The complex α-μ fading channel with OFDM application

The aims of this paper are threefold: (i) to present a model for the complex - fading channel; (ii) to propose an efficient, simple, and general method to generate complex - samples; (iii) to make use of this channel in order to assess the bit error rate performance of an OFDM system. An analytical framework is then used, whose output is validated through Monte Carlo simulation. Several important conclusions concerning the system performance as a function of the channel parameters, namely, nonlinearity, clustering, and power imbalance of in-phase and quadrature components, are drawn2017Recent advances in RF propagation modeling for 5G systemsFINANCIADORA DE ESTUDOS E PROJETOS - FINEP01.14.0231.0

ВЕРОЯТНОСТЬ ОШИБОК ПРИ ПРИЕМЕ СИГНАЛОВ ПО УПЛОТНЕННЫМ КАНАЛАМ СВЯЗИ С ОРТОГОНАЛЬНЫМ ЧАСТОТНЫМ РАЗДЕЛЕНИЕМ

A mathematical analysis of the probability of errors in the reception of signals transmitted over compressed communication channels with orthogonal frequency separation in the presence of fading in the communication channel distributed in accordance with the Nakagami-m distribution law is made. Unlike previous publications, the present work considers the effect of non-uniform distribution of the phase of fading in the communication channel on the probability of errors in signal reception. A unified mathematical expression of the generating function of the moments for fading of the communication channel in the frequency domain, distributed according to the Nakagami-m law, is presented for uneven fading phase distributions in the communication channel. Thus, the classical methods of determining the generating function of moments can be used directly to obtain exact mathematical expressions for the probability of signal reception errors for various types of modulation and signal diversity.Проводится математический анализ вероятности ошибок приема сигналов, передаваемых по уплотненным каналам связи с ортогональным частотным разделением при наличии замираний в канале связи, распределенных в соответствии с законом распределения Накагами- m . В отличие от предшествующих публикаций в настоящей работе рассматривается воздействие неравномерного распределения фазы замираний в канале связи на вероятность ошибок приема сигналов. Представлено унифицированное математическое выражение производящей функции моментов для замираний канала связи в частотной области, распределенных в соответствии с законом Накагами- m , при неравномерных распределениях фазы замираний в канале связи. Таким образом, классические методы определения производящей функции моментов могут непосредственно использоваться для получения точных математических выражений вероятности ошибок приема сигналов для различных видов модуляции и разнесения сигналов

Processing of orthogonal frequency-compensated signals transmitted via communication channels with fading

В работе проводится математический анализ вероятностных характеристик сигналов, передаваемых по уплотненным каналам связи с ортогональным частотным разделением при наличии замираний в канале связи, подчиняющихся закону распределения Накагами-m. В отличие от предыдущих исследований в настоящей работе рассматривается воздействие неоднородного распределения фазы замираний в канале связи на вероятность ошибок приема сигналов. Представлено унифицированное математическое выражение производящей функции моментов для коэффициентов замираний в канале связи в частотной области, распределенных в соответствии с законом Накагами-m с неоднородными распределениями фазы. Таким образом, классические методы определения производящей функции моментов могут непосредственно использоваться для определения точного математического представления вероятности ошибки приема сигналов при различных видах модуляции и разнесении сигналов. The mathematical analysis of the probabilistic characteristics of signals transmitted through compressed communication channels with orthogonal frequency separation in the presence of fading in the communication channel obeying the Nakagami-m distribution law is carried out in the paper. In contrast to previous studies, the effect of a non-uniform distribution of the fading phase in a communication channel on the probability of signal reception errors is examined. A unified mathematical expression of the generating function of moments is presented for the fading coefficients in the communication channel in the frequency domain, distributed in accordance with the Nakagami-m law with non-uniform phase distributions. Thus, the classical methods for determining the generating function of moments can be directly used to determine the exact mathematical representation of the probability of error receiving signals for various types of modulation and diversity of signals

ОБРАБОТКА ОРТОГОНАЛЬНЫХ ЧАСТОТНО-УПЛОТНЕННЫХ СИГНАЛОВ, ПЕРЕДАВАЕМЫХ ПО КАНАЛАМ СВЯЗИ С ЗАМИРАНИЯМИ

The mathematical analysis of the probabilistic characteristics of signals transmitted through compressed communication channels with orthogonal frequency separation in the presence of fading in the communication channel obeying the Nakagami-m distribution law is carried out in the paper. In contrast to previous studies, the effect of a non-uniform distribution of the fading phase in a communication channel on the probability of signal reception errors is examined. A unified mathematical expression of the generating function of moments is presented for the fading coefficients in the communication channel in the frequency domain, distributed in accordance with the Nakagami-m law with non-uniform phase distributions. Thus, the classical methods for determining the generating function of moments can be directly used to determine the exact mathematical representation of the probability of error receiving signals for various types of modulation and diversity of signals.В работе проводится математический анализ вероятностных характеристик сигналов, передаваемых по уплотненным каналам связи с ортогональным частотным разделением при наличии замираний в канале связи, подчиняющихся закону распределения Накагами-m. В отличие от предыдущих исследований в настоящей работе рассматривается воздействие неоднородного распределения фазы замираний в канале связи на вероятность ошибок приема сигналов. Представлено унифицированное математическое выражение производящей функции моментов для коэффициентов замираний в канале связи в частотной области, распределенных в соответствии с законом Накагами-m с неоднородными распределениями фазы. Таким образом, классические методы определения производящей функции моментов могут непосредственно использоваться для определения точного математического представления вероятности ошибки приема сигналов при различных видах модуляции и разнесении сигналов

Cooperative underwater acoustic communications

This article presents a contemporary overview of underwater acoustic communication (UWAC) and investigates physical layer aspects on cooperative transmission techniques for future UWAC systems. Taking advantage of the broadcast nature of wireless transmission, cooperative communication realizes spatial diversity advantages in a distributed manner. The current literature on cooperative communication focuses on terrestrial wireless systems at radio frequencies with sporadic results on cooperative UWAC. In this article, we summarize initial results on cooperative UWAC and investigate the performance of a multicarrier cooperative UWAC considering the inherent unique characteristics of the underwater channel. Our simulation results demonstrate the superiority of cooperative UWAC systems over their point-to-point counterparts. © 1979-2012 IEEE

Approximations for the inverse cumulative distribution function of the gamma distribution used in wireless communication

The use of quantile functions of probability distributions whose cumulative distribution is intractable is often limited in Monte Carlo simulation, modeling, and random number generation. Gamma distribution is one of such distributions, and that has placed limitations on the use of gamma distribution in modeling fading channels and systems described by the gamma distribution. This is due to the inability to find a suitable closed-form expression for the inverse cumulative distribution function, commonly known as the quantile function (QF). This paper adopted the Quantile mechanics approach to transform the probability density function of the gamma distribution to second-order nonlinear ordinary differential equations (ODEs) whose solution leads to quantile approximation. Closed-form expressions, although complex of the QF, were obtained from the solution of the ODEs for degrees of freedom from one to five. The cases where the degree of freedom is not an integer were obtained, which yielded values closed to the R software values via Monte Carlo simulation. This paper provides an alternative for simulating gamma random variables when the degree of freedom is not an integer. The results obtained are fast, computationally efficient and compare favorably with the machine (R software) values using absolute error and Kullback–Leibler divergence as performance metrics

Broadband wireless communication systems: Channel modeling and system performance analysis

Wideband channel modeling, which can accurately describe the most important characteristics of wideband mobile fading channels, is essential for the design, evaluation, and optimization of broadband wireless communication systems. In the field of wideband channel modeling, the tradeoff between the prediction accuracy and simulation efficiency has to be taken into account. On one hand, channel models should be as accurate as possible. On the other hand, channel models are supposed to be simple and easy to put into use. There are several commonly used approaches to channel modeling, e.g., measurement-based channel modeling and deterministic channel modeling. Both methods are efficient in capturing the fading behavior of real-world wireless channels. However, the resulting channel models are only valid for the specific environments as those where the measurements were carried out or the ray-tracing scenario was considered. Moreover, these methods are quite time consuming with high computational cost. Alternatively, the geometry-based stochastic channel modeling approach can be employed to model wideband mobile fading channels. The most attractive feature of this method is that the derived channel models are able to predict fading behavior for various propagation environments, and meanwhile they can be easily implemented. Thus, the dissertation will complete the wideband channel modeling task by adopt the geometry-based stochastic approach. In the dissertation, several geometry-based channel models are proposed for both outdoor and indoor propagation scenarios. The significance of the work lies in the fact that it develops channel models under more realistic propagation conditions which have seldom been considered, such as for non-isotropic scattering environxi ments and mobile-to-mobile (M2M) fading channels. In addition, the proposed channel models remove the scarcity that proper geometry-based channel models are missing for indoor environments. The most important statistical properties of the developed channel models including their temporal autocorrelation function (ACF), the two-dimensional (2D) space cross-correlation function (CCF), and the frequency correlation function (FCF) are analyzed. Furthermore, efficient channel simulators with low realization expenditure are obtained. Finally, the validity of the proposed channel models is demonstrated by comparing their analytical channel statistics with the empirical ones measured from real world channels. Besides the work in the field of wideband channel modeling, another part of the dissertation is dedicated to investigate the performance of SISO1 orthogonal frequency division multiplexing (OFDM) broadband communication systems and space-time (ST) coded MIMO2 OFDM broadband communication systems. This work provides a deep insight into the performance of a broadband mobile radio communication system over realistic wideband fading channels. Analytical expressions are derived for bit error probability (BEP) or symbol error rate (SER) of systems. In order to confirm the correctness of the theoretical results as well as to show the usefulness of the wideband channel models in the testing and analysis of a broadband communication system, SISO OFDM systems and space-time coded MIMO OFDM systems are simulated in the dissertation. In order to improve the reliability of digital transmission over broadband wireless radio channels, a differential super-orthogonal space-time trellis code (SOSTTC) is designed for noncoherent communications, where neither the transmitter nor the receiver needs the channel state information (CSI) for decoding. In addition, a new decoding algorithm is proposed. The new algorithm has exactly the same decoding performance as the traditional one. However, it is superior from the standpoint of overall computing complexity

Communications over fading channels with partial channel information : performance and design criteria

The effects of system parameters upon the performance are quantified under the assumption that some statistical information of the wireless fading channels is available. These results are useful in determining the optimal design of system parameters. Suboptimal receivers are designed for systems that are constrained in terms of implementation complexity. The achievable rates are investigated for a wireless communication system when neither the transmitter nor the receiver has prior knowledge of the channel state information (CSI). Quantitative results are provided for independent and identically distributed (i.i.d.) Gaussian signals. A simple, low-duty-cycle signaling scheme is proposed to improve the information rates for low signal-to-noise ratio (SNR), and the optimal duty cycle is expressed as a function of the fading rate and SNR. It is demonstrated that the resource allocations and duty cycles developed for Gaussian signals can also be applied to systems using other signaling formats. The average SNR and outage probabilities are examined for amplify-and-forward cooperative relaying schemes in Rayleigh fading channels. Simple power allocation strategies are determined by using knowledge of the mean strengths of the channels. Suboptimal algorithms are proposed for cases that optimal receivers are difficult to implement. For systems with multiple transmit antennas, an iterative method is used to avoid the inversion of a data-dependent matrix in decision-directed channel estimation. When CSI is not available, two noncoherent detection algorithms are formulated based on the generalized likelihood ratio test (GLRT). Numerical results are presented to demonstrate the use of GLRT-based detectors in systems with cooperative diversity