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In this paper, novel ergodic capacity (EC) performance evaluation results of a power beacon (PB)-assisted multi-input multi-output (MIMO) wireless powered communication network are presented. In the considered system, the energy harvesting node harvests energy from the radio-frequency signals sent by the dedicated PB and uses this energy to communicate with the destination node. To accurately model the combined effect of multi-path fading and shadowing, it is assumed that the energy transfer link is subject to $\kappa$ - $\mu$ shadowed fading. Performance evaluation results are presented for two cases, depending upon the availability of channel state information (CSI) at the PB, namely, $no$ CSI and $full$ CSI. In the former case, equal power allocation is assumed, whereas, in the later case, energy beamforming is employed to increase energy transfer efficiency. For the performance evaluation of EC under $full$ CSI, a closed-form approximation for the probability density function of the maximum eigenvalue of a $\kappa$ - $\mu$ shadowed distributed random matrix is derived. For both $no$ CSI and $full$ CSI cases, lower and upper bounds on the achievable EC are derived in closed-form. Moreover, in order to obtain further insights on the impact of key parameters on the system performance, asymptotic EC expressions which become very tight at low- and high-signal-to-noise ratio regimes, are obtained. Using the proposed EC lower bound as well as these asymptotic results, simple closed-form expressions for the optimal time split that maximize the achievable EC are derived. Numerically evaluated results accompanied with Monte-Carlo simulations are further presented to corroborate the theoretical analysis. [ABSTRACT FROM AUTHOR]

In this letter, we study the performance of wireless communications empowered by Reconfigurable Intelligent Surface (RISs) over Nakagami- $m$ fading channels. We consider two phase configuration designs for the RIS, one random and another one based on coherent phase shifting. For both phase configuration cases, we present single-integral expressions for the outage probability and the bit error rate of binary modulation schemes, which can be efficiently evaluated numerically. In addition, we propose accurate closed-form approximations for the ergodic capacity of the considered system. For all considered metrics, we have also derived simple analytical expressions that become tight for large numbers of RIS reflecting elements. Numerically evaluated results compared with Monte Carlo simulations are presented in order to verify the correctness of the proposed analysis and showcase the impact of various system settings. [ABSTRACT FROM AUTHOR]

In this paper, we present a comprehensive framework for the performance analysis of dual-hop relaying communications with variable gain amplify-and-forward (AF) relays and operating in the presence of both multipath fading and shadowing, modeled by the Fisher-Snedecor $\mathcal {F}$ -distribution. Novel closed-form expressions for the probability density function (PDF) and the cumulative distribution function (CDF) of the end-to-end signal-to-noise ratio (SNR) of the considered system subject to hardware impairments are first derived. Single-integral expressions for the numerical evaluation of the $n$ -th moment of the end-to-end SNR, the outage probability (OP), the ergodic capacity under different adaptive transmission schemes, the effective capacity and the average bit error rate (ABER) of $M$ -ary modulation schemes are further presented. The proposed analytical expressions are valid for most of the well-known fading distributions, provided that the moment generating function (MGF) of the inverse SNR of each hop is readily available. For the special case of ideal hardware, it is shown that the above performance metrics can be expressed in closed-form. It is worth pointing out that the proposed analysis is valid even when the destination node is equipped with multiple antennas and maximal ratio combining (MRC) is employed. The correctness of the proposed mathematical analysis is validated through extensive numerically evaluated results accompanied with Monte-Carlo simulations. [ABSTRACT FROM AUTHOR]

This paper presents novel moment generating function (MGF)- and characteristic function (CHF)-based frameworks for the EC performance analysis of a generic $L_{p}$ -norm diversity combining scheme under adaptive transmission policies. The considered system operates over generalized fading channels, a maximum delay constraint and under various channel state information (CSI) conditions. Depending upon the operational CSI, four policies are studied, namely: i) Constant power with optimal rate adaptation (ORA); ii) Optimal power and rate adaptation (OPRA); iii) Channel inversion with fixed rate (CIFR); and iv) Truncated CIFR (TIFR). The $L_{p}$ -norm diversity is a generic diversity structure which includes as special cases various well-known diversity schemes, such as equal gain combining (EGC), maximal ratio combining (MRC) and amplify-and-forward (AF) relaying. Under the ORA and OPRA policies, we derive single integral expressions for evaluating the EC of $L_{p}$ -norm diversity reception directly from the MGF or the incomplete MGF of the Signal-to-Noise-Ratio (SNR) at the receiver, respectively. For the EC performance evaluation of the EGC and AF relaying systems operating under the OPRA policy, a CHF-based approach, which is computationally more efficient as compared to the MGF-based approach, is further presented. It is shown that the EC for the CIFR and TIFR policies can be directly evaluated from the MGF or the CHF of the SNR at the receiver, respectively. For the ORA policy, a novel analytical approach for the asymptotic EC performance analysis is also developed and evaluated, revealing how important system operation parameters affect the overall system performance. The mathematical formalism is validated with selected numerical and equivalent simulation performance evaluation results, thus confirming the correctness of the proposed analytical methodology. [ABSTRACT FROM AUTHOR]

This letter presents novel analytical expressions for the ergodic capacity (EC) of dual-hop amplify-and-forward (AF) relaying systems subject to hardware impairments operating over generalized fading channels. Our expressions are quite generic, providing that the moment-generating function (MGF) of the signal-to-noise ratio (SNR) or the MGF of the inverse SNR of each hop is readily available. The proposed analytical framework is further applied to assess the EC performance of two system setups: 1) a variable-gain relaying system equipped with multiple antennas at the relay and at the destination, assuming an interference-limited relay and a noise-limited destination and 2) a multi-source multi-destination AF system equipped with variable- or fixed-gain relays. The correctness of the proposed mathematical analysis is verified by Monte Carlo simulations results. [ABSTRACT FROM AUTHOR]

We introduce a novel analytical framework for the end-to-end (e2e) maximum throughput under delay constraints, namely effective capacity (EC), for multisource and multidestination amplify-and-forward cooperative networks. The network operates in the presence of Rayleigh fading and employs frequency-division duplex nodes having the ability to simultaneously transmit as sources and receive as relays. Cochannel interference and noise are present at the relay nodes, whereas the destination nodes are noise limited. A linear precoding technique is applied during reception to combine the input signals. As precoding, zero forcing (ZF), maximal-ratio combining (MRC), and minimum mean-squared error (MMSE) are studied. Each relay forwards the received signal to the destination by employing the maximum-ratio transmission (MRT) scheme. Both exact analytical expressions and tight high signal-to-noise ratio bounds of e2e EC are obtained for the ZF/MRT scheme while the optimal power allocation problem maximizing the e2e EC is also addressed. For the MRC/MRT and MMSE/MRT schemes, we derive approximate, yet highly accurate EC analytical expressions, as well as asymptotically tight closed-form expressions. Selected numerical and simulation results show that MMSE/MRT always yields the best performance followed by the ZF/MRT and MRC/MRT schemes. Moreover, it is shown that as the number of relay nodes increases, the ZF/MRT and MMSE/MRT schemes achieve almost identical and always better e2e EC performance than the MRC/MRT one. [ABSTRACT FROM AUTHOR]

Ensuring the physical layer security (PHY-security) of millimeter-wave (mmWave) communications is one of the key factors for the success of 5G. Recent field measurements show that conventional fading models cannot accurately model the random fluctuations of mmWave signals. To tackle this challenge, the fluctuating two-ray (FTR) fading model has been proposed. In this correspondence, we comprehensively analyze the PHY-security in mmWave communications over FTR fading channels. More specifically, we derive analytical expressions for significant PHY-security metrics, such as the average secrecy capacity, the secrecy outage probability, and the probability of strictly positive secrecy capacity, with simple functions. The effect of channel parameters on the PHY-security has been validated by numerical results. [ABSTRACT FROM AUTHOR]

This letter presents novel results for the high-order capacity statistics of equal gain combining diversity receivers. The proposed methodology to obtain these results includes in the analysis the study of generalized fading channels and an arbitrary number of receiving antennas. Analytical expressions for the $n$ -th order capacity statistics as well as for the amount of dispersion, the reliability of the signal throughput, the kurtosis, and the skewness of the channel capacity distribution have been derived. The validity of the proposed methodology has been verified by means of Monte Carlo computer simulations. Furthermore, it has been shown that previously published results for the first-order capacity statistics are included in the analysis as special cases. [ABSTRACT FROM AUTHOR]

The frequency scarcity imposed by fast growing demand for mobile data service requires promising spectrum aggregation systems. The so-called higher order statistics (HOS) of the channel capacity is a suitable metric on the system performance. While prior relevant works have improved our knowledge on the HOS characterization of spectrum aggregation systems, an analytical framework encompassing generalized fading models of interest is not yet available. In this paper, we pursue a detailed HOS analysis of $\kappa $ - $\mu $ and $\kappa $ - $\mu $ shadowed fading channels by deriving novel and exact expressions. Furthermore, the simplified HOS expressions for the asymptotically low and high signal-to-noise regimes are derived. Several important statistical measures, such as amount of fading, amount of dispersion, reliability, skewness, and kurtosis, are obtained by using the HOS results. More importantly, the useful implications of system and fading parameters on spectrum aggregation systems are investigated for channel selection. Finally, all derived expressions are validated via Monte Carlo simulations. [ABSTRACT FROM PUBLISHER]

This paper presents a thorough performance analysis of dual-hop cognitive amplify-and-forward (AF) relaying networks under spectrum-sharing mechanism over independent nonidentically distributed (i.n.i.d.) \eta-\mu fading channels. In order to guarantee the quality of service (QoS) of primary networks, both the maximum tolerable peak interference power \mathcal{Q} at the primary users (PUs) and the maximum allowable transmit power \mathcal{P}$ at the secondary users (SUs) are considered to constrain transmit power at the cognitive transmitters. For integer-valued fading parameters, a closed-form lower bound for the outage probability (OP) of the considered networks is obtained. Moreover, assuming arbitrary-valued fading parameters, the lower bound in integral form for the OP is derived. In order to obtain further insights into the OP performance, asymptotic expressions for the OP at high SNRs are derived, from which the diversity/coding gains and the diversity–multiplexing gain tradeoff (DMT) of the secondary network can be readily deduced. It is shown that the diversity gain and the DMT are solely determined by the fading parameters of the secondary network, whereas the primary network only affects the coding gain. The derived results include several others available in previously published studies as special cases, such as those for Nakagami- $m$ fading channels. In addition, performance evaluation results have been obtained by Monte Carlo computer simulations, which have verified the accuracy of the theoretical analysis. [ABSTRACT FROM AUTHOR]

Secrecy capacity is a fundamental information-theoretic performance metric to predict the maximum data rate of reliable communication, while the intended message is not revealed to the eavesdropper. Motivated by this consideration in this paper, a unified communication-theoretic framework for the analysis of the probability of nonzero secrecy capacity, the secrecy outage probability, and the secrecy capacity of multiple-antenna systems over fading channels is proposed. Specifically, a powerful frequency-domain approach is first developed in which the integrals involved in the evaluation of the probability of nonzero secrecy capacity and secrecy outage probability are transformed into the frequency domain, by employing Parseval’s theorem. A generic approach for the evaluation of the asymptotic secrecy outage probability at high signal-to-noise ratio (SNR) region is also introduced, thus providing useful insight as to the parameters affecting the secrecy performance. Finally, a unified numerical approach for computing the average secrecy capacity of multiple-antenna systems under arbitrary fading environments is developed. The proposed framework is general enough to accommodate any well-known multiantenna transmission technique and fading model. Finally, the secrecy performance of several multiple-antenna system setups is assessed, in the presence of generalized fading conditions and arbitrary antenna correlation, while various numerical and computer simulation results are shown and compared to substantiate the proposed mathematical analysis. [ABSTRACT FROM AUTHOR]

This paper elaborates on the end-to-end capacity of dual-hop free-space optical (FSO) communication systems employing amplify-and-forward (AF) relaying, assuming channel state information is only known at the receiving terminals. The relay is assumed to either possess perfect channel state information or have a fixed gain. The performance of the considered system is affected by the combined effects of atmospheric turbulence-induced fading, pointing errors (i.e., misalignment fading), and path loss. Atmospheric turbulence conditions are modeled using the gamma-gamma distribution. For the system under consideration, accurate analytical approximations as well as upper bounds to the ergodic capacity are derived. In addition, bound approximations in the high signal-to-noise ratio regime are deduced that provide valuable insights into the impact of model parameters on the capacity of AF FSO dual-hop relaying systems. Numerically evaluated and computer simulation results are further provided to demonstrate the validity of the proposed mathematical analysis. [ABSTRACT FROM PUBLISHER]

In this paper, a generalized Laguerre polynomial expansion for the probability density function and the cumulative distribution function of the sum of independent nonidentically distributed squared \kappa - \mu random variables is proposed. Based on these statistical results, we investigate the performance of maximal-ratio-combining diversity techniques operating over \kappa - \mu fading channels with arbitrary fading parameters. Our newly derived formulas are mathematically tractable and include as special cases several results available in the technical literature, namely, those of Rice and Nakagami-m fading channels. The proposed analysis is substantiated by numerically evaluated results compared with Monte Carlo simulations. [ABSTRACT FROM PUBLISHER]

In this paper, a study on the end-to-end performance of multihop free-space optical wireless systems over turbulence-induced fading channels, modeled by the gamma-gamma distribution, is presented. Our analysis is carried out for systems employing amplify-and-forward channel-state-information-assisted or fixed-gain relays. To assess the statistical properties of the end-to-end signal-to-noise ratio for both considered systems, we derive novel closed-form expressions for the moment-generating function, the probability density function, and the cumulative distribution function of the product of rational powers of statistically independent squared gamma-gamma random variables. These statistical results are then applied to studying the outage probability and the average bit error probability of binary modulation schemes. Also, for the case of channel-state-information-assisted relays, an accurate asymptotic performance analysis at high SNR values is presented. Numerical examples compare analytical and simulation results, verifying the correctness of the proposed mathematical analysis. [ABSTRACT FROM PUBLISHER]