Modeling and characterization of urban radio channels for mobile communications

Results of this thesis contribute in modeling and characterization of radio channels for future mobile communications. The results are presented mainly in three parts: a) modeling of propagation mechanisms, b) methodology of developing a propagation model, c) characterization of urban radio channel. One of the main propagation physical phenomena that have an important role in diverting signals to non line of sight scenarios is the diffraction process. This thesis proposes diffraction coefficients that have better agreement with finite difference time domain solution and rigorous diffraction theory than the coefficient commonly used in propagation predictions for mobile communications. The importance of diffuse scattering has also been investigated and showed that this physical process may have a key role in urban propagation, with a particular impact on the delay spread and angular spread of the signal at the receiver. This thesis proposes wideband propagation models for main and perpendicular streets of urban street grids. The propagation models are ray-based and are given in explicit mathematical expressions. Each ray is characterized in terms of its amplitude, delay, and angle of arrival, angle of departure for vertical and horizontal polarizations. Each of these characteristics is given in a closed mathematical form. Having wideband propagation model in explicit expression makes its implementation easy and computation fast. Secondary source modeling approach for perpendicular streets has also been introduced in this thesis. The last part of the thesis deals with characterization of urban radio channels for extracting parameters that help in successful design of mobile communication systems. Knowledge of channel characteristics enables reaching optimum trade off between system performance and complexity. This thesis analyzes measurement results at 2 GHz to extract channel parameters in terms of Rake finger characteristics in order to get information that helps to optimize Rake receiver design for enhanced-IMT2000 systems. Finger life distance has also been investigated for both micro- and small cell scenarios. This part of the thesis also presents orthogonality factor of radio channel for W-CDMA downlink at different bandwidths. Characterization of dispersion metrics in delay and angular domains for microcellular channels is also presented at different base station antenna heights. A measure of (dis-) similarity between multipath components in terms of separation distance in delay and angular domains is introduced by the concept of distance function, which is a step toward in development of algorithm extraction and analysis multipath clustering. In summary, the significant contributions of the thesis are in three parts. 1) Development of new diffraction coefficients and corrections of limitations of existing one for accurate propagation predictions for mobile communications. 2) Development of wideband propagation models for urban street grid. The novelty of the model is the development in explicit mathematical expressions. The developed models can be used to study propagation problem in microcellular urban street grids. 3) Presenting channel parameters that will help in the design of future mobile communication systems (enhanced-IMT2000), like number of active fingers, finger life distance, and orthogonality factors for different bandwidths. In addition, a technique based on multipath separation distance is proposed as a step toward in development of algorithms for extraction and analysis of multipath clusters.reviewe

Wideband mobile propagation channels: Modelling measurements and characterisation for microcellular environments

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Mobile WiMAX system performance – simulated versus experimental results

This paper addresses the downlink performance of mobile WiMAX operating at 2.3GHz in an urban environment. The analysis includes a comparison of simulated and experimental results. Simulated packet error rate (PER) versus Signal to Noise Ratio (SNR) graphs are generated on a per link-speed basis using a fully compliant 512 carrier mobile WiMAX simulator. Experimental data is gathered using a carrier-class basestation, a mobile-WiMAX enabled laptop, and a suite of application layer logging software. An H264 AVC encoder and IP packetisation unit is used to transmit video to a mobile client. Results show strong agreement in terms of simulated and captured PER. Using this data, the downlink operating range is evaluated as a function of the Effective Isotropic Radiated Power (EIRP) and path loss exponent. Results indicate that at low EIRP (32 dBm) the expected outdoor operating range is around 200-400m. Applying the UK OFCOM regulations for licensed operation in the 2.5GHz band, downlink operation in excess of 2km can be achieved

On the Frequency Dependency of Radio Channel's Delay Spread: Analyses and Findings From mmMAGIC Multi-frequency Channel Sounding

This paper analyzes the frequency dependency of the radio propagation channel's root mean square (rms) delay spread (DS), based on the multi-frequency measurement campaigns in the mmMAGIC project. The campaigns cover indoor, outdoor, and outdoor-to-indoor (O2I) scenarios and a wide frequency range from 2 to 86 GHz. Several requirements have been identified that define the parameters which need to be aligned in order to make a reasonable comparison among the different channel sounders employed for this study. A new modelling approach enabling the evaluation of the statistical significance of the model parameters from different measurements and the establishment of a unified model is proposed. After careful analysis, the conclusion is that any frequency trend of the DS is small considering its confidence intervals. There is statistically significant difference from the 3GPP New Radio (NR) model TR 38.901, except for the O2I scenario.Comment: This paper has been accepted to the 2018 12th European Conference on Antennas and Propagation (EuCAP), London, UK, April 201

Modelado de canal inalámbrico empleando técnicas de trazado de rayos: Una revisión sistemática

This paper presents an analysis of the research conducted by the scientific community who report similar characteristics in their evaluation. Predictions based on the use of computational tools that improve response times with acceptable accuracy. These calculations are corroborated by extensive measurement campaigns at specific sites in order to demonstrate the hypothesis. Finally the results were analyzed for each situation presented.Este trabajo presenta un análisis de las investigaciones realizadas por la comunidad científica que reportan características similares en su evaluación. Predicciones basadas en el uso de herramientas computacionales que mejoran cada vez los tiempos de respuesta con precisiones aceptables. Estos cálculos han sido corroborados a través de extensas campañas de medición en sitios específicos con el fin de evidenciar las hipótesis. Finalmente se exponen los resultados para cada situación analizada

Packet Loss in Terrestrial Wireless and Hybrid Networks

The presence of both a geostationary satellite link and a terrestrial local wireless link on the same path of a given network connection is becoming increasingly common, thanks to the popularity of the IEEE 802.11 protocol. The most common situation where a hybrid network comes into play is having a Wi-Fi link at the network edge and the satellite link somewhere in the network core. Example of scenarios where this can happen are ships or airplanes where Internet connection on board is provided through a Wi-Fi access point and a satellite link with a geostationary satellite; a small office located in remote or isolated area without cabled Internet access; a rescue team using a mobile ad hoc Wi-Fi network connected to the Internet or to a command centre through a mobile gateway using a satellite link. The serialisation of terrestrial and satellite wireless links is problematic from the point of view of a number of applications, be they based on video streaming, interactive audio or TCP. The reason is the combination of high latency, caused by the geostationary satellite link, and frequent, correlated packet losses caused by the local wireless terrestrial link. In fact, GEO satellites are placed in equatorial orbit at 36,000 km altitude, which takes the radio signal about 250 ms to travel up and down. Satellite systems exhibit low packet loss most of the time, with typical project constraints of 10−8 bit error rate 99% of the time, which translates into a packet error rate of 10−4, except for a few days a year. Wi-Fi links, on the other hand, have quite different characteristics. While the delay introduced by the MAC level is in the order of the milliseconds, and is consequently too small to affect most applications, its packet loss characteristics are generally far from negligible. In fact, multipath fading, interference and collisions affect most environments, causing correlated packet losses: this means that often more than one packet at a time is lost for a single fading even

Medium- and large-scale characterization of UMTS-allocated frequency division duplex channels

A dual-band sounder is used in both trolley and van measurements in the dense urban environment of Manchester city center to characterize the uplink (1920-1980 MHz) and downlink (2110-2170 MHz) frequency-division duplex (FDD) channels allocated to third-generation (3G) mobile radio systems. The data are analyzed with 60- and 5-MHz resolutions, as used for 3G wideband code-division multiple-access systems. Root-mean-square (rms) delay spread and 15-dB widths of mainly temporally averaged delay profile are presented either as cumulative distribution functions (cdfs) for each individual frequency band or as histograms of the difference between uplink and downlink on a local area basis. It was found that the histograms show larger differences between the two bands than the individual cdf and that the differences between the FDD channels are more pronounced on circumferential routes and shadowed locations. Correlations of rms delay spread with excess path loss and distance are on the order of 0.5 and 0.4, respectively