Multi-dimensional radio channel models for indoor distributed communications

Single- and multi-antenna indoor systems have been designed and used for various applications for some years now, but still there is a room for improvements. Channel modeling is one of the aspects where researchers and engineers face many challenges. Since indoor environments consist of many scatterers, mobility of the nodes introduces non-stationarity in the propagation channel. To enable successful design of communication systems, such an important issue must be taken into account. With that perspective, dedicated measurement campaigns and realistic radio propagation channel models are required in order to exploit fully the improvement potential. The main contributions and findings of this thesis can be summarized as follows: - Three measurement campaigns of indoor-to-indoor radio propagation channels were conducted at 3.8 GHz. - The stationarity period duration varies between 0.8-1.5 s for different investigated cases depending on the environment. - It turns out that small-scale fading within one stationarity period follows a weighted combination of different known distributions. This mixed type of fading can be described by a Second Order Scattering Fading (SOSF) distribution which reflects any combination of Rician, Rayleigh, and double-Rayleigh fading. - New double-ring geometry-based reference and simulation models for narrowband single- and multi-antenna SOSF channels are proposed. Next, second order-statistics of these channels are derived and analyzed. - New model for temporal evolution of angular statistics is proposed. - It is shown that a Hidden Markov Model based approach can be used to reproduce time-variant statistics of small-scale fading. It can be parameterized from measurements: empirical estimation and transition matrices were extracted for the three investigated environments. We observed that predominant fading mechanism can be described by a mixture of Rayleigh and Double Rayleigh distributions. - A methodology of time-variant power delay profiles has been designed in the room-to-room dynamic scenario. - Normal distribution with zero-mean and the variance extracted from measurements can be used for mean large-scale fading modeling and dynamic large-scale fading follows a t-location scale distribution

Physical-statistical modeling of dynamic indoor power delay profiles

This paper presents a physical-statistical radio channel power delay profiles model for room-to-room communication systems combining the room electromagnetic theory for modeling deterministic channel components with a geometry-based stochastic channel model with time-variant statistics for modeling stochastic components. The deterministic channel component, i.e., mean power delay spectrum, is comprised of specularly reflected paths plus diffuse components due to scattering and diffraction. The specular components are modeled with a set Dirac function, whereas the diffuse components modeling approach is a room electromagnetic theory-based model. Dynamic indoor communication channels are characterized by a non-stationary time-and delay-fading process due to changes in the environment. We analyze and model the time-delay variability of channels using K-factor for small-scale variations and the t-location scale distribution parameters for large-scale variations. It turns out that these parameters cannot be assumed to be constant in time and delay. After modeling of time-delay variations of the first order statistics, we generate channel realizations with appropriate second order statistics. As the result, the presented model enables to describe the evolution of the power delay profile in the time domain

Experimental Simulation of Red Sprites in a Laboratory

Over the past three decades, research of high-altitude atmospheric discharges has received a lot of attention. This paper presents the results of experimental modeling of red sprites during a discharge in low-pressure air. To initiate ionization waves in a quartz tube, an electrodeless pulseperiodic discharge fed by microsecond voltage pulses with an amplitude of a few kilovolts and a repetition rate of tens of kHz were formed. In this case ionization waves (streamers) have a length of tens of centimeters. The main plasma parameters were measured at various distances along the tube. The measurements confirm the fact that ionization waves propagate in opposite directions from the zone of the main electrodeless discharge, just as it happens during the formation of red sprites