人工智能在移动通信网络中的应用:基于机器学习理论的信道估计与信号检测算法

机器学习是人工智能的重要方向之一,文章介绍两种机器学习理论应用于移动通信网络的案例。首先介绍一种基于期望最大化算法的信道估计器,不需要导频也可实现对信道的盲估计,提高了系统的吞吐率。随后介绍了一种基于深度神经网络的信道估计和信号恢复算法,该算法能够隐性地分析信道的特性,直接将信号恢复出来,当导频数据减少时其性能优于传统算法。神经网络估计器虽然训练模型复杂,但后续可直接将信号恢复,降低了信号处理的复杂度。     

基于随机复杂度约束的高维特征自动选择算法

高维特征选择问题是机器学习研究领域的公开问题,当前流行的1-范数约束正则化解决方案存在的主要问题是缺乏特征组选能力和特征选择能力受样本容量限制.本文从随机复杂度理论的模型冗余度最优下界推导得出了一种易于求解的基于零-范数约束的特征选择算法模型.该算法不仅可证优化,而且具备自动特征选择能力,克服了1-范数约束方法的主要缺...     

基于SVM及其改进算法的fMRI图像分类性能研究

为了提出一种更适用于分析fMRI图像特征的机器学习算法,引入机器学习近年提出的、具有较好的泛化能力、并能够保证极值解是全局最优解的新方法支持向量机（SVM）算法,具体选择了PSVM、SSVM、LPSVM、NSVM 4种SVM改进算法以及基本SVM算法应用于fMRI图像的分类问题,在MATLAB平台上进行了算法仿真实现。在对各种算法的分类计算时间、分类精确度两个方面进行比较和讨论后,得到PSVM算法在fMRI图像的分类问题上,有较好的综合性能。     

面向通信感知计算一体化网络业务的用户体验质量估计

未来的6G网络有望成为集感知、通信和计算为一体的通感算一体化网络，以满足各种新型业务的极致化需求。用户体验质量将成为网络运维管理的关注重点。因此，提出并设计了一种新的QoE估计方法。首先，应用机器学习算法构建KPI与QoE关联性分析模型。其次，根据关联性分析结果搭建深度神经网络利用KPI实现QoE估计。最后，仿真结果表明所提方法在估计用户体验质量方面具有很高的准确性。     

基于OBE的机器学习课程教学设计

阐述通过机器学习课程的学习，学生能够掌握机器学习的基本理论和基本方法，形成机器学习程序设计思维习惯，强化Python程序设计能力的教学目标，以及基于机器学习的7个经典算法为主要课程的教学内容。     

一种基于支撑矢量机的多用户检测算法

与现有的机器学习算法相比,在样本有限的情况下,支撑矢量机具有更强的分类推广能力.本文将支撑矢量机与多用户检测相结合,提出了一种新型的多用户检测算法.理论推导和仿真结果表明该算法的有效性.     

用于车牌字符识别的SVM算法

支持向量机(SVM)是20世纪90年代初由Vapnik等人提出的一类新型机器学习方法，此方法能够在训练样本很少的情况下达到很好的分类推广能力。本文应用SVM算法时车牌中的汉字字符进行识别，无字符特征提取提高了识别速度，并且可得到较高的识别率。实验讨论了SVM算法用于字符识别时，不同的核函数时识别率的影响。实验结果表明，用SVM算法进行车牌字符识别具有较高的识别率。     

一种基于机器学习的卫星干扰信号DOA估计算法

随着现代通信技术的发展,波达方向(Direction of Arrival,DOA)估计在卫星通信抗干扰中越来越重要,通过对干扰信号的DOA实时和精确估计,为后续抗干扰提供依据。传统的估计算法计算任务重且耗费时间,不利于对干扰信号进行实时定位,如MUSIC,ESPRIT算法等。在此背景下,提出了基于机器学习的DOA估计方法,采用神经网络学习方位特征样本,在空间信号和方位角之间建立非线性映射关系,利用训练后的网络估计方位角度,可减小运算量和提高估计精度。在分析了机器学习算法特点的基础上,提出基于BP神经网络和RBF神经网络的DOA估计算法,并从算法复杂度、信噪比、相干性和信号类型等方面评价了估计性能,通过仿真结果分析,得出RBF网络DOA估计性能优于BP网络的结论。     

基于约束恒模准则的盲自适应多址干扰抑制算法

为克服基于恒模的盲自适应多址干扰抑制算法中，由于估计幅值选择不合适而造成算法不收敛的缺点，本文提出了几种自适应方法来跟踪目标用户的幅度，从而保证了算法的全局收敛，并提高了干扰抑制能力。计算机仿真结果证明了该方法的有效性与可行性。     

基于直接判决和导频跟踪的OFDM系统快时变信道估计

提出了一种基于直接判决的OFDM系统的快时变信道估计方法。采用了直接判决算法进行信道估计，并从中选择有效的估计结果，联合导频信号进行信道跟踪。将基于训练序列的信道估计结果作为直接判决算法的初始值，利用传输信号直接判决的统计特性进行了信道估计，并利用改进的导频算法进一步地跟踪信道在时间上的变化。Simulink仿真结果表明，该估计算法适用于时变信道，比基于导频的信道估计方法和基于训练序列的信道估计方法效果都要好。     

深度学习算法及其在光学的应用

深度学习作为机器学习的重要分支，自出现之初就掀起了机器学习的又一次高潮。深度学习在诸如图像识别与分类、语义分割、智能驾驶等多个领域有着优异的表现。同时，深度学习算法以其抽象特征识别和提取特性，极强的模型构建和泛化推广能力，被广泛应用于光学领域，如计算全息图产生与成像、数字全息的无参数重建和光谱共振曲线预测等方面。详细介绍了深度学习的基本原理及在图像分类、超分辨成像、计算全息和数字全息、表面等离激元共振曲线预测、超表面的结构设计等方面的典型应用研究，并探讨了深度学习在物理光学领域未来值得研究的方向。     

WCI 04 On the Application of Ensembles of Classifiers to the Diagnosis of Pathologies of the Vertebral Column: A Comparative Analysis

This paper reports results from a comprehensive performance comparison among standalone machine learning algorithms (SVM, MLP and GRNN) and their combinations in ensembles of classifiers when applied to a medical diagnosis problem in the field of Orthopedics. All the aforementioned learning strategies, which currently comprises the classification module of the SINPATCO platform, are evaluated according to their ability in discriminating patients as belonging to one out of three categories: Normal, Disk Hernia and Spondylolisthesis. Confusion matrices of all learning algorithms are also reported, as well as a study of the effect of diversity in the design of the ensembles. The obtained results clearly indicate that the ensembles of classifiers have better generalization performance than standalone classifiers     

Regularized manifold information extreme learning machine

By exploiting the thought of manifold learning and its theoretical method, a regularized manifold information ex-treme learning machine algorithm aimed to depict and fully utilize manifold information was proposed. The proposed algo-rithm exploited the geometry and discrimination manifold information of data to perform network of ELM. The proposed algorithm could overcome the problem of the overlap of information. Singular problems of inter-class and within-class were solved effectively by using maximum margin criterion. The problem of inadequate learning with limited samples was solved. In order to demonstrate the effectiveness, comparative experiments with ELM and the related update algorithms RAFELM, GELM were conducted using the commonly used image data. Experimental results show that the proposed algorithm can significantly improve the generalization performance of ELM and outperforms the related update algorithms.     

数据集类别不平衡性对迁移学习的影响分析

数据集类别不平衡性是机器学习领域的常见问题,对迁移学习也不例外。本文针对迁移学习下数据集类别不平衡性的影响研究不足的问题,重点研究了以下几种不平衡性处理方法对迁移学习的影响效果分析:过采样、欠采样、加权随机采样、加权交叉熵损失函数、Focal Loss函数和基于元学习的L2RW（Learning to Reweight）算法。其中,前三种方法通过随机采样消除数据集的不平衡性,加权交叉熵损失函数和Focal Loss函数通过调整传统分类算法的损失函数以适应不平衡数据集的训练,L2RW算法则采用元学习机制动态调整样本权重以实现更好的泛化能力。大量实验结果表明,在上述各种不平衡性处理方法中,过采样处理和加权随机采样处理更适合迁移学习。      

Can threshold networks be trained directly?

Neural networks with threshold activation functions are highly desirable because of the ease of hardware implementation. However, the popular gradient-based learning algorithms cannot be directly used to train these networks as the threshold functions are nondifferentiable. Methods available in the literature mainly focus on approximating the threshold activation functions by using sigmoid functions. In this paper, we show theoretically that the recently developed extreme learning machine (ELM) algorithm can be used to train the neural networks with threshold functions directly instead of approximating them with sigmoid functions. Experimental results based on real-world benchmark regression problems demonstrate that the generalization performance obtained by ELM is better than other algorithms used in threshold networks. Also, the ELM method does not need control variables (manually tuned parameters) and is much faster.     

Evolutionary Extreme Learning Machine and Its Application to Image Analysis

Extreme learning machine (ELM) and evolutionary ELM (E-ELM) were proposed as a new class of learning algorithm for single-hidden layer feedforward neural network (SLFN). In order to achieve good generalization performance, E-ELM calculates the error on a subset of testing data for parameter optimization. Since E-ELMemploys extra data for validation to avoid the overfitting problem, more samples are needed for model training. In this paper, the cross-validation strategy is proposed to be embedded into the training phase so as to solve the overtraining problem. Based on this new learning structure, two extensions of E-ELM are introduced. Experimental results demonstrate that the proposed algorithms are efficient for image analysis.     

一种基于支持向量机的分类算法

支持向量机是在统计学理论基础上提出的一种新的机器学习方法，由于其出色的学习性能，该技术已成为机器学习界的研究热点，并成功地应用在文本分类、图像识别、生物信息处理等领域。这里简要介绍了支持向量机算法及其应用，并且讨论了其未来的发展方向。     

Pareto-Based Multiobjective Machine Learning: An Overview and Case Studies

Machine learning is inherently a multiobjective task. Traditionally, however, either only one of the objectives is adopted as the cost function or multiple objectives are aggregated to a scalar cost function. This can be mainly attributed to the fact that most conventional learning algorithms can only deal with a scalar cost function. Over the last decade, efforts on solving machine learning problems using the Pareto-based multiobjective optimization methodology have gained increasing impetus, particularly due to the great success of multiobjective optimization using evolutionary algorithms and other population-based stochastic search methods. It has been shown that Pareto-based multiobjective learning approaches are more powerful compared to learning algorithms with a scalar cost function in addressing various topics of machine learning, such as clustering, feature selection, improvement of generalization ability, knowledge extraction, and ensemble generation. One common benefit of the different multiobjective learning approaches is that a deeper insight into the learning problem can be gained by analyzing the Pareto front composed of multiple Pareto-optimal solutions. This paper provides an overview of the existing research on multiobjective machine learning, focusing on supervised learning. In addition, a number of case studies are provided to illustrate the major benefits of the Pareto-based approach to machine learning, e.g., how to identify interpretable models and models that can generalize on unseen data from the obtained Pareto-optimal solutions. Three approaches to Pareto-based multiobjective ensemble generation are compared and discussed in detail. Finally, potentially interesting topics in multiobjective machine learning are suggested.     

基于机器学习的可见光通信信号处理研究现状

随着无线通信领域的发展,具有诸多优点的可见光通信(VLC)已经发展成为了一种具有广阔前景的通信手段。然而,可见光通信中的各种非线性效应会给其信号处理带来诸多的困难,并恶化系统的性能。机器学习在解决非线性问题方面具有很大的优势和潜力,结合机器学习算法的可见光通信技术必然具有巨大的研究价值。已有研究表明,传统的机器学习算法如K-means、DBSCAN以及支持向量机(SVM)等在预均衡、后均衡、抗系统抖动,以及相位纠正等方面均有很好的表现。而深度神经网络(DNN)则因为其强大的非线性拟合能力能够更进一步提升VLC系统的性能。对以上几种方法进行了分析和介绍,并对其在可见光通信信号处理领域的应用进行了分析与总结,希望可以为机器学习解决可见光通信方面的各种非线性问题提供参考。