共查询到18条相似文献,搜索用时 578 毫秒
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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。 相似文献
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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。 相似文献
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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。 相似文献
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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. 相似文献
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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。 相似文献
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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)... 相似文献
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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. 相似文献
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《Electrical and Computer Engineering, Canadian Journal of》2007,32(3):133-144
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. 相似文献
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Dimitrios G. Babas John N. Sahalos 《Electrical Engineering (Archiv fur Elektrotechnik)》2007,90(2):155-160
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. 相似文献
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Research on Low Sampling Rate Digital Pre-distortion Technology Based on Improved
Chebyshev Polynomial
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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. 相似文献
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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. 相似文献
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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。 相似文献
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Xiufeng Jin Guangguo Bi 《Frontiers of Electrical and Electronic Engineering in China》2009,4(4):371-377
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. 相似文献