This paper presents an architecture proposal for a spectrum sensing network using software defined radios. The radios responsible for the sensing are implemented with SDR-RTL, a low-cost radio, capable of receiving signals from several frequency bands, such as those used in FM, DAB and DVB-T. Sensing functions are implemented using GNU Radio, the most commonly used free software for configuring software-defined radios installed in Raspberry Pi’s, which makes the sensing structure significantly compact and inexpensive when compared to other solutions. Experiments are performed to measure the probability of detection in relation to the signal noiseratio, as a metric of the efficiency of the system proposed in this work

Wireless Sensor Networks (WSNs) have become an area of great interest due to their usage in a wide range of applications. A preliminary study concerning the viability of a WSN introduced in the environment is recommended, considering that this type of network is applied with several variables that influence the operation of the network. Those variables directly affect the network performance metrics such as the Received Signal Strength Indicator (RSSI). The present paper provides a study about the application of a WSN on a specific environment to practice sports, in which the RSSI metric was used to study the link quality. The study uses several power prediction models, and the results were compared with real measurements in order to identify the best prediction model in this particular environment.

Propagation in Radiofrequency is a constant concern in the application of Wireless Sensor Networks (WSN), the behavior of an environment determines how good the quality of signal reception. The sensor network environment suffers undesirable effects which affect the communication between the modules, the correct modeling of environmental effects is the realized by received power prediction that is important for the deployment in the desired environment. The objective of this paper is to analyze the behavior of a WSN applied in Brazilian forests and places of beans agriculture, where environmental variables are present, and correlate the captured values of received signal strength (RSSI) with models to power prediction in WSN, and show the best model for this application.

Wireless Sensor Networks (WSN) are already trend in many applications, environmental modeling in this network is of fundamental importance to maintain communication between modules always in acceptable power transmission and reception levels. Faced with this challenge the aim of this work is to conduct a study on the propagation of radio frequency signals in WSN applied in an environment used as water reservoir, this analysis will be done by comparing the real values Received Signal Strength Indicator (RSSI) with the estimates proposed by some of the most used power prediction models for WSN, thus achieving the best modeling of the proposed environment and thus determine which power prediction model more suitable for the application.

Mobile devices are increasingly occupying sectors of society and one of its most important features is mobility. However, the use of mobile devices is subject to the lifetime of the batteries. Thus, the use of energy batteries has become an important issue in the study of wireless network technologies. In this context, new solutions that enable aggregate energy efficiency not only through energy saving, and principally they are evaluated from a more realistic model of energy discharge, if easy adaptation to existing protocols. This paper presents a study on the energy needed and the lifetime for Wireless Sensor Networks (WSN) using a heterogeneous network and applying the LEACH protocol.

Cognitive radio is a viable technology for the next generation of wireless communications. The ability to sense the electromagnetic spectrum and to enable vacant bands to other users has been investigated in the past years. One important issue is the use of an efficient spectrum sensing algorithm to monitor the frequency band occupancy. Usually, the effects of fading are overseen in the analysis of those algorithms. This paper aims to evaluate the performance of a spectrum sensing algorithm based on Jarque-Bera test. Rayleigh fading is considered in this paper. Preliminary simulation results are provided, to demonstrate the potential of the proposed strategy.

Spectrum sensing is a basic mechanism for Cognitive Radios to find unused spectrum bands.Sensing based on energy detection has been proposed and widely used because it requires no information about the transmission of the primary user, therefore it is a blind system.This paper presents a method for blind spectrum sensing based on a statistical test.The proposed system has a higher detection probability than the system based on energy detection and also than the system based on another statistical test described in the literature, for the same number of samples.

This paper presents an analysis of spectrum sensing to determine if a signal, measured by a cognitive user in an AWGN channel, is a valid one, from the primary user, or if it is composed of noise alone. The proposed method for spectrum sensing is based on statistical tests to identify if the probability distribution of the received signal has noise characteristic, or other distribution that classifies it as a primary user. The results of Monte-Carlo simulations indicate that it is possible to identify transmission opportunities using spectrum sensing tests with low signal-to-noise ratio.

The use of mobile phones has been the target of a great controversy due to possible biological and behavioural effects. This research presents a preliminary evaluation, regarding the learning and stress levels in subjects of the species Rattus norvegicus, submitted to microwave radiation. The psychological analysis was based on laboratory tests using the aquatic maze (tank of Morris), to determine the capacity of learning and memorisation and the elevated cross maze, designed to evaluate the levels of anxiety and stress. The consumption of water and food was monitored as well as the weight of the animals. The experiments were accomplished using irradiated rats (Experimental Group), and non-irradiated rats (Control Group). No significant differences were observed in the learning or performance of the groups in the aquatic maze experiment. For the elevated cross maze tests, the subjects of the Experimental Group manifested lower stress levels.

fator de carga, número de usuários atendidos simultaneamente, razão portadora-interferência e potência média de transmissão das estações radiobase

This paper presents an algorithm to evaluate the performance of the Universal Mobile Telecommunication System (UMTS), which will soon be deployed in Brazil. The proposed UMTS physical layer simulation system is described. The block diagram for the simulator architecture is presented. A functional description for some of the blocks is included and some results are presented.