Blind equalization in spatial multiplexing MIMO-OFDM systems based on vector CMA and decorrelation criteria

In this paper we address the problem of blind recovery of multiple OFDM data streams in a Multiple-Input Multiple-Output (MIMO) system. We propose an equalization algorithm which is based on a combined criterion designed to cancel both inter-symbol interference (ISI) and co-channel interference (CCI). ISI is minimized by using a modified Vector Constant Modulus criterion while CCI is minimized by a decorrelation criterion. We establish conditions for the existence of the stable minima corresponding to the zero forcing receiver which performs the joint blind equalization and the co-channel signal cancellation. The local convergence properties of the algorithm are proved under the assumption that the balance parameter weighting the two criteria is set appropriately. We also provide the optimal value for this parameter. Reliable performance is achieved with relatively fast convergence and small steady-state error. The implementation of the blind equalizer requires low-computational cost, without any matrix inversions or other expensive operations.     

平坦瑞利衰落信道中虚拟MIMO信号盲识别

文中首先讨论了无线通信中的单用户单天线信号、虚拟MIMO信号和MIMO信号三种信号的模型，然后讨论了非混合信号情况下，通过用MUSIC算法对这三种信号的DOA进行盲估计，盲识别出平坦瑞利衰落信道中虚拟MIMO信号的方法。仿真结果表明，该方法是可行的．     

跳频信号时-频域分析与参数盲估计方法

本文提出一种基于SPW时频分析来估计未知跳频信号参数的方法。该方法能够有效描绘跳频图案,具有分辨率高、运算量小、抗噪声能力强等优点。文中详细讨论了SPW时频分析方法,给出了参数盲估计算法的具体步骤及在低信噪比下的算法完善,并进行了仿真试验和性能分析。     

Binary constant modulus blind equalization for multi-level QAM signals under Gaussian and non-Gaussian noise

A binary constant modulus algorithm (BCMA) is proposed in this work for the blind equalization of multi-level quadrature amplitude modulation (QAM) systems. A novel cost function and its corresponding iteration formula are developed, which removes both the excess error and the steady state error introduced in the design of the most popular constant modulus algorithm (CMA). Theoretical analysis indicates the proposed algorithm can solve the performance degradation of CMA applying to the non-constant QAM signals. Moreover, it can combat the impulsiveness of alpha stable noise. Simulation results illustrate the effectiveness and robustness of the new algorithm under both Gaussian and non-Gaussian environments.     

基于点扩散函数支持域扩展的多帧未匹配退化图像盲解卷积复原

多帧盲解卷积算法利用多帧退化图像进行复原可以获得清晰原始图像和点扩散函数的信息,受到了很多研究者的关注。目前大部分多帧盲解卷积算法都需要对多帧退化图像进行匹配预处理,以消除图像间平移引入的算法求解误差。本文利用频率内的多帧盲解卷积算法对未匹配的退化图像进行处理,不需要进行预匹配处理,只需要对点扩散函数的支持域进行扩展就可以复原获取清晰化的图像。利用傅里叶变换的性质对该方法的可行性进行了说明。同时对该方法进行了数字仿真实验,复原结果中的点扩散函数发生了相对移动消除了图像间未匹配的影响,证实了本文方法的有效性。     

基于Dual-Mode MCMA+DD双模式盲均衡算法研究*

为了兼顾误差性能和收敛速度,研究了将双模修正常量模算法和判决引导算法有机结合的双模式盲均衡算法.该算法在收敛初期采用双模修正常量模算法调整均衡器,然后根据判决条件自动切换到判决引导算法,最终实现信道的盲均衡.仿真结果表明：此算法收敛速度快、稳态误差小,并能在去除码间干扰的同时纠正信道固有的相位旋转,具有很好的实用性.     

Electrochemical investigations for copper electrodeposition of through-silicon via

This study uses electrochemical techniques with a rotating disk electrode (RDE) to investigate the effects of Cu²⁺ concentration and additives on electrodeposition of through-silicon vias (TSV). The plating bath with both PEG and SPS has an obvious suppression effect on Cu-RDE with a thin boundary layer from −350 to −634 mV (vs. Hg/Hg₂SO₄) and a wide potential range for the via-filling operation. The impedance and potentiodynamic scans show the adsorption of small molecule SPS is more stable than PEG, and the effect of PEG or SPS depends on the thickness of boundary layer obviously only in Tafel region. This study obtained high filling powers in both deep and shallow vias using the plating bath of 50 g/L Cu²⁺, and TSV filling in wafer-segment scale, with 20 μm via diameter and 100 μm via depth, verifies the performance predicted by the electrochemical techniques.     

Blind symbol rate estimation of satellite communication signal by Haar wavelet transform

As the raised cosine shaping filter is often employed in practical satellite communication system,the envelope fluctuation at the symbol transition point is decreased which leads to the failure of the common wavelet algorithm under low SNR.Accordingly,a method of blind symbol rate estimation using signal preprocessing and Haar wavelet is proposed in this paper.Firstly,the effect of filter shaping can be reduced by the signal preprocessing.Then,the optimal scale factor is searched and the signal is processed and analyzed by the Haar wavelet transform.Finally,the symbol rate line is extracted and a nonlinear filter method is inducted for improving the estimation performance.Theoretical analysis and computer simulation show the efficiency of the proposed algorithm under low SNR and small roll-off factor.     

Postprocessing and sparse blind source separation of positive and partially overlapped data

We study sparse blind source separation (BSS) for a class of positive and partially overlapped signals. The signals are only allowed to have nonoverlapping at certain locations, while they could overlap with each other elsewhere. For nonnegative data, a novel approach has been proposed by Naanaa and Nuzillard (NN) assuming that nonoverlapping exists for each source signal at some location of acquisition variable. However, the NN method introduces errors (spurious peaks) in the output when their nonoverlapping condition is not satisfied. To resolve this problem and improve robustness of separation, postprocessing techniques are developed in two aspects. One is to detect coherent and uncertain components from NN outputs by using multiple mixture data, then removing the uncertain portion to enhance signals. The other is to find better estimation of mixing matrix by leveraging reliable source peak structures in NN output. Numerical results on examples including NMR spectra of a ¹³C-1-acetylated carbohydrate with overlapping proton spin multiplets show satisfactory performance of the postprocessed sparse BSS and offer promise to resolve complex spectra without using multidimensional NMR methods.     

Performance analysis and simulation of various burst time plan generation methods in broadband satellite multimedia system

The Burst Time Plan (BTP) generation is the key for resource allocation in Broadband Satellite Multimedia (BSM) system. The main purpose of this paper is to minimize the system response time to users’ request caused by BTP generation as well as maintain the Quality of Service (QoS) and improve the channel utilization efficiency. Traditionally the BTP is generated periodically in order to simplify the implementation of the resource allocation algorithm. Based on the analysis we find that Periodical BTP Generation (P-BTPG) method cannot guarantee the delay performance, channel utilization efficiency and QoS simultaneously, especially when the capacity requests arrived randomly. The Optimized BTP Generation (O-BTPG) method is given based on the optimal scheduling period and scheduling latency without considering the signaling overhead. Finally, a novel Asynchronous BTP Generation (A-BTPG) method is proposed which is invoked according to users’ requests. A BSM system application scenario is simulated. Simulation results show that A-BTPG is a trade-off between the performance and signaling overhead which can improve the system performance insensitive to the traffic pattern. This method can be used in the ATM onboard switching satellite system and further more can be expended to Digital Video Broadcasting-Return Channel Satellite (DVB-RCS) system or IP onboard routing BSM system in the future.