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

Ellipticity Statistics of Ultra Wideband MIMO Channels for Body Centric Wireless Communication

In this paper, ellipticity statistics of 2 × 2 ultra wideband multiple-input-multiple-output (MIMO) channel for body-centric wireless communication is evaluated by quantifying four different on body links namely; waist-back, waist-chest, waist-ankle and waist-wrist. Results show that at lower values of signal to noise (SNR), spatial multiplexing dependent capacity degrades as the eigen value dispersion decreases (i.e., lower ellipticity statistic), whereas it increases at higher values of SNR

Fast Path Loss Prediction By Using Virtual

This work proposes a new principle for fast path loss prediction and cell coverage calculations for urban microcells in high rise building environment. The technique is based on finding a virtual source located in line of sight with the mobile station (MS). This technique maps the out-of-sight propagation prediction problem to a line-of-sight propagation prediction problem. The received power at MS is given in a closed form expression. Based on comparison performed with experimental results, it seems that breakpoint is valid in side-street propagation. The proposed virtual source principle opens a door for a new fast computation technique for path loss modeling in the microcellular environment

Modeling of Fading Figure for Non-stationary Indoor Radio Channels

Fading models of practical mobile radio channel may change over time and/or due to mobility being Rice, Rayleigh, double-Rayleigh, etc, depending on the nature of radio wave propagation, which results in a non-stationary channel. This work is based on investigation of fading figure (FF) that addresses non-stationarity nature of radio channels. The FF is represented by the parameter m of Nakagami-m distribution. For an indoor environment system, our results show the parameter m, which can be modeled as a generalized extreme value distribution. The statistical distribution model of parameter m can be used to study performance of wireless communication system under non-stationary radio channels

Investigations Of Controlling Propagation Characteristics Using

This work proposes a propagation control technique for mobile communications in microcellular environment. Transmitting array antennas at the base station are utilized for controlling propagation characteristics. The propagation control technique can be used for interference reduction between neighboring cells and controlling the coverage area size (e.g., controlling propagation slope). Five propagation control methods are suggested. Three schemes are tested here, the antenna arrangement, the phase excitations and the displacements between antennas