Graduate School and Research Center In communication systems

# Indoor UWB channel characterization and modeling based on an information theoretic approach and SAGE algorithm

Models of radio channel propagation are indispensable in the analysis and design of wireless communication systems. They are used to predict power and interference levels and analyze other properties of the radio link. The main goal of this dissertation is to provide a set of tools that allow the researchers in the field of Ultra Wide Bandwidth (UWB) communication systems to investigate the performances of those proposed algorithms and communication system schemes. Based on a set of UWB channel (from $3$ to $9$ GHz) measurements under both Line of Sight (LOS) and Non Line of Sight (NLOS) conducted recently at Eurecom Institute. A Vector Network Analyzer is used to measure the frequency channel response of the frequency bandwidth of interest. An Omnidirectional antennas are used for both the transmitter (Tx) and receiver (Rx) antennas. Probability and cumulative density of received signal, power variation and path–loss fluctuations are evaluated. An estimation of m-parameter for each delay and its probability density function are given away (for NLOS). We have find that the Weibull power density function (pdf) fits the experimental measurements. Besides, an investigation of path–loss shows no dependency between frequency and the path–loss, but the path–loss and central frequency present a correlation. We have also found that most measurements characterized by a shadowing fading fit a lognormal distribution and the small fading distribution seemed to have a value of $\tilde = 1$, which corresponds to a Rayleigh distribution. In the second part of this thesis we use a new approach for characterizing the second-order statistics of indoor UWB channels using channel sounding techniques. These are based on an eigen-decomposition of the channel auto-covariance matrix, which allows for the analysis of the growth in the number of significant Degrees of Freedom (DoF) of the channel process as a function of the signaling bandwidth as well as the statistical correlation between different propagation paths. We show empirical eigenvalue distributions as a function of the signal bandwidth for both LOS and NLOS situations. Moreover, we give examples where paths from different propagation cluster show strong statistical dependence. And to confirm the saturation of DoF with channel bandwidth increasing, the theoretic information is used. Firstly we evaluate the number of DoF using AIC and MDL, and secondly we investigate the channel entropy. In the UWB propagation context, a physical phenomenon must be taken in consideration. Analyzing these phenomena the UWB radio channel is affected by various propagation mechanisms, particularly reflection, transmission, scattering and diffraction. We have analyzed by multiplicity of simulations of the diffractions and reflections as function of channel bandwidth, the materiel properties and the displacements types. After that, we have proposed a new UWB channel model. The presented model is, in fact, based on physical propagation effects and UWB channel measurements conducted at Eurecom. In order to do this, a Space Alternating Generalized Expectation Maximization (SAGE) algorithm is used to estimate the model parameters. The Simulations show that the proposed model presents a good fit to measurement data and is easy to implement.