Percorrer por autor "Rodrigues, António"
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- Aspects of Cellular Planning for Emergency and Safety Services in Mobile WiMax NetworksPublication . Velez, Fernando J.; Carvalho, Vitor; Santos, Dany; Marcos, Rui P.; Costa, Rui; Sebastião, Pedro; Rodrigues, AntónioThis work addresses cellular planning aspects for a WiMax (worldwide interoperability for microwave access) point-to-multipoint wireless network to be developed in the region of Beira Interior. It is concentrated in more detail in the district of Covilha, and, particularly, in the urban area of the city, in order to guarantee communications from the Health Science Faculty of University of Beira Interior (HSF/UBI)/ Hospital Pero da Covilha to all central urban area of the city. By having aspects related with the carrier-to-noise and carrier-to-interference ratios into account, one concluded that it is necessary to consider a cellular structure with sectorisation, and cell coverage distances around 3 km. Because this zone is very hilly, the optimization of the choice of the location for base stations is essential; the potentialities of the GIS (geographic information systems) tools were explored to optimise the existence of line of sight coverage in coverage. Future research directions regarding architectures for interoperability and mobile IP, security, and the impact of multimedia applications are also addressed.
- Cellular Planning of an IEEE 802.16 Wireless Metropolitan Area NetworkPublication . Velez, Fernando José; Carvalho, Vitor; Santos, Dany; Marcos, Rui P.; Costa, Rui; Sebastião, Pedro; Tomé, Ricardo; Rodrigues, AntónioThis work intends to develop a WiMax (Worldwide Interoperability for Microwave Access) point-to-multipoint wireless network that includes all the district of Covilhã, and particularly the urban area of the city in detail, with the objective to guarantee a point-to-multipoint connection from the Health Science Faculty of the University of Beira Interior (HSF/UBI) / Hospital Pêro da Covilhã to all urban area of the centre of the city. The cellular planning of this WiMax mobile network was done having in account aspects related with the carrier-to-noise ratio and carrier-to-interference ratio, concluding that is necessary to consider a cellular structure with coverage distances of 3 km and sectorisation is needed to create a high capacity wireless network in the urban area of Covilhã. Because this zone is very hilly, the choice of the location for base stations is essential; one used the potentialities of the GIS (Geographic Information Systems) tools to optimize the line of sight coverage and, simultaneously, reduce the propagation exponent. A new mobile IP architecture for Wi-Fi/WiMax interoperability is being conceived, developed and implemented based in Media Independent Handover.
- Concepção e Planeamento de Redes sem Fios IEEE 802.16Publication . Carvalho, Vitor; Santos, Dany; Marcos, Rui; Costa, Rui; Velez, Fernando J.; Sebastião, Pedro; Rodrigues, António; Riscado, José; Romão, José; Cavaleiro, VictorEsta comunicação aborda aspectos de projecto e planeamento celular duma rede sem fios WiMax (IEEE 802.16) para interligar ponto-a-ponto a Faculdade de Ciências da Saúde da Universidade da Beira Interior (FCS/UBI) ao Hospital Amato Lusitana (Castelo Branco), uma rede ponto-multiponto para ligar a FCS/UBI/Hospital Pêro da Covilhã a toda a área urbana do centro da cidade da Covilhã e uma rede móvel celular dedicada aos serviços públicos de emergência e de segurança, abrangendo toda a região da Beira-Interior, fazendo-se a avaliação detalhada da existência de linha de vista no concelho da Covilhã. Efectuou-se o planeamento tendo em conta aspectos relacionados com a relação portadora-ruído, C/N, e a relação portadora-interferência, concluindo-se ser necessário usar sectorização e considerar sobreposição de micro-células à estrutura macro-celular (cell overlay). Utilizaram-se ferramentas GIS para auxiliar no processo de determinação das posições para as estações de base e da respectiva área com linha de vista, de forma a assegurar um expoente de propagação baixo. Dos resultados para a ligação ponto-a-ponto Covilhã-Gardunha-Castelo Branco, conclui-se que é possível assegurar comunicação com qualidade a 3.5 GHz, mas a 5.8 GHz, como a distância máxima para a qual C/N<(C/N)min é de 25 km, é necessário aumentar o ganho de pelo menos uma das antenas para assegurar a qualidade da ligação.
- Hybrid WiMAX and Wi-Fi networks for the support of b-Learning and TelemedicinePublication . Costa, Rui; Velez, Fernando José; Robalo, Daniel Luís Silveira; Marques, Marco; Comissário, Cláudio; Riscado, José; Cavaleiro, Victor; Sebastião, Pedro; Rodrigues, Antóniohis paper addresses the deployment of hybrid WiMAX and Wi-Fi networks for the support of always best connected telemedicine and health sciences education applications. The available services include a LMS (Learning Management System) and several structured functionalities for b-Learning. For the support of these services, fixed and wireless LANs have been deployed, as well as an experimental point-to-multipoint IEEE 802.16-2004 network covering part of the city of Covilhã. The FCS (Health Sciences Faculty) Campus as well as the tutorial rooms of the Faculty spread at the different Hospitals of the region of Beira Interior, Portugal, are benefiting from WLAN coverage, whose backhaul is supported by WiMAX point-to-point links with relays. Field trials results were compared with the ones arising from the WiMAX radio links design, and very similar results were achieved. Service quality was guaranteed by adjusting QoS parameters.
- Influence of a Few More Channels for Voice Support in B3G Multi-Service Traffic in the Presence of MobilityPublication . Paulo, Rui R.; Velez, Fernando J.; Rodrigues, AntónioThe analysis of the impact of voice-over-IP into HSPA and LTE multi-service traffic is a challenge. The validation of a Bernoulli-Poisson-Pascal multi-service traffic model in the presence of mobility is explored for different values for the number of channels. A mixture of voice (VOI) and video telephony (VTE) is considered. In a previous work, a critical situation was assumed where the total number of channels was exactly the same as needed by four VTE sessions. However, when few extra channels are added there is a significant reduction on VTE on/off blocking probability. With this few extra resources, VOI can now be easily supported. Since it is supported on top of a system saturated with VTE sessions, Pbonoff decreases 4.6 times for VTE. Since the number of resources is not critical anymore, the range of values of the offered traffic for which the theoretical model agrees with simulation results becomes wider. There is no significative difference between the multi-service traffic results for the seven cell geometry and the roundabout (or ring) cellular topologies in the presence of mobility.
- Planning and Deployment of WiMAX and Wi-Fi Networks for Health Sciences EducationPublication . Sebastião, Pedro; Velez, Fernando J.; Costa, Rui; Robalo, Daniel; Comissário, Cláudio; Rodrigues, AntónioOptimal planning for the integration of WiMAX (Worldwide Interoperability for Microwave Access) and Wi-Fi (Wireless Fidelity) technologies enables real technical conditions to make a hybrid Wi-Fi/WiMAX network available at the Health Sciences Faculty of University of Beira Interior, supporting nomadic applications like videoconference, voice over IP and communication of high resolution video/image. A simple wireless planning tool is designed and used in this optimal planning, which facilitates the design and implementation of Wi-Fi and WiMAX networks in indoor and outdoor environments. The tool gives useful information through quick coverage/capacity based procedures, as the output is the number and position of the APs (access points)/BSs (base stations) or an estimation of the total cost of implementation, based on data provided by different manufacturers. While planning methodologies are already stable for Wi-Fi, and propagation models have already been widely validated, the propagation models available for WiMAX still need to be tuned, which motivates the need to carry out propagation measurements. For IEEE 802.16-2004 networks operating at 3.5 GHz, by comparing the measurement results with the ones obtained using the modified Friis and the SUI (Stanford University Interim) models, it was concluded that, for a suburban area of Covilhã, Portugal, the use of the modified Friis model with a propagation exponent ~3 is more appropriate than the use of the SUI one, although for coverage distances between 275 and 475 m the SUI model (SUI-B and mainly SUI-C) may still be used. WiMAX cellular planning exercises are presented for the zone of Covilhã. Carrier-to-noise-plus-interference issues are discussed, and Geographic Information Systems are applied to determine the existence of line-of-sight in rural and sparse urban areas. One of the main conclusions arising from this work is the strong need of using sectorial antennas to guarantee an adequate coverage and interference mitigation for several terrain types and environments, including hilly terrain.
- Planning and Deployment of WiMAX NetworksPublication . Sebastião, Pedro; Velez, Fernando; Costa, Rui; Robalo, Daniel; Rodrigues, AntónioIncorporation of measurement based techniques in Worldwide Interoperability for Microwave Access (WiMAX) are required to improve IEEE 802.16 engineering methodologies. Wireless planning methodologies are presented, supported by a planning tool which facilitates the design and implementation of WiMAX networks. Propagation models available for WiMAX still need to be tuned and further validated. By comparing IEEE 802.16-2004 measurement results at 3.5GHz with computed values using the modified Friis and the Stanford University Interim (SUI) models, for a suburban area, we found that the use of the modified Friis equation with a propagation exponent ∼3 is more appropriate than the use of the SUI model, although, for coverage distances between 275 and 475 m, the SUI-B and mainly SUI-C models may still be used. From the analysis of the carrier-to-noise-plusinterference ratio, it is clear that both noise and interference present a strong limitation to the cellular reuse performance of fixedWiMAX mainly for higher order modulation and codingschemes.With a reuse pattern K = 7, cell throughputs near the maximum are only achieved in the uplink if sub-channelisation is used together with sectorization. The planning tool provides planners with practical and useful information through quick coverage/capacity based procedures, and outputs the number and position of the base stations and an estimation of the total cost of implementation, based on data provided by different equipment manufacturers. WiMAX cellular planning exercises are presented for the zone of Covilhã, Portugal, where Geographic Information Systems are used for representation of rural and sparse urban areas. One of the main conclusions is the strong need to use sector antennas in order to guarantee an adequate coverage, and higher system capacity whilst mitigating interference for several terrain types and environments, including hilly terrain.
- Planning of an IEEE 802.16e Network for Emergency and Safety ServicesPublication . Velez, Fernando José; Caravalho, Vitor; Santos, Dany; Marcos, Rui P.; Costa, Rui; Sebastião, Pedro; Rodrigues, AntónioAn overlaid Wimax cellular structure is proposed for emergency and safety services, with micro-cells covering urban hotspots over a macro-cellular structure. In the region of Beira Interior the process of cellular planning has to account for carrier-to-noise-interference ratio. Sectorisation is used in order to reduce reuse patterns and increase system capacity, while cell overlay is proposed to overcome coverage problems in large towns and cities. Geographic Information Systems tools are considered for Line-of-Sight discovery, and ~75% of LoS coverage is guaranteed in the city of Covilhã. The point-to-point component is also being incorporated in the planning tool. By comparing the 3.5GHz and the 5.8GHz bands one concludes that it is possible to use lower values of the antenna gains in the first case.
- Radio and Network PlanningPublication . Velez, Fernando J.; Sebastião, Pedro; Costa, Rui; Robalo, Daniel; Comissário, Cláudio; Rodrigues, António; Aghvami, A. HamidThis chapter starts by presenting the Stanford University Interim (SUI) and modified Friis propagation models. Although the SUI model is being recommended for WiMAX, the comparison between the model and experimental results show that, in our environment, at 3.5 GHz, the modified Friis model with gama = 3 fits better the measurement values. From the analyses of the signal-to-noise-plusinterference ratio, SNIR, interference-to-noise ratio and reuse pattern, it is found that both noise and interference present a strong limitation to the performance of fixed WiMAX, mainly for higher order modulation and coding schemes (MCSs). In general terms, the use of sectorization in fixed WiMAX enables to reduce the reuse pattern while considering sub-channelisation allows for improvement on the coverage. The reduction of the reuse pattern directly corresponds to an increase in the system capacity but the improvement in the coverage range (through subchannelisation) can also allow for an improvement in UL system capacity, as adaptive MCS are used. Two different approaches are considered for graphical cellular planning, and the district of Covilha˜ is considered as a case study. On the one hand, one considered a GIS based WiMAX planning tool conceived by considering coverage issues, frequency reuse, and the impact of the different classes of service. On the other, WinpropTM is used as it distinguishes among different MCS in the graphical presentation of the results. Both tools consider the information coming from the digital terrain profile. The GIS functionalities allow for appropriately adjusting azimuth and tilt of antennas. This cellular planning exercises confirm the results of theoretical analysis, where different crowns are achieved for the coverage with each MCS (corresponding to a given range of values for SNIR), for the maximum physical throughput, and for the “best server” cells. The frequency radio resources should be considered as the most valuable resourceduring the planning of wireless broadband access networks. As a rule, spectral efficiency needs to be optimized by using several advanced techniques, corresponding to an optimization from the cost-benefit point of view.
- Unified propagation model for Wi-Fi, UMTS and WiMAX planning in mixed scenariosPublication . Varela, Frederico; Sebastião, Pedro; Correia, Americo; Cercas, Francisco; Rodrigues, António; Velez, Fernando J.; Robalo, DanielThis paper presents an unified and empirical propagation model to obtain the received power in mixed scenarios, with outdoor and indoor environments, or in a scenario with only one kind of environment, either for an urban, sub-urban or rural scenario, with or without vegetation. This unified model is called the Lisbon University Institute (LUI) one and can be included into planning tools for wireless communication systems. The developed model is suitable for Path Loss prediction in mobile, as well as fixed wireless network systems, e.g., Wireless Fidelity, Universal Mobile Telecommunications System and Worldwide Interoperability for Microwave Access, considering Line-of-Sight or Non-Line-of-Sight propagation conditions.