Instituto de Telecomunicações

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Publications

iSensA - A System for Collecting and Integrating Sensor Data

Publication . Caldeira, João; Soares, Vasco N. G. J.; Gaspar, Pedro Dinis; Rodrigues, Joel P. C.; Fontes, Ricardo; Silva, José Luís Lopes

The idea of monitoring several types of parameters in various environments has been motivating significant research works in Internet of Things (IoT). This paper presents the design and construction of iSensA, a system for integrating and collecting information from sensors. The solution implements a multi-sensor monitoring system and then expands the monitoring concept to an IoT solution, by employing multi-network access, Web services, database and web and mobile applications for user interaction. iSensA system is highly configurable, enabling several monitoring solutions with different types of sensors. Experiments have been performed on real application scenarios to validate and evaluate our proposition.

2018Journal article

Open access

A Reminiscence of ”Mastermind”: Iris/Periocular Biometrics by ”In-Set” CNN Iterative Analysis

Publication . Proença, H.; Neves, João C.

Convolutional neural networks (CNNs) have emerged as the most popular classification models in biometrics research. Under the discriminative paradigm of pattern recognition, CNNs are used typically in one of two ways: 1) verification mode (”are samples from the same person?”), where pairs of images are provided to the network to distinguish between genuine and impostor instances; and 2) identification mode (”whom is this sample from?”), where appropriate feature representations that map images to identities are found. This paper postulates a novel mode for using CNNs in biometric identification, by learning models that answer to the question ”is the query’s identity among this set?”. The insight is a reminiscence of the classical Mastermind game: by iteratively analysing the network responses when multiple random samples of k gallery elements are compared to the query, we obtain weakly correlated matching scores that - altogether - provide solid cues to infer the most likely identity. In this setting, identification is regarded as a variable selection and regularization problem, with sparse linear regression techniques being used to infer the matching probability with respect to each gallery identity. As main strength, this strategy is highly robust to outlier matching scores, which are known to be a primary error source in biometric recognition. Our experiments were carried out in full versions of two well known irises near-infrared (CASIA-IrisV4-Thousand) and periocular visible wavelength (UBIRIS.v2) datasets, and confirm that recognition performance can be solidly boosted-up by the proposed algorithm, when compared to the traditional working modes of CNNs in biometrics.

2019Journal article

Open access

Economic trade-off in the optimization of carrier aggregation with enhanced multi-band scheduling in LTE-Advanced scenarios

Publication . Robalo, Daniel; Velez, Fernando

This work proposes Long Term Evolution-Advanced (LTE-A) integrated Common Radio Resource Management (iCRRM) for inter-band carrier aggregation (CA) between band 7 (2.6 GHz) and band 20 (800 MHz), considering bandwidths of 5 and 20 MHz. The iCRRM entity performs component carrier (CC) scheduling and increases user’s quality of service and experience while considering mobile video traffic. The performance from a new enhanced multi-band scheduling (EMBS) algorithm is compared to the one from a basic multi-band scheduler (BMBS), an integer programming-based general multi-band scheduling (GMBS) and the case without CA. EMBS involves reduced optimization scheduling complexity and allows the allocation of UEs to one or both CCs simultaneously, whereas both BMBS and GMBS only support one CC per UE. Simulations results have shown that, for 5 MHz CCs and cell radius equal to 1,000 m, with EMBS and GMBS, the 3GPP and ITU-T’s 1% packet loss ratio (PLR) threshold is only exceeded above 58 UEs (goodputs of 7.48 and 7.40 Mbps, respectively), while with BMBS only 54 UEs (6.9 Mbps) are supported. Without CA, the minimum obtained PLR is approximately 2%. For CCs with bandwidth of 20 MHz, only EMBS has been considered. The PLR threshold is not exceeded up to 40 users and the value of QoE raises from 2.86 (for 5-MHz bandwidth) to 3.96, while a gain of 9.56 occurs in supported goodput, increasing from 7.48 to 71.53 Mbps. Results from the cost/revenue trade-off have shown substantial improvements by using CA. Although the profit increases as the price per megabyte increases, it is verified that prices can be much lower if a bandwidth of 20 MHz is available. Assuming values for the supported goodput under the PLR ≤1% range and 20 MHz CCs, it has been shown that the percentage of profit decreases at a considerably higher rate (compared to 5-MHz bandwidth), due to the lower rate of decrease from the curve for costs. Considering PLR ≤1%, the profit curve for 20 MHz CCs at 0.001 € /MByte is similar to the one for 5 MHz CCs and price of 0.01 € /MByte for the smallest cell sizes (few hundreds of meters) but starts to decrease faster for larger cells.

2015-03Journal article

Open access

Radio Resource Management of Heterogeneous Small Cell Networks

Publication . Paulo, Rui Filipe Rosa; Velez, Fernando José da Silva

While mobile communication users demand new high speed services with enhanced quality, there will always be a need to optimize cellular networks. This work explores the behavior of indoor and outdoor small cells while reducing the cell size to increase system capacity in both links. After justifying evolution of the use of small cells, the concepts of ultra-dense networks and heterogeneous networks toward 5G are then presented. In the initial part of this work, we have chosen a 3GPP 5x5 grid geometry for indoor scenarios. The average signal-to-interference-plus-noise ratio (SINR) has been studied for reuse pattern two and two types of deployment topologies, one with 25 HeNBs and another with 4 HeNBs. We have also addressed the exponential effective SINR mapping (EESM) by extending the study for topologies with 5 and 6 HeNBs. Based on an improved version of LTE-Sim, network performance has been evaluated in terms of the goodput, packet loss ratio (PLR), delay, and the maximum number of supported users. We have evaluated the performance by considering 4, 5, 6 and 25 HeNBs. Results complied with the 3GPP recommendations for PLR and delay. One observed that system capacity is higher for topologies with 25 HeNBs, followed by topologies with 6 HeNBs and 4 HeNBS, and then the indoor deployments with 5 HeNBs. Different packet schedulers have been considered. Results have shown that, with the considered applications and schedulers, it is possible to reduce the transmitter power of HeNBs without compromising the small cell network performance. In the final part of the work an urban micro line-of-sight cell scenario has been studied by comparing the 2.6 GHz, 3.5 GHz, and 5.62 GHz frequency bands while considering the ITU-R M.2135-1 dual slope path loss model (DS-PLM) in the system level simulations. Results have been obtained for different values of the cell radius. System capacity has been determined by considering the 3GPP quality target of 2% for video applications. For all schedulers and frequency bands, for cell radius shorter than the breakpoint distance, the PLR increases when the cell radius decreases. [...]

2022-10-26Doctoral thesis

Open access

Wireless Sensor Networking Applied to Swarms of Aquatic Drones

Publication . Nadziejko, Aleksandra Katarzyna; Velez, Fernando José da Silva

Aquatic Unmanned Surface Vehicles (USV) have potential in a variety of maritime activities such as environmental monitoring or sea-life tracking. They can be applied to military missions sup¬porting army in potentially dangerous situations such as reconnaissance or surveillance. USV are capable of many tasks due to technological progress and minimization of equipment in recent years. Size and price drop while reliability improved enables development of large scale multi-agent systems consisting of autonomous USVs. Multi-agent system of aquatic autonomous USVs may act like a distributed sensing system im¬proving the overall performance when compared to the performance of one unit of USV: more units in the system, larger monitored area. A promising approach inspired from nature is swarm intelligence, which can be found for instance in population of insects such as ants. Swarmbe¬haviour is a motion of large number of units, where each one is autonomous but only as a group they are able to solve the problem. The exchange of information between units is essential for the success of the group. Wireless Sensor Networks (WSNs) have potential as communication architecture applied to swarms. A scenario for the communication both with and within the swarm has been proposed. The challenges implied by tough environmental conditions call for heterogeneous approach such as the one proposed in this dissertation. A communication within the swarm is held using short-range communication technology such as XBee-PRO modules. All nodes acting as sensing agents are equipped with short-range communication technology. The communication with the swarm is held using nodes acting as gateways to the shore equipped with long-range technology, such as SX1272 modules from Semtech, called LoRa. The deployment of nodes acting as gateways to the shore, called buoys, with fixed localization has been proposed. Each node in the network is aware of the GPS coordinates of buoys, thus in case of communication loss, it can orient itself in the direction of the nearest buoy, increasing chances of successful communication with the base station. The short-range communication XBee-PRO technology has been tested in order to determine communication range with and without Line of Sight (LoS). The objective is to improve the range of the communication link, which nowadays in held via Wi-Fi in the distance around 30 m. The results were promising for real-world implementation into swarms of aquatic surface drones.

2016-7-4Master thesis

Open access