65 research outputs found
Feature Selection for MAUC-Oriented Classification Systems
Feature selection is an important pre-processing step for many pattern
classification tasks. Traditionally, feature selection methods are designed to
obtain a feature subset that can lead to high classification accuracy. However,
classification accuracy has recently been shown to be an inappropriate
performance metric of classification systems in many cases. Instead, the Area
Under the receiver operating characteristic Curve (AUC) and its multi-class
extension, MAUC, have been proved to be better alternatives. Hence, the target
of classification system design is gradually shifting from seeking a system
with the maximum classification accuracy to obtaining a system with the maximum
AUC/MAUC. Previous investigations have shown that traditional feature selection
methods need to be modified to cope with this new objective. These methods most
often are restricted to binary classification problems only. In this study, a
filter feature selection method, namely MAUC Decomposition based Feature
Selection (MDFS), is proposed for multi-class classification problems. To the
best of our knowledge, MDFS is the first method specifically designed to select
features for building classification systems with maximum MAUC. Extensive
empirical results demonstrate the advantage of MDFS over several compared
feature selection methods.Comment: A journal length pape
Application of advanced machine learning techniques to early network traffic classification
The fast-paced evolution of the Internet is drawing a complex context which
imposes demanding requirements to assure end-to-end Quality of Service. The
development of advanced intelligent approaches in networking is envisioning
features that include autonomous resource allocation, fast reaction against
unexpected network events and so on. Internet Network Traffic Classification
constitutes a crucial source of information for Network Management, being decisive
in assisting the emerging network control paradigms. Monitoring traffic flowing
through network devices support tasks such as: network orchestration, traffic
prioritization, network arbitration and cyberthreats detection, amongst others.
The traditional traffic classifiers became obsolete owing to the rapid Internet
evolution. Port-based classifiers suffer from significant accuracy losses due to port
masking, meanwhile Deep Packet Inspection approaches have severe user-privacy
limitations. The advent of Machine Learning has propelled the application of
advanced algorithms in diverse research areas, and some learning approaches have
proved as an interesting alternative to the classic traffic classification approaches.
Addressing Network Traffic Classification from a Machine Learning perspective
implies numerous challenges demanding research efforts to achieve feasible
classifiers. In this dissertation, we endeavor to formulate and solve important
research questions in Machine-Learning-based Network Traffic Classification. As a
result of numerous experiments, the knowledge provided in this research constitutes
an engaging case of study in which network traffic data from two different
environments are successfully collected, processed and modeled.
Firstly, we approached the Feature Extraction and Selection processes providing our
own contributions. A Feature Extractor was designed to create Machine-Learning
ready datasets from real traffic data, and a Feature Selection Filter based on fast
correlation is proposed and tested in several classification datasets. Then, the
original Network Traffic Classification datasets are reduced using our Selection
Filter to provide efficient classification models. Many classification models based on
CART Decision Trees were analyzed exhibiting excellent outcomes in identifying
various Internet applications. The experiments presented in this research comprise
a comparison amongst ensemble learning schemes, an exploratory study on Class
Imbalance and solutions; and an analysis of IP-header predictors for early traffic
classification. This thesis is presented in the form of compendium of JCR-indexed
scientific manuscripts and, furthermore, one conference paper is included.
In the present work we study a wide number of learning approaches employing the
most advance methodology in Machine Learning. As a result, we identify the
strengths and weaknesses of these algorithms, providing our own solutions to
overcome the observed limitations. Shortly, this thesis proves that Machine
Learning offers interesting advanced techniques that open prominent prospects in
Internet Network Traffic Classification.Departamento de TeorĂa de la Señal y Comunicaciones e IngenierĂa TelemáticaDoctorado en TecnologĂas de la InformaciĂłn y las Telecomunicacione
Adaptive tracking of people and vehicles using mobile platforms
Tracking algorithms have important applications in detection of humans and vehicles for border security and other areas. For large-scale deployment of such algorithms, it is critical to provide methods for their cost- and energy-efficient realization. To this end, commodity mobile devices have significant potential for use as prototyping and testing platforms due to their low cost, widespread availability, and integration of advanced communications, sensing, and processing features. Prototypes developed on mobile platforms can be tested, fine-tuned, and demonstrated in the field and then provide reference implementations for application-specific disposable sensor node implementations that are targeted for deployment. In this paper, we develop a novel, adaptive tracking system that is optimized for energy-efficient, real-time operation on off-the-shelf mobile platforms. Our tracking system applies principles of dynamic data-driven application systems (DDDAS) to periodically monitor system operating characteristics and apply these measurements to dynamically adapt the specific classifier configurations that the system employs. Our resulting adaptive approach enables powerful optimization of trade-offs among energy consumption, real-time performance, and tracking accuracy based on time-varying changes in operational characteristics. Through experiments employing an Android-based tablet platform, we demonstrate the efficiency of our proposed tracking system design for multimode detection of human and vehicle targets.publishedVersionPeer reviewe
Sustainable Transparency in Recommender Systems: Bayesian Ranking of Images for Explainability
Recommender Systems have become crucial in the modern world, commonly guiding
users towards relevant content or products, and having a large influence over
the decisions of users and citizens. However, ensuring transparency and user
trust in these systems remains a challenge; personalized explanations have
emerged as a solution, offering justifications for recommendations. Among the
existing approaches for generating personalized explanations, using visual
content created by the users is one particularly promising option, showing a
potential to maximize transparency and user trust. Existing models for
explaining recommendations in this context face limitations: sustainability has
been a critical concern, as they often require substantial computational
resources, leading to significant carbon emissions comparable to the
Recommender Systems where they would be integrated. Moreover, most models
employ surrogate learning goals that do not align with the objective of ranking
the most effective personalized explanations for a given recommendation,
leading to a suboptimal learning process and larger model sizes. To address
these limitations, we present BRIE, a novel model designed to tackle the
existing challenges by adopting a more adequate learning goal based on Bayesian
Pairwise Ranking, enabling it to achieve consistently superior performance than
state-of-the-art models in six real-world datasets, while exhibiting remarkable
efficiency, emitting up to 75% less CO during training and inference with
a model up to 64 times smaller than previous approaches
Coupling different methods for overcoming the class imbalance problem
Many classification problems must deal with imbalanced datasets where one class \u2013 the majority class \u2013 outnumbers the other classes. Standard classification methods do not provide accurate predictions in this setting since classification is generally biased towards the majority class. The minority classes are oftentimes the ones of interest (e.g., when they are associated with pathological conditions in patients), so methods for handling imbalanced datasets are critical.
Using several different datasets, this paper evaluates the performance of state-of-the-art classification methods for handling the imbalance problem in both binary and multi-class datasets. Different strategies are considered, including the one-class and dimension reduction approaches, as well as their fusions. Moreover, some ensembles of classifiers are tested, in addition to stand-alone classifiers, to assess the effectiveness of ensembles in the presence of imbalance. Finally, a novel ensemble of ensembles is designed specifically to tackle the problem of class imbalance: the proposed ensemble does not need to be tuned separately for each dataset and outperforms all the other tested approaches.
To validate our classifiers we resort to the KEEL-dataset repository, whose data partitions (training/test) are publicly available and have already been used in the open literature: as a consequence, it is possible to report a fair comparison among different approaches in the literature.
Our best approach (MATLAB code and datasets not easily accessible elsewhere) will be available at https://www.dei.unipd.it/node/2357
Ensemble diversity for class imbalance learning
This thesis studies the diversity issue of classification ensembles for class imbalance learning problems. Class imbalance learning refers to learning from imbalanced data sets, in which some classes of examples (minority) are highly under-represented comparing to other classes (majority). The very skewed class distribution degrades the learning ability of many traditional machine learning methods, especially in the recognition of examples from the minority classes, which are often deemed to be more important and interesting. Although quite a few ensemble learning approaches have been proposed to handle the problem, no in-depth research exists to explain why and when they can be helpful. Our objectives are to understand how ensemble diversity affects the classification performance for a class imbalance problem according to single-class and overall performance measures, and to make best use of diversity to improve the performance.
As the first stage, we study the relationship between ensemble diversity and generalization performance for class imbalance problems. We investigate mathematical links between single-class performance and ensemble diversity. It is found that how the single-class measures change along with diversity falls into six different situations. These findings are then verified in class imbalance scenarios through empirical studies. The impact of diversity on overall performance is also investigated empirically. Strong correlations between diversity and the performance measures are found. Diversity shows a positive impact on the recognition of the minority class and benefits the overall performance of ensembles in class imbalance learning. Our results help to understand if and why ensemble diversity can help to deal with class imbalance problems.
Encouraged by the positive role of diversity in class imbalance learning, we then focus on a specific ensemble learning technique, the negative correlation learning (NCL) algorithm, which considers diversity explicitly when creating ensembles and has achieved great empirical success. We propose a new learning algorithm based on the idea of NCL, named AdaBoost.NC, for classification problems. An ``ambiguity" term decomposed from the 0-1 error function is introduced into the training framework of AdaBoost. It demonstrates superiority in both effectiveness and efficiency. Its good generalization performance is explained by theoretical and empirical evidences. It can be viewed as the first NCL algorithm specializing in classification problems.
Most existing ensemble methods for class imbalance problems suffer from the problems of overfitting and over-generalization. To improve this situation, we address the class imbalance issue by making use of ensemble diversity. We investigate the generalization ability of NCL algorithms, including AdaBoost.NC, to tackle two-class imbalance problems. We find that NCL methods integrated with random oversampling are effective in recognizing minority class examples without losing the overall performance, especially the AdaBoost.NC tree ensemble. This is achieved by providing smoother and less overfitting classification boundaries for the minority class. The results here show the usefulness of diversity and open up a novel way to deal with class imbalance problems.
Since the two-class imbalance is not the only scenario in real-world applications, multi-class imbalance problems deserve equal attention. To understand what problems multi-class can cause and how it affects the classification performance, we study the multi-class difficulty by analyzing the multi-minority and multi-majority cases respectively. Both lead to a significant performance reduction. The multi-majority case appears to be more harmful. The results reveal possible issues that a class imbalance learning technique could have when dealing with multi-class tasks. Following this part of analysis and the promising results of AdaBoost.NC on two-class imbalance problems, we apply AdaBoost.NC to a set of multi-class imbalance domains with the aim of solving them effectively and directly. Our method shows good generalization in minority classes and balances the performance across different classes well without using any class decomposition schemes.
Finally, we conclude this thesis with how the study has contributed to class imbalance learning and ensemble learning, and propose several possible directions for future research that may improve and extend this work
IP102: A large-scale benchmark dataset for insect pest recognition
Insect pests are one of the main factors affecting agricultural product yield. Accurate recognition of insect pests
facilitates timely preventive measures to avoid economic losses. However, the existing datasets for the visual classification task mainly focus on common objects, e.g., flowers and dogs. This limits the application of powerful deep
learning technology on specific domains like the agricultural field. In this paper, we collect a large-scale dataset
named IP102 for insect pest recognition. Specifically, it contains more than 75,000 images belonging to 102 categories, which exhibit a natural long-tailed distribution. In addition, we annotate about 19, 000 images with bounding boxes for object detection. The IP102 has a hierarchical taxonomy and the insect pests which mainly affect one specific agricultural product are grouped into the same upper level category. Furthermore, we perform several baseline experiments on the IP102 dataset, including handcrafted and deep feature based classification methods.
Experimental results show that this dataset has the challenges of interand intra- class variance and data imbalance. We believe our IP102 will facilitate future research on practical insect pest control, fine-grained visual classification, and imbalanced learning fields. We make the dataset and pre-trained models publicly available at https://github.com/
xpwu95/IP10
Accelerating Audio Data Analysis with In-Network Computing
Digital transformation will experience massive connections and massive data handling. This will imply a growing demand for computing in communication networks due to network softwarization. Moreover, digital transformation will host very sensitive verticals, requiring high end-to-end reliability and low latency. Accordingly, the emerging concept “in-network computing” has been arising. This means integrating the network communications with computing and also performing computations on the transport path of the network. This can be used to deliver actionable information directly to end users instead of raw data.
However, this change of paradigm to in-network computing raises disruptive challenges to the current communication networks. In-network computing (i) expects the network to host general-purpose softwarized network functions and (ii) encourages the packet payload to be modified. Yet, today’s networks are designed to focus on packet forwarding functions, and packet payloads should not be touched in the forwarding path, under the current end-to-end transport mechanisms. This dissertation presents fullstack in-network computing solutions, jointly designed from network and computing perspectives to accelerate data analysis applications, specifically for acoustic data analysis.
In the computing domain, two design paradigms of computational logic, namely progressive computing and traffic filtering, are proposed in this dissertation for data reconstruction and feature extraction tasks. Two widely used practical use cases, Blind Source Separation (BSS) and anomaly detection, are selected to demonstrate the design of computing modules for data reconstruction and feature extraction tasks in the in-network computing scheme, respectively. Following these two design paradigms of progressive computing and traffic filtering, this dissertation designs two computing modules: progressive ICA (pICA) and You only hear once (Yoho) for BSS and anomaly detection, respectively. These lightweight computing modules can cooperatively perform computational tasks along the forwarding path. In this way, computational virtual functions can be introduced into the network, addressing the first challenge mentioned above, namely that the network should be able to host general-purpose softwarized network functions. In this dissertation, quantitative simulations have shown that the computing time of pICA and Yoho in in-network computing scenarios is significantly reduced, since pICA and Yoho are performed, simultaneously with the data forwarding. At the same time, pICA guarantees the same computing accuracy, and Yoho’s computing accuracy is improved.
Furthermore, this dissertation proposes a stateful transport module in the network domain to support in-network computing under the end-to-end transport architecture. The stateful transport module extends the IP packet header, so that network packets carry message-related metadata (message-based packaging). Additionally, the forwarding layer of the network device is optimized to be able to process the packet payload based on the computational state (state-based transport component). The second challenge posed by in-network computing has been tackled by supporting the modification of packet payloads.
The two computational modules mentioned above and the stateful transport module form the designed in-network computing solutions. By merging pICA and Yoho with the stateful transport module, respectively, two emulation systems, i.e., in-network pICA and in-network Yoho, have been implemented in the Communication Networks Emulator (ComNetsEmu). Through quantitative emulations, the experimental results showed that in-network pICA accelerates the overall service time of BSS by up to 32.18%. On the other hand, using in-network Yoho accelerates the overall service time of anomaly detection by a maximum of 30.51%. These are promising results for the design and actual realization of future communication networks
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