电力线载波通信中减小PAPR的预编码方法

为了提高电力线载波通信的可靠性和有效性,提出一种在发送设备端进行的信号处理方法,即相位调整预编码方法。利用了发送多个载波信号相位改变的不同,可以改变多个载波信号叠加功率和,从而减少电力线载波通信的峰均比。分析了峰均比形成的原因,提出了以最小化发送功率为目标函数,求解每个载波发送相位的优化问题。仿真结果表明,该预编码方法能够有效抑制电力线载波通信中过高的峰均比问题,在不增加复杂度的前提下,有效提高了通信的可靠性,证明了该方法的正确性和有效性。     

动态网络下交替优化正交匹配追踪混合预编码

为解决毫米波大规模多输入多输出(multiple input multiple output, MIMO)系统中混合预编码频谱性能损失严重的问题,本文提出了一种动态网络下交替优化正交匹配追踪混合预编码算法。首先,通过恒模约束条件下的模拟预编码矩阵确定固定相位移相器与天线之间较好的初始连接状态,以提高迭代收敛速率;然后,根据连接状态构造最佳候选模拟预编码矩阵,从而求解全局最优的索引向量;最后,由最优索引向量组成的数字预编码矩阵反馈到动态网络,可动态实现移相器与天线阵列连接状态的交替优化更新。同时,所提出的算法只需要少量固定相位的移相器,在频谱性能和复杂度之间达到良好平衡。仿真结果表明,与其他现有算法相比,该算法具有更高频谱效率、更高迭代收敛速率和更低复杂度,特别是当射频链路数大于数据流数时,频谱效率的提升更加显著。     

面向需求响应业务的灵活弹性传输策略

随着需求响应(demand response,DR)不断深化实践,未来需要依靠高可靠的信息交互支撑精细化的DR控制.然而在DR无线通信场景下,复杂的信道环境极大影响DR高效的信息交互,现有技术难以匹配和满足DR业务的特性.针对DR无线传输中的信道质量问题,设计了面向DR业务的灵活弹性传输策略,该策略通过自适应编码实现....     

算术熵编码CABAC

文中研究基于上下文的自适应二进制算术熵编码(CABAC),并对其计算复杂度进行了深入的分析.CABAC被新一代视频编码标准H.264所采用,使得H.264的压缩性能得到极大提升.     

预编码方案多天线超宽带系统误码率性能计算

多天线技术引入超宽带系统是提高传输质量和抗干扰能力、降低误比特率(BER)的有效方法之一。然而,随着天线数目的增加,硬件成本也随之提高。天线选择技术和优化发射功率能降低硬件成本、复杂度及提高系统性能。若已知全部的发射端信道状态信息(CSI),提出了最大比率发射(MRT)技术和发射天线选择(TAS)技术相结合的超宽带系统。基于信道功率增益最大的天线选择准则,系统选择较好的天线子集(MT ,2;MR )工作,并采用 MRT技术优化分配所选择的双天线发射功率。仿真结果表明：结合MRT和 TAS技术的超宽带系统的误比特率性能都得到了明显改善。     

基于AVS的变电站远程视频监控系统

AVS是我国具有自主知识产权的视频编码标准,其性能基本上与H.264持平,而实现成本和算法(以及芯片)复杂度却大大低于H.264,具有较高的性价比.文章探讨将AVS标准引入变电站视频监控中,实现AVS视频编码技术对视频图像的压缩、传输和解压缩等功能,内容涉及系统的结构设计、传输控制方案、AVS编解码标准的运用等问题.对变电站视频监控系统的改革带来的优越性进行了详尽地描述.     

基于ZF准则的MU-MIMO下行链路联合预编码算法

多用户MIMO技术利用空间多址接入技术（SDMA）能够在相同时频资源上传送多个用户的信息,能够显著提高多用户分集增益,但由于多个用户占据相同的时频资源,系统中存在着用户间及用户自身天线间的干扰,经典的迫零算法可有效消除用户自身天线间的干扰,并不能消除用户间的干扰.结合联合预编码算法,对经典迫零算法进行了改进,同时针对系统中仍存在残存干扰的问题,引入了一个预滤波系数,使得改进的算法可以同时消除用户间及用户自身天线间的干扰.通过搭建系统级仿真平台验证在同一信噪比下,改进的算法相对基于ZF准则的预编码算法提高了系统容量,降低了系统误码率.     

面向需求响应业务传输的预编码优化技术

随着需求侧管理领域的快速发展和信息化水平的提升,越来越多的需求响应(demand response,DR)终端将会接入电网.作为靠近用户的末端设备,现有的需求响应终端在信息处理方面还具有很大的提升空间.本文梳理现有的DR业务,基于现有的时空编码(space time coding,STC)编码技术原理,提出了一种改进型...     

基于压缩感知的低复杂度分数时延信道估计方法

基于压缩感知(compressed sensing,CS)技术的信道估计方法已被应用于正交频分复用(orthogonal frequency division multiplexing,OFDM)系统的信道估计中以提高频谱利用率。然而,传统的时域普通采样方法会导致信道测量矩阵不够精细,无法精确恢复信道状态信息。针对这一问题,提出利用分数时延信道模型模拟系统的无线多径信道,利用接收端时域过采样方法细化信道测量矩阵以提高信道估计精度。同时,为了克服由时域过采样导致的算法复杂度增加的问题,提出一种改进正交匹配追踪算法(modified orthogonal matching pursuit,MOMP)。仿真实验结果表明,在分数时延信道条件下,提出的接收端时域过采样方法能准确检测到信道的分数时延且提出的MOMP算法能显著降低估计算法的计算复杂度。     

基于二次分解与IGWO-LSSVR模型的超短期风速预测研究

针对风速序列的非线性导致预测精度不高的问题,提出了一种基于二次分解技术和改进灰狼算法的风速预测模型.首先,利用该模型对风速序列进行完备经验模态分解(CEEMD),并且对复杂度过大的前3个分量采用变分模态分解(VMD)进行二次分解;然后,对分解后的各个分量采用改进灰狼算法(IGWO)优化最小二乘支持向量回归(LSSVR)...     

SSOR preconditioned GPBiCG method for the linear interference cancellation of asynchronous CDMA systems

The decorrelator or the linear minimum mean-squared-error (LMMSE) detector has its computational complexity of O(K ³) where K is the number of users. On the other hand, the computational complexity of iterative detector algorithms such as conjugate gradient (CG) and generalized product bi-conjugate gradient (GPBiCG) methods only require the computational complexity O(K ²) per iteration. In this paper, the symmetric successive overrelaxation (SSOR) preconditioning scheme is applied to the GPBiCG method. The performance of the detectors is investigated and it is found that the SSOR preconditioned GPBiCG method can provide significantly faster convergence.     

Improved Tomlinson-Harashima precoding for the downlink of multi-user MIMO systems

By pre-equalizing the interlayer interference at the transmitter, the Tomlinson-Harashima precoding (THP) algorithm provides a solution for the downlink of multi-user multiple-input multiple-output (MIMO) systems, in which, because of the absence of cooperation among mobiles, receiver-based layer-separation algorithms cannot be implemented. In this paper, a new THP algorithm using the minimum mean-square error (MMSE) criterion is developed for the downlink of multi-user MIMO systems. This algorithm, called the MMSE THP algorithm, provides significant performance improvement compared to the zero-forcing (ZF) THP algorithm discussed in the literature. Moreover, ordering of the rows of the channel matrix is found to be important to the THP system performance, and the way in which this ordering affects the system structure is presented. An ordering lemma that generalizes the conditions, under which the ?best-first? ordering is optimal, is introduced.With this lemma it is proved that the ?best-first? ordering method achieves the optimal order in the minimax noise-variance sense for the ZF THP and the optimal order in the minimax error-variance sense for the MMSE THP. Simulation results show the performance advantage attained by the MMSE THP and the optimal ordering.     

正交频分复用前置编码技术在宽带电力线通信中的应用

基于正交频分复用(OFDM)的概念,提出在宽带电力线通信(PLC)中应用前置编码改进常用编码OFDM的新技术;在分析常用编码OFDM技术应用于宽带电力线通信时存在的缺点的基础上,给出了具体的前置编码方案;还在实际低压电力载波通道模型上对这两种技术进行了宽带电力线通信模拟仿真实验,仿真结果表明,应用前置编码OFDM技术可显著减小传输信号的误码率,并可简化基于常用编码OFDM技术的通信系统实现的复杂性.     

On the design of Chebyshev endfire arrays subject to a performance index

A numerical method for the optimization of Chebyshev endfire antenna arrays, under a nonlinear constraint, is presented. Starting from a set of initial parameters (number of elements, equidistance, side lobe level, half-power beamwidth) we proceed to the design procedure subject to a desired value of a performance index. The method is based on the least squares technique where the constraint is applied through a Lagrangian multiplier. The resulting Chebyshev-like pattern fulfills the constraint whereas it loses the initial characteristic of equal side lobes. The presented method is applied for radiation efficiency and quality factor indices and gives remarkable results for different Chebyshev arrays.     

Research on Low Sampling Rate Digital Pre-distortion Technology Based on Improved Chebyshev Polynomial

This paper presents a low sampling rate digital pre-distortion technique based on an improved Chebyshev polynomial for the non-linear distortion problem of amplifiers in 5G broadband communication systems. An improved Chebyshev polynomial is used to construct the behavioural model of the broadband amplifier, and an undersampling technique is used to sample the output signal of the amplifier, reduce the sampling rate, and extract the pre-distortion parameters from the sampled signal through an indirect learning structure to finally correct the non-linearity of the amplifier system. This technique is able to improve the linearity and efficiency of the power amplifier and provides better flexibility. Experimental results show that by constructing the behav-ioural model of the amplifier using memory polynomials (MP), generalised polynomials (GMP) and modified Chebyshev polynomials respectively, the adjacent channel power ratio of the obtained system can be improved by more than 13.87dB, 17.6dB and 19.98dB respectively compared to the output signal of the amplifier without digital pre-distortion. The Chebyshev polynomial improves the neighbourhood channel power ratio by 6.11dB and 2.38dB compared to the memory polynomial and generalised polynomial respectively, while the normalised mean square error is effectively improved and enhanced. This shows that the improved Chebyshev pre-distortion can guarantee the performance of the system and improve the non-linearity better.     

A new preconditioned conjugate gradient power flow

A new solution methodology for the constant matrix, decoupled power flow problem is presented in this paper. The proposed method uses the conjugate gradient method instead of the traditional direct solution of Ax=b for updating the power flow variables. The conjugate gradient method is accelerated with an approximate inverse matrix preconditioner obtained from a linear combination of matrix-valued Chebyshev polynomials. The new method has been tested on several systems of different sizes. In terms of speed, the method is comparable to the fast decoupled load flow in serial environments but it is more amenable to parallel and vector processing since it contains only matrix-vector multiplications.     

基于级联STATCOM的CPS-SPWM脉冲相移技术

载波移相SPWM(CPS-SPWM)技术作为级联H桥静止无功补偿器(STATCOM)最常用的调制方法,对级联H桥STATCOM输出电压精度、实时性等性能有着重要的影响。通过分析对比CPS-SPWM技术的三种脉冲生成方法—自然采样法、对称规则采样法以及不对称规则采样法,提出基于不对称规则采样的CPS-SPWM脉冲相移技术,以解决传统CPS-SPWM技术在级联H桥数较多时DSP控制复杂、FPGA硬件资源不足等问题。与传统CPS-SPWM技术的仿真对比表明,当级联H桥数目较多时,所设计方法能够在保证STATCOM输出特性的基础上,有效减少硬件资源,简化了电路设计,更便于工程应用。     

A novel rate-2 full diversity algebraic space-time code

Orthogonal space-time block codes (OSTBCs) have attracted considerable attention due to their low complexity linear decoding and full diversity in Rayleigh fading channels. However, OSTBCs exist only for certain numbers of transmit antennas and do not provide full code rate when more than two transmit antennas are used. In this paper, a novel rate-2 algebraic space-time code that combines coordinate-interleaving and group precoding is proposed. By properly choosing the designed parameters, the coding scheme can achieve full diversity order and high coding gain. The receiver adopts polynomial complexity sphere decoding algorithm to get maximum likelihood (ML) performance. Analysis and simulations illustrate that the new code exhibits significant performance gain over the conventional OSTBCs and diagonal algebraic space-time code.