CROSSNET - Cross-layer and Network Planning for B3G Systems

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Publications

Publication . Velez, Fernando J.; Sebastião, Pedro; Costa, Rui; Robalo, Daniel; Comissário, Cláudio; Rodrigues, António; Aghvami, A. Hamid

This 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.

2010-02Book part

Open access

Modelling and simulation of B3G multi-service traffic in the presence of mobility

Publication . Juárez, Jesús M.; Paulo, Rui R.; Velez, Fernando J.

A multi-service traffic model is proposed, and its validation is achieved by using event-based simulation results which consider the burstiness of traffic. By considering the deployment scenarios and tele-traffic parameters from the Vehicular scenario of IST-SEACORN, a simulator was produced to extract conclusions about blocking and handover failure probabilities. Simulations, were performed for different cases, from single- to multi-service situations, and from absence to presence of mobility. Besides results for the quality of service in the air interface, including blocking and handover failure probabilities for several types of traffic, the simulator allows for extracting conclusions about the validation of the Bernoulli/Poisson/Pascal model for the computation of the on/off blocking probability, the ratio between the number of session rejected at the beginning of an on period and the total number of bursts generated during a session. In the single-service case, the theoretical and the experimental values of on/off blocking probability are close to each other. An almost perfect concordance between theoretical and simulation values is verified when the average sojourn time in cells is equal to the average holding time. In the multi-service case, although the results are not exactly coincident a coherent behaviour is achieved for an average traffic per user up to 0.06 Erl.

2009Journal article

Open access

Classificação de aplicações e cenários de operação em UMTS melhorado

Publication . Franco, Cátia; Rei, Ricardo; Velez, Fernando J.; Ferreira, Jaime

Terceira geração (3G) é o termo genérico utilizado para a geração de sistemas móveis de telecomunicações imediatamente posterior ao GSM. Os sistemas 3G procuram garantir melhores serviços para a transmissão de voz, textos e dados. O Sistema Universal de Telecomunicações Móveis (UMTS  Universal Mobile Telecommunications System) é parte do sistema global de comunicações de terceira geração da União Internacional de Telecomunicações (ITU). A 3G foi baseada na norma GSM actual, porém evoluída, estendida e melhorada de forma a incluir novas especificações para a interface ar mais adequada para os serviços de alta velocidade e multimédia. Este sistema permite que os utilizadores da segunda geração, GSM, migrem facilmente para os serviços de terceira geração. O UMTS padrão pertence à terceira geração de redes móveis. O objectivo primordial da 3G é a realização de uma estrutura universal capaz de suportar tanto os serviços existentes como os futuros. A 3G está normalizada pelas sociedades 3G Partnership Projects: 3GPP (na Europa) e 3GPP2 (nos EUA). Os conceitos tecnológicos para os sistemas 3G continuam em desenvolvimento e proporcionaram já a definição da geração 3.5, em que se inclui o UMTS Melhorado (E-UMTS), uma rede totalmente IP (All-IP) que pretende assegurar maior capacidade, flexibilidade na rede nuclear de suporte (core network) e utilização de serviços integrados suplementares. Dada a complexidade das redes UMTS e E-UMTS, nem sempre é possível desenvolver modelos analíticos simples para projectar e planear o sistema. Para ultrapassar essas dificuldades recorre-se frequentemente a simulações, que se baseiam num desenho topológico existente ou planeado, numa estimativa da distribuição do tráfego e numa variedade de serviços com múltiplos requisitos de qualidade de serviço (QoS), o que constitui uma grande diferença relativamente às redes de segunda geração.

2005-03Journal article

Open access

Service Suitability Based RAT Selection for Beyond 3G Systems

Publication . Rodriguez, J.; Monteiro, V.; Bastos, J.; Gameiro, A.; Cabral, Orlando Manuel Brito; Velez, Fernando

In beyond 3G systems, one of the important factors is to address Radio access technology (RAT) selection and load balancing between heterogeneous networks to ensure high spectral efficiency in an era where spectral resources are at a premium. This work aims to address the feasibility of utilizing WiFi as complementary service for HSDPA, to prevent quality of service deterioration in the event of network overload in HSDPA during the busy period. The proposed RAT selection algorithm is based on the load of each system, and the results show that the outage probability can be improved by up to 45% relative to a stand-alone HSDPA system.

2008Conference object

Open access

Planning and Deployment of WiMAX and Wi-Fi Networks for Health Sciences Education

Publication . Sebastião, Pedro; Velez, Fernando J.; Costa, Rui; Robalo, Daniel; Comissário, Cláudio; Rodrigues, António

Optimal 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.

2009Journal article

Open access