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- Capacity Analysis in a Multi-service Mobile Broadband SystemPublication . Velez, Fernando J.; Correia, Luis M.Multi-service traffic engineering will be a key aspect in cellular planning for Mobile Broadband Systems, the feasibility of the aggregate traffic model being crucial. An MMPP model is proposed for the modelling of the superimposition of data and video IPP sources. Given the correspondence between applications and their bearer service components, an algorithm for the Bernoulli case of the Bernoulli-Poisson-Pascal model is used to compute the blocking probability. The supported number of users is higher in scenarios with a lower maximum load per user. In a cell with 384 channels of 384 kb/s, it varies from 20 to 26 users/cell in urban scenarios, while with 288 channels/cell, although the number of channels is only 25 % lower, the supported number of users decreases 50 %. High terminal mobility strongly degrades the performance in the roads scenario.
- Case Studies for Advancing CR DeploymentPublication . Więcek, Dariusz; Velez, FernandoThis chapter shows selected practical cases studies dealing with advancing CR deployment. Section 6.1 provides details about TV White Space spectrum estimation methodology based on ITU GE06 Plan rules for cases of countries where high levels of TV interference exist. In addition, an example of addressing the practical co-existence of TV white space devices with incumbent applications in the UHF TV band is presented in this section as well. Section 6.2 looks at the practical possibilities of deploying CR systems in the ISM bands, including a techno-economic viability study of CR solutions in factory scenario. Finally, Sect. 6.3 describes a concept and provides an in depth analysis of using CR technologies in medical environments.
- Cognitive radio for medical body area networks using ultra widebandPublication . Chavez-Santiago, Raul; Nolan, Keith E.; Holland, Oliver; De Nardis, Luca; Ferro, João M.; Barroca, Norberto; Borges, Luís M.; Velez, Fernando J.; Goncalves, Vânia; Balasingham, IlangkoWearable wireless medical sensors beneficially impact the healthcare sector, and this market is experiencing rapid growth. In the United States alone, the telecommunications services market for the healthcare sector is forecast to increase from $7.5 billion in 2008 to $11.3 billion in 2013. Medical body area networks improve the mobility of patients and medical personnel during surgery, accelerate the patients’ recovery, and facilitate the remote monitoring of patients suffering from chronic diseases. Currently, MBANs are being introduced in unlicensed frequency bands, where the risk of mutual interference with other electronic devices can be high. Techniques developed during the evolution of cognitive radio can potentially alleviate these problems in medical communication environments. In addition, these techniques can help increase the efficiency of spectrum usage to accommodate the rapidly growing demand for wireless MBAN solutions and enhance coexistence with other collocated wireless systems. This article proposes a viable architecture of an MBAN with practical CR features based on ultra wideband radio technology. UWB signals offer many advantages to MBANs, and some features of this technology can be exploited for effective implementation of CR. We discuss the physical and MAC layer aspects of the proposal in addition to the implementation challenges.
- Multi-Hop Simulator for Ad-Hoc IEEE 802.11ePublication . Ferro, João Miguel; Velez, Fernando JoséAbstract|This work addresses the development of a cross-layer wireless network simulator for IEEE 802.11e in a multi-hop environment. Based on a previous simulator created by our research team for physical plus MAC layers, it involved the upgrade of a previous version of that simulator to model the transmission of packets from the source to the destination using intermediate nodes. From the results obtained for an initial routing algorithm, one can conclude that the system is capable of deliver the packets regardless of the source/destination, and successfully calculate several metrics such as end-to-end delay and number of packets lost.
- Application of Wireless Sensor Networks to the AutomobilePublication . Tavares, Jorge; Velez, Fernando José; Ferro, João MiguelSome applications of Wireless sensor networks (WSNs) to the automobile are identified, and the use of MICAz motes operating at 2.4GHz is considered together with TinyOS support. These WSNs are being conceived in order to measure, process and supply to the user diverse types of information during an automobile journey. Examples are acceleration and fuel consumption, identification of incorrect tire pressure, verification of illumination, and evaluation of the vital signals of the driver. A survey on WSNs concepts is presented, and the wireless sensor network itself (transmitter/receiver/control board) is developed. Aspects of the definition of the architecture and the choice/implementation of the protocols are identified. Security aspects are also addressed, and solutions are proposed.
- Application of Wireless Sensor Networks to the AutomobilePublication . Tavares, Jorge; Velez, Fernando José; Ferro, João MiguelSome applications of Wireless sensor networks (WSNs) to the automobile are identified, and the use of MICAz motes operating at 2.4GHz is considered together with TinyOS support. These WSNs are being conceived in order to measure, process and supply to the user diverse types of information during an automobile journey. Examples are acceleration and fuel consumption, identification of incorrect tire pressure, verification of illumination, and evaluation of the vital signals of the driver. A survey on WSNs concepts is presented, and the wireless sensor network itself (transmitter/receiver/control board) is developed. Aspects of the definition of the architecture and the choice/implementation of the protocols are identified. Security aspects are also addressed.
- Mobile Broadband Systems: Research and VisionsPublication . Velez, Fernando J.; Dinis, Manuel; Ferandes, JoséThis article gives an overview of the European research on Mobile Broadband System (MBS), whose features range from WLANs type scenarios, allowing low mobility and medium data rates, up to public cellular MBS, whre high mobility and data rates are foreseen, leading to plain ubiquity. Current trends in 4G systems are described leading to the defintion of the MBS concept. Owing to high transmission data rate and spectrum limitations at lower frequency bands, MBS intend also to operate at millimetrewave frequency bands, namely the 40 and 60 GHz, offering improves system capacity. The MBS concept and the Trail Platform developed in the framework of the European ACTs-SAMBA and RACE-MBS projects are presented. Cellular planning aspects are discussed including a comparison between the 40 GHz and 60 GHz frequency bands, considering services and applications, tele-traffic, and MBS optimisation based on economics aspects. Field trails resutls on the radio interface performance are presented, demonstrating MBS cellular operation feasibility at millimetrewave frequency bands.
- Insights on Spectrum Sharing in Heterogeneous Networks with Small CellsPublication . Silva, Bruno C.; Sousa, Sofia C.; Teixeira, Emanuel; Velez, FernandoThis work explores the viability of 5G New Radio spectrum sharing in Ultra High Frequency (UHF), Super High Frequency (SHF) and millimetre wavebands(mmWaves) in outdoor environments. In the mmWaves the linear cellular topology is considered while in the UHF/SHF bands cells with hexagonal shape are assumed. Performance evaluation includes the study of the behaviour of PHY and supported throughput for 2.6, 3.5, 28, 38, 60 and 73 GHz. While the two-slope model is considered for the 2.6 and 3.5 GHz frequency bands, the modified Friis propagation model, with shadow fading, and different values for the standard deviation, is the considered in the millimeter wavebands. With sharing, lower system capacity is supported. We clearly observe that, for coverage distances up to circa 100 m, the supported throughput is higher at the millimetre wavebands, mainly due to the reduction that characterizes the application of the two-slope propagation model at the UHF/SHF bands.
- 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.
- System CapacityPublication . Velez, Fernando J.; Nazir, Muhammad Kashif; Aghvami, A. Hamid; Holland, Oliver; Robalo, DanielIn Fixed WiMAX, the contribution from each transmission mode can be incorporated into an implicit formulation to obtain the supported throughput as a function of the carrier-to-interference ratio. This is done by weighting the physical throughput in each concentric coverage ring by the size of the ring. In this paper, multi-hop cells are formed by a central coverage zone and three outer coverage zones served by cheaper low-complexity relays. It is assumed that line of sight propagation to the bases station is achieved in a high percentage of the cell, reducing the impact of selective fading, through allowing dimensioning to be done by GIS cellular planning tools. By using tri-sectorised equipment there is a need for three times more bandwidth, while hardware costs are higher. In our proposal for relays, the FDD mode is considered and the frames need to guarantee resources for BS-to-MS communications but also for BS-to-RS and RS-to-MS communications. These requirements leads to a 1/5 asymmetry factor between the UL and DL in the omnidirectional BS case and to a 3/7 asymmetry factor in the case of tri-sectored BSs. Although the reuse distance is augmented by a factor, we show that with the use of relays in FDD mode only the consideration of tri-sectored BSs with reuse pattern K = 3 (at the cost of extra channels, corresponding to 9 channels) enables to obtain values for the throughput comparable to cases without the use of relays. The presence of sub-channelisation only improves the results for the highest values of R. The consideration of tri-sectored BS antennas with K = 1 (whilst keeping the number of required channels – equal to 3) did not enable to obtain values of the throughput comparable to the ones without using relays, although frame format is more favourable. Relays can be cheaper than BS with full functionalities. As the use of relays may lead to lower costs it is worthwhile to analyse the impact of using them on costs and revenues.