César Briso

Delay Spread and Electromagnetic Reverberation in Subway Tunnels and Stations

This letter presents an extensive campaign of wideband propagation measurements conducted in a modern subway environment in Madrid, Spain, at 980 and 2450 MHz. Measurements have been made using a channel sounder in a realistic environment of tunnel and station. Based on the measurement results, the principal parameters, such as mean power and delay spread, have been extracted for wideband propagation modeling. Furthermore, the results have been used to model electromagnetic reverberation, quality factor, and transition region between tunnel and station. The quantitative results provide a detailed wideband model of subway environment, as well as determine the design tradeoffs inside real tunnels and stations, in terms of optimal frequency band, antenna position, and expected multipath.

An Automated Emulator of Mobile Satellite Link

This paper decribes the specifications of an automated land mobile channel emulator developed. The system is able to reproduce most of the characteristics of the propagation channel between a real transmitter and receiver, allowing the study of mobile systems and the comprobation of propagation models in the laboratory. Fadding, shadowing, doppler shift, noise increase, multipath and other efects like propagation delays and transponder non linearities can be emulated.

Application of the fractional synthesizers to SFCW radars

An alternative method to generate chirp signals in SFCW-radars based on sigma-delta fractional synthesizers which allow to get high resolutions in a great bandwidth and with high linearity, necessary qualities for the systems SFCW.

An Experimental Propagation Model for LMS Radio Channel using Measurements of GPS Satellite

The purpose of this work is to develop a fast and accurate algorithm to reproduce the received signal variations in land mobile satellite links. This model is going to be used in a hardware emulator to permit test and measurements of different parameters of the channel in laboratory. The model has been generated with measurements of the channel carried out using GPS constellation which is one of the few non geostationary system currently available. The measurements has been been processed to extract the statistics for different environments and elevations of the satellite and a versatile, accurate and easily programmable envelope model has been generated for rural, semi urban, motorway and urban environments

Low Altitude UAV Air-to-Ground Channel Measurement and Modeling in Semiurban Environments

Small- and medium-sized unmanned aerial vehicles (UAVs) can fly for a short distance ( factor model is proposed. The results clearly reveal the existence of two propagation zones with very distinct channel characteristics. The breakpoint indicates the height where the condition of the channel changes rapidly. At low altitudes, the obstacles generate a large amount of multipath and the propagation is greatly affected, while at higher altitudes the influence mitigates. Our results are useful for the modeling of low altitude air-to-ground (AG) propagation channels and the performance analysis of UAV-enabling AG communication systems, such as the channel capacity and the throughput.

Accurate modeling of SMATV networks through "S" parameters

This paper deals with a robust and accurate procedure for the layout and installation of a SMATV network within a building, that takes into account the actual performance of the various modules integrated into the network (head-end, splitters, taps, outlets, etc) working under ¿actual¿ conditions, as compared with the ¿ideal¿ specifications supplied by the manufactures. The proposed methodology is based on the exact characterization of each module in terms of his scattering parameters. Then, the whole network is analyzed with conventional microwave CAD software, under different subscribers loading scenarios in order to derive the robustness of the selected structure. This information can be crucial to the designer to select the most appropriate module for each function to implement into the TV distribution network. To our knowledge little or nothing has been said yet in the literature about this approach.

Reverberation Time in Vehicular Cabins

This paper research is focused on the reverberation time produced inside cabins where the influence of windows on wide-band signals is substantial. This kind of scenarios are important for the new generations of wireless communications since high-density scenarios with high-traffic demand are one of the keys environments. The study presents a preliminary measurement campaign in a close-room of wideband signals in the frequency range between 1.7 to 6 GHz. Based on the measured s21 parameter, the power delay profile has been obtained in order to analyze the diffuse scattering produced inside this particular environment.

Characterization of a Wireless Train Backbone for TCMS

This paper presents a both narrowband and wideband measurement campaign carried out in a Metro environment in order to assess the feasibility of a wireless link for the backbone train communications network. This backbone is the part of the network that links all the vehicles in the consist (A consist is a single vehicle or a group of vehicles that cannot be uncoupled during normal operation.). All the measurements were taken using a channel sounder and also an outdoor-to-indoor link was measured in order to compare with the outdoor-to-outdoor one. The obtained results are the path-loss, power-delay-profiles (PDP), mean delay, RMS spread and also a characterization of the fading is provided.

A Deterministic Two-Ray Model for Wideband Air Ground Channel Characterization

A two-path deterministic model is developed with an analytical dispersion delay computed solution for two common types of flight. From the results, it is deduced that an optimal antenna for the payload communication link in the Ground Station for flat environments should be a λ/4 linear monopole with a ground plane and vertical polarization at a height as close as possible to the ground.

Narrowband Characterization of a Train-to-Train Wireless Link at 2.6 GHz in Metro Environments

A Train-to-Train (T2T) wireless link at 2.6 GHz is characterized for three different metro environments: tunnel, station and open-field. A narrow- band measurement system is used, and obtained attenuation results are analyzed and modeled. The analysis indicates that reflections coming from the environment allow the RF signal to reach higher distances. In this sense, the station environment is the most reflective environment, while the open-field is the opposite situation, and the tunnel an intermediate case. Path-loss models are also obtained for these T2T link; these models allow to estimate the behavior of the link in each metro environment. A statistical analysis of the received signal is also done, and a fit with a log-normal distribution is obtained.