Gláucio Lima Siqueira

Local and Global Signal Variability Statistics in a Mobile Urban Environment

Signal variability in mobile radio communicationenvironments has been extensively studied. It isalways assumed that, for small areas, thevariability is Rayleigh-distributed, althoughexperimental results have proven that this is notalways the case. Other distributions present moreaccurated results. For large areas, the Suzukidistribution has been proposed based on the Rayleighassumption. This work presents a review of the mostcommonly used distributions for the local and globalstatistics of the received signal variability andthe theoretical foundation for a generalizeddistribution for large areas based on the assumptionof a Weibull distribution for short-termvariability. All distributions are presented in alinear and logarithmic form to facilitate comparisonwith experimental data. This new proposeddistribution gives better accuracy than the Suzukidistribution.

On the Use of Wavelet-Based Denoising to Improve Power Delay Profile Estimates from 1.8 GHz Indoor Wideband Measurements

This work presents an alternative processing scheme to improve measurement-based power delay profiles (PDP) estimates, using wavelet-based denoising. The usual PDP processing comprises cutting off all the data below a previously determined flat noise threshold. The proposed method is a more refined approach, since it tries to extract the noise from the measured data, keeping only the estimated signal. Wavelet denoising can be performed in many different ways, for it depends on several parameters, like the noise threshold selection rule, the wavelet function, the choice or not for a wavelet coefficients shrinkage and the number of decomposition levels. Several parameter combinations have been tested, in special for the Visu selection rule, which presented the best performance for the available data in the overall. Denoising was applied to real data from indoor environments, collected from wideband channel sounding surveys, centered at 1.8 GHz. Since frequency domain sounding has been carried out, denoising has been tested both directly over the frequency domain, and over the time–delay domain (PDP). The major result of the proposed processing was a qualitative improvement of the PDP, with smoother noise floors, and also with increases up to 8 dB on signal-to-noise ratios, in special for delay domain denoising.

Mobile indoor wide-band 1.8 GHz sounding: measurement-based time dispersion analysis

The results of a 1.8 GHz indoor wideband channel sounding survey in some typical environments, trying to account for pedestrian subscriber mobility, are presented. The sounding technique has been based on the classical frequency domain, with an optic link instead of coaxial cables providing an extended path range, up to 350 m. Three different scenarios have been analyzed. Complete small and large-scale time dispersion analysis have been derived from the impulse responses measured, like mean delay, rms delay spread, coherence bandwidth and its variations with mobility. From the whole analysis carried out, two main results are worth remarking upon: the power delay profile variation with distance providing a pictorial representation of the main scattering mechanisms of the environment; and the validation of a lower bound relation between the coherence bandwidth and the rms delay spread.

Propagation measurements of a 3.5 GHz signal: path-loss and variability studies

The results of propagation measurements of a 3.5 GHz signal realized on a typical urban environment at Rio de Janeiro city are presented. The path-loss, obtained from two different urban environments, is calculated and compared with the most popular prediction models in the literature. Variability characteristics such as the large-scale fading and small scale fading of the envelope of a received signal are estimated from some known probability functions. The obtained statistics together with other such the level crossing rate (LCR) and average fade duration (AFD) formulations are also compared with the results obtained from the measurement data.

Relationship between delay spread and coherence bandwidth for UWB transmission

In this paper we present the results of an ultra wideband (UWB) measurement campaign carried out in an indoor environment. The UWB channel parameters were evaluated from the measured data. Specially, temporal dispersions of the multipath channel were calculated and the relationship among these parameters was studied. The sounding technique was based on the classical frequency domain over a bandwidth of 850 MHz. The temporal dispersions in the mobile radio were assessed in terms of the delay spread and coherence bandwidth.

A Site-Specific Beam Tracing Model of the UWB Indoor Radio Propagation Channel

A site-specific convex pyramidal beam tracing model of ultrawideband (UWB) indoor propagation channels is described in detail. The model is fast and accurate, since it does not need to apply nontrivial and costly tests to determine all the existing rays between the transmitter and receiver. Predictions from the model are compared with those from corresponding measurements, performed under line-of-sight (LOS) and nonline-of-sight (NLOS) conditions. A good agreement is displayed between predicted and measured impulse responses, as well as of some derived parameters (average power, mean delay, and delay spread), as they vary with the distance between the transmitter and the receiver.

Indoor signal coverage of a leaky feeder cable

Recently the use of the leaky feeder cable became increasingly important for signal coverage in indoor environments as universities, shoppings and mines. Moreover, a radiating cable can be considered as a possible solution in emergency staircases or elevator shafts. This motivated to carry out measurements that led to studying the signal behavior along a corridor in the fourth floor of Federal Fluminense University Engineering building where it is installed. Besides the large scale fading, the signal coverage was studied for points below the cable and beyond the cable.

Coverage prediction models fitted to the signal measurements of digital TV in Brazilian cities

Broadcast television is one of the most important telecommunications systems in Brazil. Such relevance in the socio-cultural context requires a continuous pursuit of technical excellence in order to offer an increasingly attractive product to the viewer. Therefore, it is mandatory to care about the coverage and quality of the TV signal, especially when it comes to Digital TV. In this scenario, it is imperative to study propagation models to predict the coverage allowing broadcasters to properly project their stations and regulators to distribute the channels harmoniously. The aim of this study is to compare the field strength measurements of a Digital TV signal in five cities of Brazil, with the values predicted by some models and to conclude for the best one.

Comparison Between OFDM and STDCC Mobile Channel Sounders at 3.5 GHz

In this paper, we present a comparison between OFDM and STDCC sounding techniques used to wide band channel characterization in suburban environments at 3.5 GHz band. Measurements of the received signals power delay profile and power level for each of the sounding techniques were obtained. These experimental results are presented and compared. For this comparison, important wide band characterization information are obtained and the performances of each one of used techniques are observed.

Channel characterization in the 5.8GHz band in a suburban area

Based on signal measurements carried out in the 5.8 GHz band, which is reserved for unlicensed WiMAX in Brazil, this paper evaluates narrowband and wideband characteristics on the suburban area of Tangua city in Rio de Janeiro State. Fading statistics, coverage and adjusted prediction model such as Hata-COST 231, SUI and UFPA were used in order to find the model that best fits the measurement data before ultimately determining that the UFPA model proved to be the best one. Temporal dispersion is studied through the delay spread and coherence band calculated from the power delay profiles obtained in the sounded channel.