ISEL - Eng. Elect. Tel. Comp. - Comunicações
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- Cross-device platform for collaborative and immersive experiences in mixed realityPublication . Lucas, Letícia; Costa, Carla; Jorge, Pedro MendesThis work aims to develop a platform for managing Augmented Reality (AR) and Virtual Reality (VR) devices, enabling multiple users to engage in collaborative and immersive experiences occurring both in the physical and digital world. The proposed solution addresses challenges in synchronization, data transmission, and real-time rendering, so that the multiple participants - either co-located or geographically dispersed - can share a unified, high-fidelity experience. This research intends to advance mixed reality technologies for education, entertainment, and business purposes. To demonstrate this cross-device approach, an application using the MagicLeap2 and MetaQuest3 devices is implemented. This application allows various users to collaboratively interact within the same mixed reality environment. Unity3D is the core framework of this system, and OpenXR is the layer that ensures hardware compatibility.
- Cross-device platform for collaborative and immersive experiences in mixed realityPublication . Lucas, Letícia; Costa, Carla; Jorge, Pedro MendesThis work aims to develop a platform for managing Augmented Reality (AR) and Virtual Reality (VR) devices, enabling multiple users to engage in collaborative and immersive experiences occurring both in the physical and digital world. The proposed solution addresses challenges in synchronization, data transmission, and real-time rendering, so that the multiple participants - either co-located or geographically dispersed - can share a unified, high-fidelity experience. This research intends to advance mixed reality technologies for education, entertainment, and business purposes. To demonstrate this cross-device approach, an application using the MagicLeap2 and MetaQuest3 devices is implemented. This application allows various users to collaboratively interact within the same mixed reality environment. Unity3D is the core framework of this system, and OpenXR is the layer that ensures hardware compatibility.
- Millimeter-wave testbed and modeling in NeXt generation URLLC communicationsPublication . Dias, Eurico; Garcia Raposo, Duarte Miguel; Esfahanizadeh, Homa; Cohen, Alejandro; Vasudevan, Vipindev Adat; Ferreira, Tania; Luís, Miguel; Sargento, Susana; Médard, MurielModeling realistic millimeter-wave (mmWave) channels is crucial to the study of ultra-reliable communication in next-generation wireless networks. MmWave provides significant gains over sub-6GHz communication but has very stringent requirements on channel conditions, since slight variations in the channel may result in significant performance degradation of mmWave communication. In this work, we present an experimental mmWave testbed and the mathematical modeling of the channels using the measurements collected from an outdoor testbed that complies with IEEE 802.11ad. We show how the model fits the reality and demonstrate the impact of adaptive causal network coding in mmWave real and simulated networks.
- Design of a Cardiopulmonary antenna for vital signs monitoring robust to different subjectsPublication . Cardoso, João; Pinho, Pedro; Gouveia, Carolina; Albuquerque, DanielWith the advancement of wireless diagnosis and treatment technologies, antennas deployed close to the human body are now widely used. The use of on-body antennas, along with other technologies, presents itself as an innovative method for detecting and monitoring vital signs. These antennas can be attached directly on the body or on clothes, making it comfortable to use and less invasive when compared to conventional methods, allowing at-home monitoring of elderly patients or high risk workers with a single antenna. In this paper, a robust high bandwidth patch antenna was developed to operate in the dedicated Industrial, Scientific and Medical frequency band, namely at 2.45 GHz, capable of monitoring vital signs in any subject. This work presents the design and results of a robust cardiopulmonary antenna, to be further used to monitor the respiratory rate of five different subjects, each one with different physiognomy.
- Real-time GPS indoor for USV tracking using lookup tablePublication . Vieira, Fábio; Teodoro, Pedro; Jorge, Pedro MendesThis study introduces an approach that utilizes Lookup Tables (LUT) to enable real-time tracking of an Unmanned Surface Vehicle (USV) in an indoor setting, using a fish-eye camera. The proposed method streamlines image processing and achieves O(1) complexity, significantly reducing application run time. The paper also outlines the process of calibrating the fish-eye camera to correct image distortion, computing the homography matrix for re-projection, and obtaining a virtual top view of the camera’s field of view. The paper provides a detailed explanation of the replacement of the undistortion and re-projection steps with the new LUT method. Experimental results demonstrate a significant enhancement in the process’s run time, making it feasible for real-time tracking, regardless of the image size.
- Efficient feature selection for intrusion detection systems with priority queue-based GRASPPublication . Quincozes, Vagner E.; Quincozes, Silvio E.; Albuquerque, Célio; Passos, Diego; Massé, DanielThe Greedy Randomized Adaptive Search Proce dure for Feature Selection (GRASP-FS) is a recently-proposed metaheuristic that optimizes the feature selection process for Intrusion Detection Systems (IDS) by combining exploration and refinement techniques for more assertive intrusion detection. However, GRASP-FS may be time and resource-consuming for large datasets. In this work, we propose GRASPQ-FS, an extended version of GRASP-FS using Priority Queues to reduce resource consumption and processing time. As an additional contribution, we provide a comprehensive analysis of the most suitable parameters for our RASPQ-FS. Our results reveal that GRASPQ-FS can speed up feature selection up to 90% over GRASP-FS, without compromising F1-Score. Also, we observed that a priority queue with 50 solutions saved 50% in execution time while increasing the F1-Score by 4.5%.
- Feature transformation and reduction for text classificationPublication . J. Ferreira, Artur; Figueiredo, MarioText classification is an important tool for many applications, in su pervised, semi-supervised, and unsupervised scenarios. In order to be processed by machine learning methods, a text (document) is usually represented as a bag-of-words (BoW). A BoW is a large vector of features (usually stored as floating point values), which represent the relative frequency of occurrence of a given word/term in each document. Typically, we have a large number of features, many of which may be non-informative for classification tasks and thus the need for feature transformation, reduction, and selection arises. In this paper, we propose two efficient algorithms for feature transformation and reduction for BoW-like representations. The proposed algorithms rely on simple statistical analysis of the input pattern, exploiting the BoW and its binary version. The algorithms are evaluated with support vector machine (SVM) and AdaBoost classifiers on standard benchmark datasets. The experimental results show the adequacy of the reduced/transformed binary features for text classification problems as well as the improvement on the test set error rate, using the proposed methods.
- Boosting of (very) weak learnersPublication . J. Ferreira, Artur; Figueiredo, MárioIn this paper we apply boosting to weak (binary) learners. The main idea is to combine the output of several simple learners in order to obtain a better classifier. As weak learners we consider generative classifiers and radial basis function classifiers.Our tests on synthetic data show that the proposed algorithm has good convergence properties. On benchmark data, boosting of these weak learners attains results close to the well-known Real AdaBoost algorithm (with decision trees) and support vector machines, constituting a low complexity competitive choice.
- Long distance real-time echo cancellationPublication . J. Ferreira, Artur; Marques, Paulo; Carvalho, HélderThis paper describes an implementation of a long distance echo canceller, operating on full-duplex with handsfree and in real-time with a single Digital Signal Processor (DSP). The proposed solution is based on short length adaptive filters centered on the positions of the most significant echoes, tracked by time delay estimators. To deal with double talking situations a speech detector is employed. The floating-point DSP TMS320C6713 from Texas Instruments is used with software written on the C++ programming language using some compiler optimizations to reduce execution time. The resulting algorithm enables long distance echo cancellation with low computational requirements. It reaches greater echo return, loss enhancement and shows faster convergence speed than the conventional solu tion. Our experimental results also approach the CCITT G.165 recommendation for echo cancellers.
- On the use of suffix arrays for memory-efficient Lempel-Ziv data compressionPublication . J. Ferreira, Artur; Oliveira, Arlindo L.; Figueiredo, MarioThe Lempel-Ziv 77 (LZ77) and LZ-Storer-Szymanski (LZSS) text compression algorithms use a sliding window over the sequence of symbols, with two sub-windows: the dictionary (symbols already encoded) and the look-ahead-buffer (LAB) (symbols not yet encoded). Binary search trees and suffix trees (ST) have been used to speedup the search of the LAB over the dictionary, at the expense of high memory usage [1]. A suffix array (SA) is a simpler, more compact data structure which uses (much) less memory [2,3] to hold the same information. The SA for a length m string is an array of integers ([1], ...[k], ...a[m]) that stores the lexicographic order of suffix k of the string; sub-string searching, as used in LZ77/LZSS, is done by searching the SA.