On the correlation and ergodic properties of the squared envelope of SOC Rayleigh fading channel simulators

In this paper, we investigate the correlation and ergodic properties of the squared envelope of a class of autocorrelation-ergodic (AE) sum-of-cisoids (SOC) simulation models for mobile Rayleigh fading channels. Novel closed-form expressions are presented for both the ensemble and the time autocorrelation functions (ACFs) of the SOC simulation model’s squared envelope. These expressions have been derived by assuming that the SOC model’s inphase and quadrature (IQ) components have arbitrary autocorrelation and cross-correlation properties. This consideration makes the results herein presented more general than those given previously in other papers, where it is assumed that the IQ components of the simulation model are strictly uncorrelated. We show that under certain conditions, the squared envelope of the SOC model is an AE random process. In addition, we evaluate the performance of three fundamental methods for the computation of the model parameters—namely the generalized method of equal areas, the L p -norm method, and the Riemann sum method—regarding their accuracy for emulating the squared envelope ACF of a reference narrowband Rayleigh fading channel model. The obtained results are important to design efficient simulators for the performance analysis of systems and algorithms sensitive to the correlation properties of the channel’s squared envelope, such as speed estimators and handover mechanisms

Channel simulation models for mobile broadband communication systems

Mobile broadband wireless communication systems (MBWCS) are emerging as a solution to provide broadband services to users on the move. These systems are expected to operate in a wide variety of propagation scenarios, at different mobile speeds, and at various frequency bands. Under such a variety of requirements, flexible and efficient channel simulation models will prove fundamental for the laboratory analysis of MBWCS. Currently, most of the existing channel simulation models are either too complex as to allow for an efficient performance investigation of MBWCS, or they cannot be applied to the simulation of some relevant classes of mobile fading channels. To overcome these limitations, we present in this doctoral a flexible and efficient methodology for the design of channel simulation models for MBWCS. Such a methodology is based on the sum-of-cisoids (SOC) approach, an approach that is closely in line with the electromagnetic plane-wave propagation model. We build our channel simulators upon a class of ergodic SOC simulation models. For the computation of the SOC model parameters, we introduce two simple methods that enable the design of simulation models for mobile fading channels characterized by any type of Doppler power spectral densities (DPSDs). The proposed methods are well-suited for the simulation of both single-input single-output (SISO) and multiple-input multiple-output (MIMO) channels. We evaluate the methods’ performance with respect to their accuracy for emulating important statistical functions of the channel, such as the autocorrelation function (ACF), the envelope probability density function (PDF), and the ACF of the squared envelope. In the case of MIMO channels, we evaluate the methods’ performance in terms of the approximation of the channel temporal ACF and spatial cross-correlation function (SCCF). The obtained results demonstrate the excellent performance of the proposed methods. This dissertation is also intended to provide a comprehensive treatise of the theory behind the design of SOC simulation models for mobile fading channels. In this respect, the statistical properties of SOC channel simulators are thoroughly analyzed. Important contribution are given concerning the correlation properties of the square envelope of SOC simulators. Such contributions include the derivation of closed-form expressions for the squared envelope ACF of the SOC simulation model, and the analysis of the ergodicity properties of the SOC model’s squared envelope. We also revisit here the concept of the symbol-spaced tapped line model (SSTDL) for WSSUS channels. In this regard, we present a discussion on the problems of SSTDL models, and we propose a simple solution to avoid them. The usefulness of such a solution is exemplary demonstrated by analyzing the bit error probability of a multi-carrier code division multiple access (MC-CDMA) system

A Novel Simulator of Nonstationary Random MIMO Channels in Rayleigh Fading Scenarios

For simulations of nonstationary multiple-input multiple-output (MIMO) Rayleigh fading channels in time-variant scattering environments, a novel channel simulator is proposed based on the superposition of chirp signals. This new method has the advantages of low complexity and implementation simplicity as the sum of sinusoids (SOS) method. In order to reproduce realistic time varying statistics for dynamic channels, an efficient parameter computation method is also proposed for updating the frequency parameters of employed chirp signals. Simulation results indicate that the proposed simulator is effective in generating nonstationary MIMO channels with close approximation of the time-variant statistical characteristics in accordance with the expected theoretical counterparts

Design of Mobile Radio Channel Simulators Using the Iterative Nonlinear Least Square Approximation Method with Applications in Vehicle-to-X Communications

Doktorgradsavhandling i informasjons- og kommunikasjonsteknologi, Universitetet i Agder, 2015Vehicle-to-X (V2X) communication systems are expected to provide tremendous benefits associated with the safety and traffic efficiency on roads. The successful deployment of emerging technologies like V2X requires channel models accurately representing fading statistics in environments where those technologies are used. The accuracy is, of course, a major concern when adapting or developing a suitable channel model for test and evaluation purposes. However, it is also important to take into account the simplicity of a channel model, which is crucial for efficient numerical computations and computer simulations. Reconciling simplicity and accuracy is a rather complex task to accomplish, which requires sophisticated parameter computation methods. To the best of our knowledge, only a limited number of investigations address the channel modelling and parametrization problems for vehicular propagation scenarios in the literature. In order to fill this gap, we concentrate on the development of new sophisticated channel modelling approaches and efficient parameter computation methods for the design of V2X communication systems in this dissertation. In general, there are two main applications of channel models: (1) for the design and test of wireless communication systems and (2) for the optimization of existing communication systems. For the design and test purposes, more general statistical models such as Rice and Rayleigh channel models are preferred. Those channel models provide a fundamental insight into propagation phenomena and at the same time they greatly simplify the theoretical and numerical computations to assess the performance of wireless communication systems. For the optimization purposes, however, measurement-based channel models are commonly used. The main advantage of such channel models is that they always accurately reflect the physical reality. In this dissertation, we will focus on the channel models designed for both of those application purposes. A significant part of this dissertation will be devoted to the thorough analysis and design of Rayleigh and Rice fading channel models. We investigate the correlation properties of those channels assuming asymmetrical shapes of Doppler power spectral densities (PSDs). In fact, this is what we often observe in real-world propagation scenarios. In this regard, we will present an analytical expression for the autocorrelation function (ACF) of Rice processes that captures such realistic scenarios. Another important contribution to this topic is the novel iterative nonlinear least square approximation method for the design of Rice and Rayleigh channel simulators based on sum-of-sinusoids (SOS), as well as sum-of-cisoids (SOC) approaches. The idea behind the proposed method is very simple. The parameters of the simulation model are extracted from the reference model, such as the stochastic Rice and Rayleigh channel models, by fitting the statistical properties of interest, e.g. the ACF and the probability density function (PDF). We show that the proposed method outperforms several other methods in designing channel simulators with desired distribution and correlation properties. We also show that the proposed method provides a subtle balance between channel model’s simplicity and accuracy in designing Rayleigh and Rice channel simulators. The parametrization is a process of determining the key parameters specifying the channel model. This process has a great influence on the reliability of the developed channel model. It is therefore highly desirable if those parameters are extracted from measurements. In fact, this idea constitutes the fundamental concept behind measurement-based channel modelling approach. The measurement-based models are important in the sense that they can be used for the optimizations of the wireless communication system. Hence, the problem of computing the channel model parameters from the measurements is of special interest. In this regard, we propose iterative nonlinear least square approximation method for the design of measurementbased channel simulators. Through detailed investigations and comparative studies, we demonstrate that the proposed method is highly flexible and outperforms several other conventional methods in terms of reproducing the correlation characteristics obtained from several measurements. In addition, we introduce a new approach for the design of channel models for V2X communications in tunnel environments, where the number of scatterers contributing to the total received power is relatively small

Development of a MATLAB Toolbox for Mobile Radio Channel Simulators

A profound knowledge of mobile radio channels is required for the development, evaluation, and also assessment at practical conditions of present and future mobile radio communication systems. The modelling, analysis, and simulation of mobile radio channels are important sub area since the initiation of mobile communications. In addition to that knowledge of channel behaviour in mobile radio communication is extensively recommended for the study of transmitter/receiver performances. Our intention in this master's thesis is to develop various kinds of mobile fading channel simulators using MATLAB and embed them into MATLB software as a toolbox. Implemented channel simulators were combined into a user-friendly Matlab toolbox from which users can easily select well-known channel models to test and to study the performance of mobile communication systems. The help file was developed based on HTML. It gives better support for the new users to work on the developed channel simulators, run the test procedures as well as parameter computation. The help file consistent with other supplementary programs like computation of PDF and CDF for different distributions, Rice simulation model, extended Suzuki process type I and II simulator etc. In addition to that each program consists with guidelines embedded with the source code. The help file web interfaces are listed in Appendix- 1.The toolbox can be integrated into the new release of Matlab software. The toolbox contains channel simulators for simulating non-stationary land mobile satellite channel, spatial shadowing processes, MIMO channels, multiple uncorrelated Rayleigh fading channels, mobile to mobile channel, frequency hopping channels etc. We developed set of test procedures, such as the autocorrelation function ACF, average duration of fades ADF, the probability density function PDF, and the level-crossing rate LCR etc., in order to test and to confirm the correctness of the implemented channel simulators. Proposed new algorithms to compute the model parameters of the channel simulators were also implemented in the toolbox to enable the parameterization of the channel simulators under specific propagation conditions. Finally, “how can a channel simulator be tested?” have been address in the thesis as a research question. It was based on the comparison of simulation results with the measured model or the reference model under different scenarios. In addition to that selection of the simulation time duration, sampling rate and size of the samples were considered. Developed test procedures were helped to assess the implemented channel simulators

Filter-Based Fading Channel Modeling

A channel simulator is an essential component in the development and accurate performance evaluation of wireless systems. A key technique for producing statistically accurate fading variates is to shape the flat spectrum of Gaussian variates using digital filters. This paper addresses various challenges when designing real and complex spectrum shaping filters with quantized coefficients for efficient realization of both isotropic and nonisotropic fading channels. An iterative algorithm for designing stable complex infinite impulse response (IIR) filters with fixed-point coefficients is presented. The performance of the proposed filter design algorithm is verified with 16-bit fixed-point simulations of two example fading filters

Statistical analysis of the capacity of mobile radio channels

Doktorgradsavhandling i informasjons- og kommunikasjonsteknologi, Universitetet i Agder, Grimstad, 201

Modelling, Analysis, and Simulation of Underwater Acoustic Channels : Doctoral Dissertation for the Degree Philosophiae Doctor (PhD) at the Faculty of Engineering and Science, Specialization in Information and Communication Technology

publishedVersio

Empirical multi-band characterization of propagation with modelling aspects for communictions

Diese Arbeit präsentiert eine empirische Untersuchung der Wellenausbreitung für drahtlose Kommunikation im Millimeterwellen- und sub-THz-Band, wobei als Referenz das bereits bekannte und untersuchte sub-6-GHz-Band verwendet wird. Die großen verfügbaren Bandbreiten in diesen hohen Frequenzbändern erlauben die Verwendung hoher instantaner Bandbreiten zur Erfüllung der wesentlichen Anforderungen zukünftiger Mobilfunktechnologien (5G, “5G and beyond” und 6G). Aufgrund zunehmender Pfad- und Eindringverluste bei zunehmender Trägerfrequenz ist die resultierende Abdeckung dabei jedoch stark reduziert. Die entstehenden Pfadverluste können durch die Verwendung hochdirektiver Funkschnittstellen kompensiert werden, wodurch die resultierende Auflösung im Winkelbereich erhöht wird und die Notwendigkeit einer räumlichen Kenntnis der Systeme mit sich bringt: Woher kommt das Signal? Darüber hinaus erhöhen größere Anwendungsbandbreiten die Auflösung im Zeitbereich, reduzieren das small-scale Fading und ermöglichen die Untersuchung innerhalb von Clustern von Mehrwegekomponenten. Daraus ergibt sich für Kommunikationssysteme ein vorhersagbareres Bild im Winkel-, Zeit- und Polarisationsbereich, welches Eigenschaften sind, die in Kanalmodellen für diese Frequenzen widergespiegelt werden müssen. Aus diesem Grund wurde in der vorliegenden Arbeit eine umfassende Charakterisierung der Wellenausbreitung durch simultane Multibandmessungen in den sub-6 GHz-, Millimeterwellen- und sub-THz-Bändern vorgestellt. Zu Beginn wurde die Eignung des simultanen Multiband-Messverfahrens zur Charakterisierung der Ausbreitung von Grenzwert-Leistungsprofilen und large-scale Parametern bewertet. Anschließend wurden wichtige Wellenausbreitungsaspekte für die Ein- und Multibandkanalmodellierung innerhalb mehrerer Säulen der 5G-Technologie identifiziert und Erweiterungen zu verbreiteten räumlichen Kanalmodellen eingeführt und bewertet, welche die oben genannten Systemaspekte abdecken.This thesis presents an empirical characterization of propagation for wireless communications at mm-waves and sub-THz, taking as a reference the already well known and studied sub-6 GHz band. The large blocks of free spectrum available at these high frequency bands makes them particularly suitable to provide the necessary instantaneous bandwidths to meet the requirements of future wireless technologies (5G, 5G and beyond, and 6G). However, isotropic path-loss and penetration-loss are larger with increasing carrier frequency, hence, coverage is severely reduced. Path-loss can be compensated with the utilization of highly directive radio-interfaces, which increases the resolution in the angular domain. Nonetheless, this emphasizes the need of spatial awareness of systems, making more relevant the question “where does the signal come from?” In addition, larger application bandwidths increase the resolution in the time domain, reducing small-scale fading and allowing to observe inside of clusters of multi-path components (MPCs). Consequently, communication systems have a more deterministic picture of the environment in the angular, time, and polarization domain, characteristics that need to be reflected in channel models for these frequencies. Therefore, in the present work we introduce an extensive characterization of propagation by intensive simultaneous multi-band measurements in the sub-6 GHz, mm-waves, and sub-THz bands. Firstly, the suitability of the simultaneous multi-band measurement procedure to characterize propagation from marginal power profiles and large-scale parameters (LSPs) has been evaluated. Then, key propagation aspects for single and multi-band channel modelling in several verticals of 5G have been identified, and extensions to popular spatial channel models (SCMs) covering the aforementioned system aspects have been introduced and evaluated

Massive MIMO channel models for 5G wireless communication systems and beyond

The recently standardised 5th generation (5G) wireless communication technologies and their evolution towards the 6th generation (6G) will enable low-latency, highdensity, and high-capacity communications across a wide variety of scenarios under tight constraints on energy consumption and limited availability of radio electromagnetic spectrum. Massive multiple-input multiple-output (MIMO) technologies will be key to achieve some of these goals and cover the ever-growing demand of data rates, reliability and seamless connectivity. Nowadays, the design and evaluation of new wireless communication technologies heavily rely on computationally-efficient channel models that can accurately capture essential propagation phenomena and flexibly adapt to a wide variety of scenarios. Thus, this thesis aims at providing methods of analysis of massive MIMO channels and developing advanced massive MIMO channel models that will help assess the 5G wireless communication technologies and beyond. First, key aspects of massive MIMO channels are investigated through a stochastic transformation method capable of modelling the space-time varying (STV) distribution of the delay and angle of arrival (AoA) of multi-path components (MPCs). The proposed method is followed by a channel modelling approach based on STV parameters of the AoA distribution that leads to closed-form expressions of key massive MIMO channel statistical properties. These methods are employed to analyse widelyused channel models and reveal some of their limitations. This investigation provides fundamental insights about non-stationary properties of massive MIMO channels and paves the way for developing subsequent efficient and accurate channel models. Second, three-dimensional (3D) non-stationary wideband geometry-based stochastic models (GBSMs) for massive MIMO communication systems are proposed. These models incorporate a novel approach to capture near-field effects, namely, the parabolic wavefront, that presents a good accuracy-complexity trade-off when compared to other existing techniques. In addition to cluster of MPCs (re)appearance, a Log-normal cluster-level shadowing process complements the modelling of large-scale fading over the array. Statistical properties of the models are derived and validated through simulations and measurements extracted from the available literature. Third, a highly-flexible and efficient 3D space-time non-stationary wideband massive MIMO channel model based on an ray-level evolution approach is proposed as a candidate for the design and assessment of 5G and beyond 5G (B5G) massive MIMO wireless communication technologies. The model can capture near-field effects, (dis)appearance, and large-scale fading of both clusters and individual MPCs by employing a single approach. Its efficiency relies upon a more realistic wavefront selection criterion, namely, the effective Rayleigh distance, which accounts for the limited lifespan of MPCs over the array. This novel criterion can help improve the efficiency of both existing and B5G massive MIMO channel models by greatly reducing the need for spherical wavefronts