Luiz da Silva Mello

Cognitive radio simulation based on spectrum occupancy measurements at one site in Brazil

A simulation tool was developed to evaluate the performance of cognitive radio systems based on the spectral efficiency achieved. The tool utilizes measurements of spectrum occupancy by primary users as input data. A description of the measurements setup and methodology is presented, as well as the consolidated results of spectral occupancy in frequency bands from 144 MHz to 2690 MHz at one site in Rio de Janeiro, Brazil. Simulation results indicate that cognitive radio efficiency is strongly dependent on occupancy fragmentation. An allocation scheme to improve performance of cognitive radio systems in fragmented frequency bands is proposed.

Simulation of LTE femtocell interference scenarios for cognitive radio implementations

This article presents results of the LTE Femtocell mitigation interference simulations for cognitive radio implementation. The simulations have been performed using the SEAMCAT software at 700 MHz with a 10 MHz bandwidth, considering indoor and outdoor propagation environments. The result is the evaluation of the reduction of cross-tier interference obtained by applying the cognitive radio technology in a femtocell and macrocell network considering different scenarios.

Influence of wind direction on rain attenuation in terrestrial line-of-sight links

In this paper, the influence of wind direction on rain attenuation is investigated based on concurrent measurements of rainfall rate and signal attenuation in converging links with different path lengths, spatial orientations and operation frequencies. A simple but efficient method for predicting the cumulative distribution of rain attenuation in terrestrial line-of-sight links is derived.

Measurements of construction materials penetration losses at frequencies from 26.5 GHz to 40 GHz

This paper presents results of measurements of penetration losses for common construction material in frequencies between 26.5 GHz and 40 GHz. The results are important to the design and deployment of 5G cellular communication systems that will possibly operate in millimeter wave bands, in addition to the currently used frequencies. The penetration losses were in laboratory using a signal generator, two 20 dBi horn antennas and a spectrum analyzer. The materials tested were thin and thick Styrofoam, thin and thick pressed wood, thin and thick solid wood, window glass, a wooden door and a brick wall and measurements show that brick almost completely blocks the millimeter wave signal, causing attenuations up to 64 dB at 34 GHz, whereas the penetration loss is negligible, as expected. Penetration loss in pressed wood and wood significantly depends on the materials thickness.

Comparison of filtering techniques for the analysis of mobile radio channel parameters

This paper presents the results of measurements of wideband channel power delay profiles at 2.5 GHz for an urban environment in Rio de Janeiro, using a multicarrier sounding technique. Data are processed using the CFAR and CLEAN noise filtering techniques and the results are compared.

Preliminary results of measurements of penetration losses through buildings at 2.5 GHz

This article presents the preliminary results of penetration loss of radio waves through the buildings. Measurement campaigns ate 2.5 GHz were performed to obtain empirical data. Based on these results, the specific attenuation factor describing the global effect on the signal that passes through the building was determined for each building investigated. A deterministic model for the prediction of losses was developed and the results were compared with the empirical data.

Statistical characterization and simulation of a femtocell indoor radio channel

This paper presents the statistical analysis of measured propagation data in a femtocell indoor radio environment. Measurements were performed at 1.95 GHz with a 160 MHz channel bandwidth. Time domain sounding technique using PN-sequence with a matched filter was employed. Empirical and theoretical prediction using the Saleh — Valenzuela model and the Finite-Difference Time-Domain (FDTD) method, accelerated via GPU technology, were respectively carried out. So, a comparison between theoretical and experimental simulation is presented.

Power delay profile filtering techniques for indoor radio channel characterization

This paper presents a comparison of two power delay profile filtering techniques, the Relevance Vector Machine — RVM — and the Constant False Alarm Rate — CFAR. Both techniques are applied to power delay profiles (PDPs) measured in a indoor environment at 1.95 GHz on a 160 MHz channel bandwidth and the matched filter technique is used for the sounding. The RMS (root mean square) delay spreads are determined from these filtered PDPs and from the original ones. So, for all positions of the receiver, they are compared and the quadratic mean error is evaluated.

Experimental evaluation of time domain energy detection for cognitive radio applications

This article presents results of the evaluation of the energy detection technique that can be used for the implementation of cognitive radio DSA (Dynamic Spectrum Allocation). The experimental data consists of received signal measurements at geo-positioned points different routes in a urban area, when OFDM signals are transmitted in 3.5 MHz channels with the central frequency of 3,44 GHz. The results are the evaluation of the detection error and the possibility of secondary use of the spectrum along the measurement routes.