Modelo 2,5D de predição de propagação para ambientes interiores utilizando o método do traçado de raios

A 2.5D ray-tracing propagation model is proposed to predict radio loss in indoor environment. Specifically, we opted for the Shooting and Bouncing Rays (SBR) method, together with the Geometrieal Theory of Diffrartion (GTD). Besides the line-of-sight propagation (LOS), we consider that the radio waves may experience reflection, refraction, and diffraction (NLOS). In the Shooting and Bouncing Rays (SBR) method, the transmitter antenna launches a bundle of rays that may or may not reach the receiver. Considering the transmitting antenna as a point, the rays will start to launch from this position and can reach the receiver either directly or after reflections, refractions, diffractions, or even after any combination of the previous effects. To model the environment, a database is built to record geometrical characteristics and information on the constituent materials of the scenario. The database works independently of the simulation program, allowing robustness and flexibility to model other seenarios. Each propagation mechanism is treated separately. In line-of-sight propagation, the main contribution to the received signal comes from the direct ray, while reflected, refracted, and diffracted signal dominate when the line-of-sight is blocked. For this case, the transmitted signal reaches the receiver through more than one path, resulting in a multipath fading. The transmitting channel of a mobile system is simulated by moving either the transmitter or the receiver around the environment. The validity of the method is verified through simulations and measurements. The computed path losses are compared with the measured values at 1.8 GHz ftequency. The results were obtained for the main corridor and room classes adjacent to it. A reasonable agreement is observed. The numerical predictions are also compared with published data at 900 MHz and 2.44 GHz frequencies showing good convergence

Modulação quantizada para sistemas com codificação wavelet sujeitos ao desvanecimento rayleigh

Wavelet coding is an efficient technique to overcome the multipath fading effects, which are characterized by fluctuations in the intensity of the transmitted signals over wireless channels. Since the wavelet symbols are non-equiprobable, modulation schemes play a significant role in the overall performance of wavelet systems. Thus the development of an efficient design method is crucial to obtain modulation schemes suitable for wavelet systems, principally when these systems employ wavelet encoding matrixes of great dimensions. In this work, it is proposed a design methodology to obtain sub-optimum modulation schemes for wavelet systems over Rayleigh fading channels. In this context, novels signal constellations and quantization schemes are obtained via genetic algorithm and mathematical tools. Numerical results obtained from simulations show that the wavelet-coded systems derived here have very good performance characteristics over fading channels

Avaliação de desempenho da codificação wavelet em canais seletivos em frequência

Wavelet coding has emerged as an alternative coding technique to minimize the fading effects of wireless channels. This work evaluates the performance of wavelet coding, in terms of bit error probability, over time-varying, frequency-selective multipath Rayleigh fading channels. The adopted propagation model follows the COST207 norm, main international standards reference for GSM, UMTS, and EDGE applications. The results show the wavelet coding s efficiency against the inter symbolic interference which characterizes these communication scenarios. This robustness of the presented technique enables its usage in different environments, bringing it one step closer to be applied in practical wireless communication systems

Agroindústria canavieira e unidade de conservação: Impactos Sociais na comunidade de pescadores de Baía Formosa (RN)

The conservation unities emerged in response to the environmental damages. In the Atlantic Forest of the Brazilian Northeast, the most of the damages come from the sugar-cane agro-industry, especially by the deforestation for the introduction of sugar-cane fields and installation of the industry structure. Besides the damages over the biodiversity, there are critical social problems that affect the communities which survive using directly or indirectly the biome from the Atlantic Forest. The objective of this research is to analyze the social impacts on the fishermen of Baía Formosa/RN generated by the changes and socio-environmental transformations occurred starting the installation of a sugar-cane factory and the creation of a conservation area in the municipality of Baía Formosa/RN community. The research is based on a qualitative and diachronic perspective, for both approach, it was used the method of oral history in conjunction with the literature search and some technical and research tools such as direct observation, interview, records images and recordings . The results show that social and symbolic practices of the community in the conservation unit Mata Estrela last more strongly presented. Today fewer natural resources are used, due to factors such as limit access to forest and disappearance of some natural resources by deforestation. It is believed that the loss of free access to space for the community is the most significant negative impact, as promoted changes in the relationship of the community with the Star Forest that contributed to the fading of their social and symbolic practices. The loss of free access caused the decline in the practice of agriculture, which resulted in the loss of one of the means of social reproduction of the community