Navegando por Assunto "Dispositivos de redes sem fio"

Agora exibindo 1 - 5 de 5

Acesso aberto (Open Access)
Extensão do plano de controle sem fio para ambientes experimentais outdoor
(Universidade Federal do Pará, 2017-12-14) NÚÑEZ, Alexsander; ABELÉM, Antônio Jorge Gomes; http://lattes.cnpq.br/5376253015721742
The use of experimental wireless environments is a powerful tool for validating surveys in Future Internet, testing products and services. USA, Europe, Japan, Brazil, among other countries, through initiatives such as FIRE, GENI, WISHFULL and FIBRE, already provide such environments for researchers. However, the topology of these environments, in the wireless and outdoor context, is still very limited due to the need for wired infrastructure to control the devices. In this way, this dissertation presents a wireless control plan proposal for these outdoor experimental environments, maintaining its characteristics of use and adding functionalities through the proposed control architecture based on the framework called Orchestrator for Wireless Experimental Networks of Multiple Jumps Defined by Software (OREx).
Acesso aberto (Open Access)
FPGA-based testbed for fronthaul signal compression: implementation and validation
(Universidade Federal do Pará, 2017-03-24) FORTUNA, Joary Paulo Wanzeller; KLAUTAU JÚNIOR, Aldebaro Barreto da Rocha; http://lattes.cnpq.br/1596629769697284
In recent years the world has seen an increasing demand for mobile services with high capacity and low cost. Such requirements forced the radio access technologies to be rethought. Among the different architectures proposed in literature, one that has got a lot of attention was the Centralized Radio Access Network (C-RAN). This strategy proposes to share the network resources through the centralization of the base-band processing and, as a result, reduce the network cost. Even though the centralization can bring several benefits, it also increases the distance between the point where the signal is captured and the point where it is processed. The link connecting both points is called fronthaul. In this scenario, the existing fronthaul technologies do not fit in the flexibility and cost requisites expected for the next generation mobile network, mainly due to the usage of dedicated optical links. One solution to these problems is the usage of Ethernet to transport fronthaul data, due to its ubiquitous presence, flexibility and low cost. In this work, a testbed for fronthaul based on Ethernet is presented, along with the implementation details and validation results. Also motivated by the Ethernet’s bandwidth limitation, this work presents the VHDL implementation of a compression technique for LTE signals, evaluated in real transport conditions with the testbed. The obtained results indicate that it is possible to utilize the Ethernet network infrastructure for fronthaul transport. Although, it is necessary to reduce the requirements of Fronthaul stream through, for example, the application of signal compression techniques and synchronization methods.
Acesso aberto (Open Access)
A Multi-tier fog architecture for video on demand streaming
(Universidade Federal do Pará, 2018-03-05) SANTOS, Hugo Leonardo Melo dos; CERQUEIRA, Eduardo Coelho; http://lattes.cnpq.br/1028151705135221
Users are changing their traditional communication paradigm based on voice calls or text messages to real-time or on demand video services consumed on mobile devices. In this sense, the transmission of video content considering an adequate Quality of Experience (QoE) in mobile wireless networking infrastructures is a critical issue in both academic and industrial communities. Furthermore, video on demand have a growing consumption over Internet requiring higher bandwidth and lower latency. In this context, a fog computing paradigm can enhance the user experience in wireless networks. Fog computing for video on demand streaming can improve QoE by both video caching and adaptation schemes. However, it is important to evaluate the performance of downloading the videos with diferent codec con_guration and cached closer to the user to measure the gain from the user perspective. We designed a multi-tier fog computing architecture with three levels located in the cloud, nearer the edge and in mobile devices. We evaluated the performance of downloading the video from multiple tier located in distinct geographical with a multimedia application. We assessed in an experimental environment with idle and congested network of streamed videos coded into H.264 and H.265 with three bitrates in a scenario deployed in the FIBRE testbed. We collected QoE metrics, playback start time, freeze times, QoS metric, round-time trip, and energy consumption to analyze the gains for each video configuration. These results showed an important understanding about cache, codec and bitrate schemes in multimedia networking scenarios.
Acesso aberto (Open Access)
Qualidade de vídeo baseada em perda de pacotes utilizando o padrão IEEE 802.11AC
(Universidade Federal do Pará, 2017-03-10) MATOS, Edemir Marcus Carvalho de; CASTRO, Bruno Souza Lyra; http://lattes.cnpq.br/1897829604434609; PELAES, Evaldo Gonçalves; http://lattes.cnpq.br/0255430734381362
The flow of digital multimedia information in wireless networks has grown exponentially due to the popularization of the IEEE 802.11 Standards as access technology, as well as the increase of devices (clients) that operate in this standard. High-resolution video streaming is also becoming commonplace in these networks, driving the development of more efficient CODECs. In this context, some QoE and QoS metrics must be met to deliver quality content to the end user. This dissertation studies the behavior of wireless video streaming using the IEEE 802.11ac standard operating in the 5.2 GHz range, the CODEC rated is the H.264 / AVC for the 720p, 1080p and 2160p resolutions. From the packet loss simulations during video transmission an estimate of the average loss of PSNR for each resolution was developed, finding the relation of the loss of video quality varying the resolution in function of the loss of packets. The proposed model presented good results when compared to the real data, obtaining RMSE of 2.32 dB and standard deviation of 2.2 dB. This modeling can aid in communication network planning as well as enhancement of new source encoders, resulting in a better quality of experience.
Acesso aberto (Open Access)
Sistema de aquisição de dados para monitoramento de malha de terra energizada
(Universidade Federal do Pará, 2015-11-18) SOUSA, Kleiber Tenório de; TOSTES, Maria Emilia de Lima; http://lattes.cnpq.br/4197618044519148; BEZERRA, Ubiratan Holanda; http://lattes.cnpq.br/6542769654042813
The good performance of grounding system in substations and generating plants is an essential condition for their operation according with established quality standards. Therefore a continuous monitoring system for grounding grid is an important tool to aid technical teams to identify failed zones that depreciate the Power Systems operation. Some traditional measuring methods in grounding grids need the power system shutdown. However the concession contracts allow penalties for the unavailability of generation and transmission facilities. Therefore the constant adoption of grounding grid evaluation without the plant shutdown is important. Having these specifications as target this Dissertation presents an embedded system development for voltage and current measurement. Another proposed system component is the software to manage the measuring network and organize the collected information in a database to produce grounding system operation reports. An important aspect of the system is the adoption of wireless network technology to data transfer between each measuring instrument and a web server installed in the power plant operation center. The experimentally obtained results reinforce the system contribution and encourage new developments.