results compared to the PCA-LBG-EA, because the PCA-EA-LBG explores a global area to find a solution, and then exploits a better one from the local area of the solution. Furthermore the proposed PCA-EA-LBG approaches in designing VQ codebooks outperform existing approaches shown in the literature.     

Codebook‐Based Precoding for SDMA‐OFDMA with Spectrum Sharing

This paper focuses on codebook‐based precoding for space‐division multiple access/orthogonal frequency‐division multiple access (SDMA‐OFDMA) systems aiming to guarantee high throughput for their users as well as to mitigate interference to fixed satellite service (FSS). A systematic design of SDMA codebook for subband‐based OFDMA is proposed, which forms multiple orthogonal beams with common spatial null in the direction of a victim FSS earth station (ES). The design enables both transmitter and receiver to independently construct identical codebook by sharing only on the direction angle of an FSS ES, which takes fewer overhead bits than Gram‐Schmidt process, a general method satisfying our design criterion. A system‐level throughput evaluation shows that the proposed precoding provides superior performance over existing spectrum sharing method, that is, subband deactivation. The spectrum sharing analysis shows that the proposed precoding, even with an estimation error of the direction angles of an FSS ES, causes lower interference than existing precoding, knockdown precoding.     

Transmission Scheme for 2D Antenna Array MIMO Systems with Limited Feedback

Three-dimensional (3D) multiple-input multiple-output (MIMO) systems exploit spatial richness and provide another degree of freedom to transmit signals and eliminate spatial interference. Currently, however, there is no 3D codebook for two-dimensional (2D) antenna array MIMO systems with limited feedback. In this paper, based on the existing 2D codebook, we present a limited feedback and transmission scheme for 2D antenna array MIMO systems. In this scheme, the mobile station (MS) has imperfect channel knowledge, and the base station (BS) only acquires partial information relating the channel instantiation. MS must feed back two channel state information (CSI) instances, i.e., the horizontal and vertical CSIs. After receiving the two CSI instances, the BS interpolates a new vertical precoding vector using the vertical CSI. Then, the BS re-constructs a 3D beamforming vector using horizontal and vertical precoding vectors and compensates the reported horizontal channel quality indicator. System level simulation is employed, and the simulation results show that the proposed method improves the system spectral efficiency and the cell-edge SE significantly.     

Labeling-based Zero-forcing Beamforming for LTE MU-MIMO

提出了一种聪明的TD-LTE MIMO操作模式,它结合了波束成形技术和闭环反馈MIMO的优点。当eNB获得UE上行SRS参考信号的信道信息,L1进行基于码本的信道估计量化和标签化。L1将标签上传到L2,L2基于标签进行多用户调度,这样较好地解决了基于迫零的UE配对和L1/L2间跨层资源分配这两个问题。 L1无需更多计算便可生成波束成形的预编码矩阵。同时,提出了在可接受的次优性能下一种易实现的一般性框架。为了达到目标,给出了新的码本设计标准和快速预编码矩阵的生成算法。     

毫米波MIMO系统中基于正交码本的模数混合预编码算法

由于毫米波混频器件的高成本和高功耗,传统MIMO系统的数字预编码技术面临硬件复杂度过高的缺点,因而模数混合预编码吸引了学术界和工业界的广泛关注.基于此,提出了一种基于正交码本的模数混合预编码算法,该算法利用模拟波束成形码本的正交性,并行地设计各个射频链路的波束成形向量,显著降低了传统混合预编码设计中正交匹配追踪算法的计算复杂度,从而降低了硬件实现的复杂度.     

Linearly constrained generalized Lloyd algorithm for reducedcodebook vector quantization

As linearly constrained vector quantization (LCVQ) is efficient for block-based compression of images that require low complexity decompression, it is a “de facto” standard for three-dimensional (3-D) graphics cards that use texture compression. Motivated by the lack of an efficient algorithm for designing LCVQ codebooks, the generalized Lloyd (1982) algorithm (GLA) for vector quantizer (VQ) codebook improvement and codebook design is extended to a new linearly constrained generalized Lloyd algorithm (LCGLA). This LCGLA improves VQ codebooks that are formed as linear combinations of a reduced set of base codewords. As such, it may find application wherever linearly constrained nearest neighbor (NN) techniques are used, that is, in a wide variety of signal compression and pattern recognition applications that require or assume distributions that are locally linearly constrained. In addition, several examples of linearly constrained codebooks that possess desirable properties such as good sphere packing, low-complexity implementation, fine resolution, and guaranteed convergence are presented. Fast NN search algorithms are discussed. A suggested initialization procedure halves iterations to convergence when, to reduce encoding complexity, the encoder considers the improvement of only a single codebook for each block. Experimental results for image compression show that LCGLA iterations significantly improve the PSNR of standard high-quality lossy 6:1 LCVQ compressed images     

Dynamically restricted codebook-based vector quantisation scheme for mesh geometry compression

The transmission and storage of large amounts of vertex geometry data are required for rendering geometrically detailed 3D models. To alleviate bandwidth requirements, vector quantisation (VQ) is an effective lossy vertex data compression technique for triangular meshes. This paper presents a novel vertex encoding algorithm using the dynamically restricted codebook-based vector quantisation (DRCVQ). In DRCVQ, a parameter is used to control the encoding quality to get the desired compression rate in a range with only one codebook, instead of using different levels of codebooks to get different compression rate. During the encoding process, the indexes of the preceding encoded residual vectors which have high correlation with the current input vector are prestored in a FIFO so that both the codevector searching range and bit rate are averagely reduced. The proposed scheme also incorporates a very effective Laplacian smooth operator. Simulation results show that for various size of mesh models, DRCVQ can reduce PSNR degradation of about 2.5–6 dB at 10 bits per vertex comparative to the conventional vertex encoding method with stationary codebooks and, DRCVQ with arithmetic coding of codevector indexes and Laplacian smoothener can outperform the state-of-art Wavemesh for non-smooth meshes while performing slightly worse for smooth meshes. In addition, we use MPS as codevector search acceleration scheme so that the compression scheme is real-time.     

基于改进禁止搜索算法的矢量量化码书设计

本文提出了基于改进禁止搜索(TS)算法的矢量量化(VQ)码书设计方法.禁止搜索算法的关键是如何定义一个解以及如何在当前解的基础上生成邻域解.由于码书设计的两个优化准则是最邻近条件和聚类质心条件,本文提出了两种禁止搜索算法的解描述方案,其相应算法分别叫基于码书的禁止搜索(CB-TS)算法和基于聚类划分的禁止搜索(PB-TS)算法.为了提高禁止搜索算法的性能,文中在禁止搜索算法中融入了模拟退火(SA)机制.为了进一步提高码书性能,文中还将码书设计的传统LBG算法融入禁止搜索算法中.结果表明,基于禁止搜索的两种码书设计方案所生成的码书性能都比LBG算法有明显提高.