Blind adaptive constrained constant modulus algorithms based on unscented Kalman filter for beamforming

This work proposes constrained constant modulus unscented Kalman filter(CCM-UKF) algorithm and its low-complexity version called reduced-rank constrained constant modulus unscented Kalman filter(RR-CCM-UKF) algorithm for blind adaptive beamforming. In the generalized sidelobe canceller(GSC) structure, the proposed algorithms are devised according to the CCM criterion. Firstly, the cost function of the constrained optimization problem is transformed to suit the Kalman filter-style state space model. Then, the optimum weight vector of the beamformer can be estimated by using the recursive formulas of UKF. In addition, the a priori parameters of UKF(system and measurement noises) are processed adaptively in the implementation. Simulation results demonstrate that the proposed algorithms outperform the existing methods in terms of convergence speeds, output signal-tointerference-plus-noise ratios(SINRs), mean-square deviations(MSDs) and robustness against steering mismatch.

WIDELY LINEAR RLS CONSTANT MODULUS ALGORITHM FOR COMPLEX-VALUED NONCIRCULAR SIGNALS

Based on the constant modulus criterion, a new Widely Linear(WL) blind equalizer and a novel widely linear recursive least square constant modulus algorithm are proposed to improve the blind equalization performance for complex-valued noncircular signals. The new algorithm takes advantage of the WL filtering theory by taking full use of second-order statistical information of the complex-valued noncircular signals. Therefore, the weight vector contains the complete second-order information of the real and imaginary parts to decrease the residual inter-symbol interference effectively. Theoretical analysis and simulation results show that the proposed scheme can significantly improve the equalization performance for complex-valued noncircular signals compared with traditional blind equalization algorithms.

BLIND EQUALIZATION OF MIMO SYSTEMS BASED ON ORTHOGONAL CONSTANT MODULUS ALGORITHM

This paper investigates adaptive blind source separation and equalization for Multiple Input Multiple Output (MIMO) systems. To effectively recover input signals, remove Inter-Symbol Interference (ISI) and suppress Inter-User Interference (IUI), the array input is first transformed into the signal subspace, then with the derived orthogonality between weight vectors of different input signals, a new orthogonal Constant Modulus Algorithm (CMA) is proposed. Computer simulation results illustrate the promising performance of the proposed method. Without channel identification, the proposed method can recover all the system inputs simultaneously and can be adaptive to channel changes without prior knowledge about signals.

Constant modulus semi-blind space-time equalizer based on structure risk minimum criterion

A new adaptive filtering principle based on capability control and semi-blind method is presented. A new semi-blind space-time equalizer based on constant modulus characteristic and structure risk minimum （SRM） criterion is also proposed. The equalizer sufficiently exploits the learning information of communication signals by using the structure information of filter itself through capability control technique. Namely, it maximizes the amount of learning information to im- prove filter tracking performance. Simulations are carried out and the result is compared with that of typical recursive least squares space-time equalizer （RLS-STE） and constant modulus semi-blind space-time equalizer （ CM-SB-STE ）. The results show that, even if with insufficient training data, the SRM constant modulus semi-blind space-time equalizer （SCM-SB-STE） keeps good tracking per- formance, showing promises in mobile wireless communications.

A Decorrelation Constant Modulus Algorithm for Multitarget Separation Using Adaptive Arrays

In this paper, an adaptive digital filter algorithm is presented to optimize the signal-to-noise ratio of an antenna array with multiuser signal inputs. These synchronous communication signals have constant envelope property and are transmitted through a Multiple-Input/Multiple-Output （MIMO） linear channel. This Multiuser Constant Modulus Algorithm （MU-CMA） using an antenna array can compensate for both Interuser Interference （IUI） and Intersymbol Interference （ISI）. The method is derived by minimizing the cost function of the constant modulus signals as well as cross-correlations between them. The simulation result in this paper shows the performance of this algorithm.

Widely linear UKF constant modulus algorithm for blind adaptive beamforming

Based on a uniform linear array, a new widely linear unscented Kalman filter-based constant modulus algorithm (WL-UKF-CMA) for blind adaptive beamforming is proposed. The new algorithm is designed according to the constant modulus criterion and takes full advantage of the noncircular property of the signal of interest (SOI), significantly increasing the output signal-to interference-plus-noise ratio (SINR), enhancing the convergence speed and decreasing the steady-state misadjustment. Since it requires no known training data, the proposed algorithm saves a large amount of the available spectrum. Theoretical analysis and simulation results are presented to demonstrate its superiority over the conventional linear least mean square-based CMA (L-LMS-CMA), the conventional linear recursive least square-based CMA (L-RLS-CMA), WL-LMS-CMA, WL-RLS-CMA and L-UKF-CMA.

New multitarget constant modulus array for CDMA systems

A new mulfitarget constant modulus array is proposed for CDMA systems based on least squares constant modulus algorithm. The new algorithm is called pre-despreading decision directed least squares constant modulus algorithm （D-DDLSCMA）. In the new algorithm, the pre-despreading is first applied for multitarget arrays to remove some multiple access signals, then the despreaded signal is processed by the algorithm which united the constant modulus algorithm and decision directed method. Simulation results illustrate the good performance for the proposed algorithm.

中国内地对台湾地区出口的影响因素分析——基于CMS模型

本文选取联合国贸易2002-2022年中国内地对台湾地区水产品出口贸易数据,运用CMS模型对中国内地水产品出口到台湾地区的影响因素进行两个层次的分析。结果表明:1.2002-2022年期间,中国内地对台湾地区水产品的出口呈现“缓增-激增-跌落”三个阶段,对台主要出口甲壳软体制品、鲜冷甲壳及软体类、生鲜冷冻鱼和鱼制品四类水产品。2.在2002-2022年期间的三个阶段中,竞争力效应和第二层次分解的综合竞争力效应是影响中国内地对台湾地区水产品出口的主导因素。3.在2018-2022年阶段台湾地区水产品进口规模扩大,但是中国内地水产品在台湾地区市场上的市场份额却降低。再此基础上,提出促进两岸水产品贸易相应的对策建议。

A novel constant modulus array for multiuser detection

This paper proposes a new multitarget constant modulus array structure for code division multiple access (CDMA) systems. The new algorithm for the structure is called pre-despreading and wavelet denoising constant modulus algorithm (D-WD-CMA). In the new algorithm, the pre-despreading is applied to multitarget arrays to remove some multiple access inter- ferences. After that the received signal is subjected to wavelet de-noising to reduce some noise, and used in CMA adaptive iteration for signal separation. Simulation results showed that the proposed algorithm performed better than the traditional CMA algorithm.

ADAPTIVE STEP-SIZE CONSTANT MODULUS ALGORITHM FOR BLIND MULTIUSER DETECTION IN DS-CDMA SYSTEMS

Blind Adaptive Step-size Constant Modulus Algorithm (AS-CMA) for multiuser detection in DS-CDMA systems is presented. It combines the CMA and the concept of variable step-size, uses a second LMS algorithm for the step size. It adjusts the step-size according to the minimum output-energy principle within a specified range, thus overcomes the problems of bad effect of fixed step-size LMS algorithm. Compared with Adaptive Step-size LMS (AS-LMS) algoritilrn, through simulations, this algorithm can adapt the changes of the environment, suppress multiple access interference in the dynamic environment and the stability of Signal to Interference Ratio (SIR) is superior to that of AS-LMS.

Robust adaptive beamforming for constant modulus signal of interest

It is required in the diagonally loaded robust adaptive beamforming the automatic determination of the loading level which is practically a challenging problem.A constant modulus restoral method is herein presented to choose the diagonal loading level adaptively for the extraction of a desired signal with constant modulus(a common feature of the phase modulation signals).By introducing the temporal smoothing technique,the proposed constant modulus restoral diagonally loaded robust adaptive beamformer provides increased capability compared with some existing robust adaptive beamformers in rejecting interferences and noise while protecting the signal-of-interest.Simulation results are included to illustrate the performance of the proposed beamformer.

密度和灌溉定额对76 cm等行距棉田土壤硝态氮分布和氮素利用的影响

【目的】研究76 cm等行距机采棉种植模式下,土壤硝态氮分布和氮素利用对密度和灌溉定额调控的响应机制,为优化76 cm等行距机采棉栽培模式提供理论依据。【方法】在大田试验基础上,设置3个种植密度(低密度M_(1),13.5×10^(4)株/hm^(2);中密度M 2,18×10^(4)株/hm^(2);高密度M_(3),22.5×10^(4)株/hm^(2))和灌溉定额[重度亏缺W_(1)(50%ET_(C)),3150 m^(3)/hm^(2);轻度亏缺W_(2)(75%ET_(C)),4050 m^(3)/hm^(2);充分灌溉W 3(100%ET_(C)),4980 m^(3)/hm^(2)]。研究其对76 cm等行距机采棉田土壤无机氮含量、土壤硝态氮分布及氮素利用的影响。【结果】在相同灌溉定额下,密度对土壤铵态氮含量、硝态氮分布的均匀性均有显著影响(P<0.05),随密度的升高,土壤铵态氮含量降低,上层土壤硝态氮占比呈先升高后降低,而硝态氮分布的均匀性则完全相反。在相同密度处理下,随灌溉定额的增加,土壤硝态氮含量、分布的均匀性、上层土壤硝态氮占比、表聚性显著降低。密度和灌溉定额及两因素交互对棉田氮生产效率、氮素偏生产力均有显著性影响(P<0.05),随密度的升高,氮生产效率呈先降低后升高趋势,氮素偏生产力则逐渐降低;随灌溉定额的增加,氮生产效率逐渐降低,氮素偏生产力则相反。以低度与重度亏缺灌溉处理氮素生产效率最高,而氮素偏生产力则以低密度、中密度与充分灌溉处理组合最高,但与高密度与重度亏缺灌溉处理组合没有显著差异。【结论】氮素偏生产力以低密度、中密度与充分灌溉处理组合最高,分别为13.56、13.54 kg/kg,与高密度与重度亏缺灌溉处理组合没有显著差异。

基于CMA算法的双模式盲均衡算法

常数模算法（ＣＭＡ）的收敛速度非常缓慢。为了加快收敛过程，一旦误码率降低到足够低，该算法必须切换到ＤＤ算法。为了克服这些缺点，本文利用ＱＡＭ信号分布在几个已知半径的圆上的特点，提出了两类多模盲均衡算法。在此基础上又提出一种双模式均衡方案：多模算法模式和常数模算法模式。研究表明，两类多模算法及双模式均衡方案收敛快。

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.

基于LCCMA的盲自适应多用户检测新算法

基于LCCMA(线性约束恒模算法)提出了一种新的盲自适应多用户检测算法。本文中提出的这种算法适用于多径衰落信道,能很好抵消多址干扰和克服多径衰落。仿真证明,这种算法的性能和基于子空间分解的多用户检测算法的性能相当,但运算复杂度低于子空间算法。因此这种算法的总体性能优于基于子空间分解的多用户检测算法,是值得进一步研究的课题,并使之推广应用。

MCA-CMA次分量分析恒模算法

提出了一种次分量分析恒模算法(Minor component analysis-constant modulus algorithm,MCA-CMA)。该算法从恒模代价函数出发,推导出一个基于Rayleigh熵形式的代价函数,根据Rayleigh熵的性质,可得出最优权矢量就是协方差矩阵的最小特征值所对应的特征矢量,从而引入次分量分析(MCA)寻找最优权矢量,因此该恒模算法称为MCA-CMA算法。仿真结果充分验证该算法的有效性。

改进CMA盲均衡算法的研究与分析

目前，常数模算法（constant modulus algorithm，CMA）应用非常广泛，但它存在收敛速度慢，剩余误差大的缺点。为加快收敛速度，一旦误码率降低到足够低，算法必须切换到DD（decision-directed）算法，针对其存在的缺点，提出了一种改进的CMA算法，通过理论分析得出：该算法具有收敛速度快、剩余误差小的特点。通过利用Matlab对改进前、后2种算法的仿真，对算法的有效性进行了验证。

中国羊绒及其制品贸易格局波动影响因素分析——基于CMS模型实证研究

我国是羊绒生产、加工、消费第一大国和羊绒产品贸易大国。根据UNComtrade相关数据,采用修正CMS模型分析我国原绒进口、无毛绒进出口和羊绒制品出口波动成因。研究发现,竞争效应是推动我国原绒进口增长主要因素,产品效应次之,增长效应作用最小;增长效应是我国无毛绒进出口贸易增长主要因素,竞争效应逐渐增强出口增长作用,产品效应对无毛绒进口增长贡献率较小且呈下降趋势,而对其抑制作用显著;增长效应是我国羊绒制品出口贸易增长主要因素,竞争效应贡献率较高且不断增加,而产品效应影响则越来越小。

异步CDMA系统中的LCDCM多用户检测器

将线性约束差分恒模算法(LCDCM)应用于异步CDMA系统的多用户检测.该检测器只要求了解目标用户的信息,运算较简单,且由于采用了自适应方法,检测器无需估计信号的幅度.分析及仿真结果表明,LCDCM检测器有很好的收敛速度和干扰抑制度,其性能优于传统检测器,且对用户数目的变化有很好的适应性.

一种新的CMA盲多用户检测算法

该文提出了一种新的盲自适应多用户检测算法,这种算法的计算复杂度为O(NL),其中N为扩频因子,L为取样数据窗长度。仿真分析表明,该文提出的算法稳态性能好,收敛速度特别快,且能适应环境的变化,是一种较好的多用户检测算法。