Search

The need for the distribution of combination of random variables (RVs) arises in many areas of sciences and engineering. In this paper, closed-form approximations for the distribution of squared sum of products of independent Nakagami-m RVs are derived. Three different approaches (central limit theorem, Edgeworth expansion, and a one-term gamma approximation) are considered. The Kolmogorov-Smirnov, Anderson-Darling, and Cramer-von Mises statistics are used as a quantitative metrics to compare the derived distribution forms with the empirical distribution obtained from a simulation study. Furthermore, an application for the derived distributions in wireless communication field is presented. As a result, it is shown that the most accurate and simplest closed-form expression is the one obtained by a one-term gamma approximation. [ABSTRACT FROM AUTHOR]

In this paper, the performance of the dual-hop radio frequency/free space optical (RF/FSO) system based on the amplify-and-forward (AF) and decode-and-forward (DF) relaying schemes is analyzed. The RF link is modeled by Nakagami-m distribution for the multipath fading channel which is a generalized distribution. The FSO link is characterized by Fisher-Snedecor (F ) fading distribution that is valid for all atmospheric turbulence conditions. Operating the intensity modulation direct detection scheme, the unified expression of the cumulative distribution function (CDF) is employed for the instantaneous end-to-end received signal-to-noise ratio (SNR). By utilizing its CDF, a novel mathematical framework to drive the exact closed-form expressions of the outage probability (OP) and the average bit error rate (ABER) with different modulation schemes are calculated for the considered system involving Meijer-G functions. Additionally, to get a deeper understanding, asymptotic expressions for the OP and ABER are also obtained in terms of basic elementary functions. Further, the analytical results collaborate with simulation results which validate the use of the derived expressions. The results revealed that increases in the severity of atmospheric turbulence profoundly degrade the system performance. Furthermore, comparisons between dual-hop RF/FSO systems, hybrid RF/FSO systems, and single FSO systems are presented. [ABSTRACT FROM AUTHOR]

Mobile communications systems are affected by what is known as fading, which is a well-known problem largely studied for decades. The direct consequence of fading is the complete loss of signal (or a large decrease of the received power). Rayleigh fading is a reasonable model for wireless channels although, Nakagami-m distribution seems better suited to fitting experimental data. In this paper we obtain the Nakagami-m distribution as a composite (mixture) of the Rayleigh distribution, a result which as far as we know it has not been shown in the literature. This representation of the Nakagami-m distribution facilitates computations of the average BER (Bit Error Rate) for DPSK (Differential Phase Shift Keying) and MSK (Minimum-Shift Keying) modulations for this distribution and higher moments of them, which is of great applicability to modeling wireless fading channels. Furthermore, a simple, not depending on any special function, apart of the Gamma function, bivariate version of the Nakagami-m distribution is also proposed as a special case of the multivariate version which is also presented. The proposed composite distribution is simulated through the standard procedure of summation of phasors, and results for the new closed-form measures for the MSK modulation are also shown. From that it is clear that the alternative formulation of the Nakagami-m distribution allows for easier modeling of fading fading-shadowing wireless channels through the new explicit second order statistics metrics. is well suited for modelling fading-shadowing wireless channels. [ABSTRACT FROM AUTHOR]

Nonorthogonal multiple access (NOMA) is used to superpose multifarious user signals for concurrent transmission, enhancing spectral efficiency. Additionally, wireless energy sources neighbouring the NOMA sender are utilized for enhanced energy efficiency. Practically, nonlinear energy harvesting (nlEH) circuits reflect faithfully characteristics of components implementing these circuits. In addition, reflected intelligent surface (RIS) is helpful with a role of the relay to maintain communication from the NOMA sender to the far NOMA recipient. However, challenges in RIS-aided NOMA with nlEH (RISaNOMAwEH) include channel state error (CSE) and fading severity. These factors directly impact harvested energy and communication reliability. As such, this paper analyzes their influences on the RISaNOMAwEH through three pivotal metrics (total throughput, outage probability, energy efficiency) under practical considerations like the nlEH, the CSE, and relatively-general fading (Nakagami-m). Demonstrative results reveal that the CSE, the fading severity m, and the quantity of the reflectors of the RIS drastically impact these metrics whereas the nlEH slightly influences them. Remarkably, the RISaNOMAwEH can conduct the prevention of complete outage through proper adoption of required spectral efficiency (R), time splitting factor (η) , and power splitting coefficient. Moreover, optimum metrics are achieved with the optimal configuration of parameters (R , η) . Furthermore, the proposed scheme dramatically outperforms a benchmark scheme (RIS-aided orthogonal multiple access (OMA) with nlEH) in various parameter configurations, highlighting the benefits of NOMA over OMA. [ABSTRACT FROM AUTHOR]

A reconfigurable intelligent surface (RIS)-aided wireless communication system is considered in this paper, where the transmitter sends data to the receiver via a direct link and the RIS. The phases of the reflecting elements of the RIS are selected considering the phases of all the fading channels to maximize the performance of the system. Series-form expressions for the probability density function (p.d.f.) and cumulative distribution function (c.d.f.) are derived for the composite channel of the communication system by considering the RIS channels to follow independent Nakagami-m distributions and the envelope of the direct channel to follow a Rayleigh distribution. Furthermore, the expressions for the statistics of the composite channel in terms of its p.d.f. and c.d.f. are also derived by considering the approximation of the central limit theorem (CLT) and the square of the channel envelope without the direct channel to approximately follow a Gamma distribution. Utilizing the derived statistics, the performance of the RIS-assisted system is studied by deriving series-form expressions for the symbol error probability (SEP) and outage probability. Numerical results are presented to corroborate the analytical framework. It is observed that a decreasing number of reflecting elements of the RIS and an increasing shape parameter of the fading channels increase the randomness of the overall channel of the RIS-assisted wireless system. Moreover, the inefficacy of both the approximate statistics is demonstrated via simulation studies of the p.d.f., c.d.f., SEP, and outage probability.

This paper presents exact formulas for the probability distribution function (PDF) and moment generating function (MGF) of the sum-product of statistically independent but not necessarily identically distributed (i.n.i.d.) Nakagami-m random variables (RVs) in terms of Meijer’s G-function. Additionally, exact series representations are also derived for the sum of double-Nakagami RVs, providing useful insights on the trade-off between accuracy and computational cost. Simple asymptotic analytical expressions are provided to gain further insight into the derived formula, and the achievable diversity order is obtained. The suggested statistical properties are proved to be a highly useful tool for modeling parallel cascaded Nakagami-m fading channels. The application of these new results is illustrated by deriving exact expressions and simple tight upper bounds for the outage probability (OP) and average symbol error rate (ASER) of several binary and multilevel modulation signals in intelligent reflecting surfaces (IRSs)-assisted communication systems operating over Nakagami-m fading channels. It is demonstrated that the new asymptotic expression is highly accurate and can be extended to encompass a wider range of scenarios. To validate the theoretical frameworks and formulations, Monte-Carlo simulation results are presented. Additionally, supplementary simulations are provided to compare the derived results with two common types of approximations available in the literature, namely the central limit theorem (CLT) and gamma distribution.

The advent of the next generation of wireless communication (NextGen) demands substantial investments and collaborative research for the fundamental need of wireless communications. Therefore, cooperative communication plays a vital role in overcoming challenges such as reliability, throughput, and outage trade-offs. We propose a two-transmission phase spectrum-sharing protocol, employing cooperative decode-and-forward relaying to grant spectrum access for both primary and secondary users. The system consists of a primary sender (PS), primary recipient (PR), secondary sender (SS), and secondary recipient (SR), linked as PS-SS, PS-PR, PS-SR, SS-SR, and SS-PR. In the first transmission phase, PS broadcasts the primary signal, received by PR, SS, and SR. SS regenerates the primary signal after successful reception, combining it linearly with the secondary signal, and allocating power fractions $\epsilon $ and ( $1 - \epsilon $ ) to the primary and secondary signals. SS then broadcasts the combined signal in the second transmission phase. Analysis reveals a threshold for optimal performance when SS is within range of PS. Beyond this threshold, the outage performance for the primary user equals or exceeds the case without spectrum sharing. The outage performance for the secondary system is also quantified. The performance of both the primary and secondary users is assessed by deriving a closed-form expression for the outage probability using the Nakagami-m distribution. The effectiveness of the scheme is affirmed through analytical and simulation results.

Reconfigurable intelligent surfaces (RISs) are acknowledged as one of the key technologies for the next-generation communication systems due to their low cost, high-energy efficiency, and the ability to intelligently control the wireless propagation environment. In this paper, we present a hybrid active–passive reconfigurable intelligent surface (HAPR) for cooperative transmission system, where HAPR can intelligently change its operating mode according to the channel environment, eliminating the "multiplicative fading" effect of traditional passive RIS (P-RIS) and higher power consumption of active RIS (A-RIS), and combining the advantages of both to effectively improve the system performance. First, we investigate the ideal reflection coefficient of RIS reflecting elements (REs) under the condition of a limited power budget. Using the compound Simpson formula, the closed-form approximation expression for the system outage probability (OP) has been derived. Finally, Monte Carlo simulation is used to confirm the accuracy of the expression. The simulation results demonstrate that HAPR has a better performance than both A-RIS and P-RIS, which can achieve a lower OP. [ABSTRACT FROM AUTHOR]

This paper investigates the impact of non-ideal environmental factors, including hardware impairments, random user distributions, and imperfect channel conditions, on the performance of distributed reconfigurable intelligent surface (RIS)-assisted air–ground fusion networks. Using an unmanned aerial vehicle (UAV) as an aerial base station, performance metrics such as the outage probability, ergodic rate, and energy efficiency are analyzed with Nakagami-m fading channels. To highlight the superiority of RIS-assisted air–ground networks, comparisons are made with point-to-point links, amplify-and-forward (AF) relay scenarios, conventional centralized RIS deployment, and fusion networks without hardware impairments. Monte Carlo simulations are employed to validate theoretical analyses, demonstrating that in non-ideal environmental conditions, distributed RIS-assisted air–ground fusion networks outperform benchmark scenarios. This model offers some insights into the improvement of wireless communication networks in emerging smart cities.

Reconfigurable intelligent surfaces (RISs) are acknowledged as one of the key technologies for the next-generation communication systems due to their low cost, high-energy efficiency, and the ability to intelligently control the wireless propagation environment. In this paper, we present a hybrid active–passive reconfigurable intelligent surface (HAPR) for cooperative transmission system, where HAPR can intelligently change its operating mode according to the channel environment, eliminating the “multiplicative fading” effect of traditional passive RIS (P-RIS) and higher power consumption of active RIS (A-RIS), and combining the advantages of both to effectively improve the system performance. First, we investigate the ideal reflection coefficient of RIS reflecting elements (REs) under the condition of a limited power budget. Using the compound Simpson formula, the closed-form approximation expression for the system outage probability (OP) has been derived. Finally, Monte Carlo simulation is used to confirm the accuracy of the expression. The simulation results demonstrate that HAPR has a better performance than both A-RIS and P-RIS, which can achieve a lower OP.

Unnamed aerial vehicles (UAVs) are of great importance on various platforms because of its rapid and easy deployment. In order to get an insight of UAV aided communication systems, an accurate channel model of UAV channels is needed. We propose a general channel model for UAV link based on alpha-beta model, which is extensively used in the literature. Specifically, we derive the normalized expression of probability density function (PDF), cumulative distribution function (CDF), and moments of the proposed model. Shadowing component is assumed to follow log-normal distribution and multipath component is characterized with the help of Nakagami-m distribution. The outage probability of a UAV based communication system is also obtained by using CDF expression. [ABSTRACT FROM AUTHOR]

Underlay device-to-device (D2D) communication network is becoming a promising solution for the fifth generation (5G) and beyond wireless technology. It exploits the proximity of the D2D pairs and improves the overall network’s latency, capacity, and spectral efficiency by sharing/reusing the existing cellular resources. However, due to the frequency-sharing/reusing, the security of the device users (DUs) and the cellular users (CUs) becomes vulnerable. This paper presents a novel physical-layer security (PLS) scheme for the underlay multiple-input multiple-output (MIMO) D2D communications in the presence of multiple eavesdroppers. The proposed new PLS scheme can significantly reduce the information leakage for both CUs and DUs by adopting a null steering scheme at the transmitter. A signal alignment technique is also employed to eradicate the stringent requirement of a larger number of transmitter antennas than that of the receiver antennas. A generalized nonlinear optimization problem has been formulated to improve the PLS performance for MIMO-D2D communications. A closed-form and generalized analytical expression of the secrecy outage probability for CUs and DUs is derived over the imperfect Nakagami- $m$ and Norton fading channels. Theoretical and simulation results of our proposed new PLS scheme have shown significant improvement in the secrecy capacity and secrecy outage probability for both CUs and DUs in comparison with the existing methods. [ABSTRACT FROM AUTHOR]

An output signal from a multi-section wireless relay communication system is equal to the product of the signal envelopes from individual sections. In this paper, a three-sections relay system is considered in the presence of Nakagami-m fading at each section. First, random variable (RV) is formed as the product of three Nakagami-m RVs. For such product, the moments are determined in the closed forms. The first moment is the mean of the signal; the second moment is the average power of the signal, and the third moment is skewness. Then, the Amount of Fading (AoF) is calculated. AoF is a measure of the severity effect of fading in a particular channel model. Besides, all system performance are shown graphically and the parameters influence has been analyzed and discussed.

For outdoor millimeter-wave mobile radio systems, the main service area is expected to be in line-of-sight (LOS) and semi-line-of-sight (SLOS) environments. The modeling of propagation in a mixed LOS/SLOS environment is thus important in system design. For modeling propagation in an SLOS environment, the application of the Loo model developed for land mobile satellite service with roadside shadowing is promising because this model reflects the physical mechanism of radio propagation. However, the model is inconvenient in practice because its calculation involves numerical integration over an infinite range. In this article, we approximate the Loo distribution using three basic distributions, namely the Nakagami-Rice distribution (or Rician distribution), Nakagami-m distribution, and lognormal distribution. Based on the evaluation results, we propose the use of the Nakagami-m distribution in place of the Loo distribution. We demonstrate the conversion of Loo distribution parameters to Nakagami-m distribution parameters. Finally, we examine a multistate model that expresses environments composed of LOS, SLOS, and non-LOS conditions. [ABSTRACT FROM AUTHOR]

Under strong wind caused by a low pressure with fronts passing near Honshu, I have observed weather clutter containing targets (ships) using an X‐band marine radar with a frequency of 9.41 GHz, a beamwidth of 1.0°, a pulsewidth of 0.5 μs, and a pulse‐repetition frequency of 1600 Hz. To investigate such clutter amplitude statistics, I have introduced the Nakagami‐m distribution to radar signal processing for the first time and used the Akaike Information Criterion (AIC). It has been found that the weather clutter amplitudes obey the Nakagami‐m distribution with the shape parameter of m = 5.85 for entire data and the log‐normal, Weibull, log‐Weibull, and Nakagami‐m distributions with the shape parameters of σ = 0.189 to 0.259, c = 6.52 to 7.81, c = 26.66 to 35.51, and m = 5.23, respectively, for small data within the beam width of an antenna. The number of the minimum AIC (MAIC) of the log‐normal, Weibull, log‐Weibull, and Nakagami‐m distributions to data is 4, 12, 4, and 1, respectively, from 21 small data. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

In this paper, we discuss physical model based method to generate channel coefficients for Nakagami-m distribution. We consider the phase envelope joint distribution so that the phase of the faded signal is also considered. Mainly, the coefficients are generated by exploring the physical model that relates the Nakagami-m fading distribution with Gaussian and gamma distributions for which generation of coefficients is available in commonly used simulation tools. The empirical probability density function (PDF) of generated coefficients are compared with the theoretical values and they are found in excellent agreements. The empirical PDFs for envelope and phase of the generated coefficients are validated using the Kolmogorov–Smirnov test. [ABSTRACT FROM AUTHOR]

In this paper, the secrecy outage probability (SOP) of an energy harvesting aided underlay single input multiple output cognitive radio network under the multiple eavesdroppers is investigated. It is assumed that all the channels within the network are subjected to Nakagami‐m distributions. In order to quantify the secrecy performance of the concerned network, two eavesdroppers' scenarios are considered and this includes: Colluding Eavesdropping and noncolluding Eavesdropping. Based on these, the SOP closed‐form expressions are derived for the network under the two scenarios. Our findings illustrate that the network under the noncolluding eavesdropping scenario achieve better secrecy outage performance compared with colluding eavesdropping mode. Furthermore, the impact of number of eavesdroppers Ne, the number of antennas equipped at eavesdroppers Ae as well as fading parameter of the wiretap channel me on the network secrecy outage performance are demonstrated. Finally, the accuracy of the derived expressions is validated through the Monte‐Carlo simulations. [ABSTRACT FROM AUTHOR]

An output signal from a multi-section wireless relay communication system is equal to the product of the signal envelopes from individual sections. In this paper, a three-sections relay system is considered in the presence of Nakagami-m fading at each section. First, random variable (RV) is formed as the product of three Nakagami-m RVs. For such product, the moments are determined in the closed forms. The first moment is the mean of the signal; the second moment is the average power of the signal, and the third moment is skewness. Then, the Amount of Fading (AoF) is calculated. AoF is a measure of the severity effect of fading in a particular channel model. Besides, all system performance are shown graphically and the parameters influence has been analyzed and discussed. [ABSTRACT FROM AUTHOR]

Sums of fading envelopes occur in several wireless communications applications. The exact mathematical solution to this statistic is, however, rather intricate. In this paper, we derive a novel closedform approximation to the sum of not necessarily identically distributed Nakagami-m random variables. The necessary parameters of the approximate solution are estimated by using the well-known expectation maximization algorithm with a Nakagami-m mixture model. The proposed approximation finds applicability in obtaining important performance metrics of communications systems where sums of variates arise. More specifically, we apply the proposed method to derive a closed-form expression for average bit error probability (ABEP) of multibranch equal-gain combining receivers. The presented models are general and can be applied to any modulation scheme. Furthermore, simplified asymptotic closed-form expressions for the ABEP have been derived to examine the achievable diversity and coding gains. Finally, the performance of the proposed approach is verified by comparing itself against both the exact evaluation and the previous results in the literature.

Wireless communications and power line communications (PLC) are essential components for smart grid communications. This paper analyses the performance of a dual-hop wireless-power line mixed communication setup employing a decode-and-forward relay in terms of analytical average bit error rate (BER), outage probability, and average channel capacity. The Nakagami-m distribution captures the wireless channel fading; whereas the PLC channel gain is characterized by the Log-normal distribution. The additive PLC channel noise is assumed to be Bernoulli-Gaussian distributed. Approximate closed-form expression of the average BER and exact closed-form expression of the outage probability are derived for the considered system. Further, we obtain an approximate closed-form expression of the capacity of the wireless-power line mixed system in terms of the Meijer-G function. It is observed that the system performance deteriorates as the impulsive noise index and the arrival probability of the impulsive component of the PLC additive noise increase.

In this paper, we leverage concepts from stochastic geometry to investigate the downlink performance of a vertical heterogeneous network (VHetNet) comprising aerial base stations (ABSs) and terrestrial base stations (TBSs). We model the ABSs as a 2D Poisson point process (PPP) deployed at a particular altitude while the TBSs are modelled as a 2D PPP deployed on the ground. The proposed analytical framework adopts an appropriate air-to-ground (A2G) channel model that incorporates line-of-sight (LoS) and non-line-of-sight (NLoS) transmissions. We begin the main technical part of the analysis by deriving analytical expressions for the distribution of the distances between a typical user and the closest LoS ABS, NLoS ABS, and TBS. After that, we derive expressions for the probabilities that a typical user is associated with a NLoS ABS, LoS ABS, or TBS. Under the assumption that A2G and terrestrial channels experience Nakagami- $m$ fading with different $m$ parameters, we derive an expression for the Laplace transform of interference power. Furthermore, we derive exact and approximate analytical expressions for the coverage probability and achievable rate. We show that these approximations match the simulations with negligible errors for small SINR thresholds and $m$ parameters of Nakagami- $m$ fading. [ABSTRACT FROM AUTHOR]

The Nakagami-m distribution plays an important role in problems related to communication engineering. This distribution can also be used for modeling reliability data as its hazard rate (mean residual life) function presents increasing (decreasing) or bathtub (unimodal) shapes. In this study, a Bayesian inference considering objective priors for the Nakagami-m distribution parameters is presented. We propose a theorem with sufficient and necessary conditions so that a general class of posteriors are proper. The impropriety of these posteriors can be observed by the behavior of the objective priors. This theorem is applied to different objective priors such as Jeffreys’ rule, Jeffreys prior, maximal data information prior, and reference priors. Simulation studies were conducted to investigate the performance of the Bayes estimators. Finally, our methodology is illustrated using two real lifetime datasets showing that the Nakagami-m distribution can be used to describe lifetime data. [ABSTRACT FROM PUBLISHER]

The distributions of random variables are of interest in many areas of science. In this paper, ascertaining on the importance of multi-hop transmission in contemporary wireless communications systems operating over fading channels in the presence of cochannel interference, the probability density functions (PDFs) of minimum of arbitrary number of ratios of Rayleigh, Rician, Nakagami-m, Weibull and α-µ random variables are derived. These expressions can be used to study the outage probability as an important multi-hop system performance measure. Various numerical results complement the proposed mathematical analysis.

In this paper, performance analysis of diversity technique with equal gain combining method (EGC) with two branches for the detection of signals in wireless communication systems is presented. In the following analysis, it is assumed that the fading via channels is Nakagami-m correlated. The first order statistical characteristics of the system are analysed. Useful formulae for the probability density function (pdf) and cumulative distribution function (CDF) of EGC output SIR are derived, and the effects of the fading severity on the output signal are observed.

Power line communication (PLC) utilizes power lines for the purpose of electronic data transmission. Differential binary phase shift keying (DBPSK) is a popular modulation scheme proposed in the PLC standards like G3, PRIME, and IEEE P1901.2. This letter provides the performance evaluation of a PLC system assuming DBPSK modulation under the combined effect of Nakagami-$m$ background noise and impulsive noise. We utilize a simple, yet accurate approximation available in literature to derive the probability density function of the sum of two Nakagami-$m$ random variables. Closed-form expressions of the analytical average bit error rate and the outage probability of the system are derived. Validity of the derived analytical expressions is closely verified by simulated results. [ABSTRACT FROM PUBLISHER]

Power line communication (PLC) is the use of power lines for the purpose of electronic data transmission. The presence of additive noise, namely, background noise and impulsive noise, significantly affects the performance of a PLC system. While the background noise is modeled by Nakagami- $m$ distribution, the impulsive noise is modeled using Middleton class A distribution. In this letter, we study the performance of a PLC system under the combined effect of Nakagami- $m$ background noise and Middleton class A impulsive noise assuming binary phase shift keying signaling. The probability density function of decision variable under the influence of additive noise (sum of background noise and impulsive noise) is derived. We also derive an analytical expression for the average bit error rate of the considered PLC system. The analytical expressions are validated by close matching to the simulation results. The analysis presented in this letter closely predicts the behavior of the PLC system under the combined effect of background and impulsive noises. [ABSTRACT FROM PUBLISHER]

Power line communication (PLC) utilizes power lines for transmission of power as well as data transmission. It is an emerging field of communication for the home area network of smart grid. The performance of a PLC system is significantly affected by the additive and multiplicative power line noises; the additive noises are of two types, namely background noise and impulsive noise. Whereas, the multiplicative PLC noise leads to fading in the received signal strength. This paper provides the performance analysis of a PLC system over Rayleigh fading channel under Nakagami- $m$ distributed additive background noise assuming binary phase shift keying modulation scheme. The probability density function of the decision variable is derived. We obtain a numerically computable expression of the analytical average bit error rate of the considered system. The closed-form expression of the outage probability of the PLC system is also computed. Simulation results closely verify the validity of the derived analytical expressions. [ABSTRACT FROM PUBLISHER]

Power line communication (PLC) technology is used in various areas of a smart grid. The extensive use of PLC technology has proved its key role in smart grids throughout the world. Despite PLC's advantages, it suffers from a difficulty in modeling and analysis of its power line channel. Many researchers have experimented and proposed channel models for their own defined environments; as a result, a unified model for the power line has not been presented. To overcome this problem partially, we used a Nakagami-m distribution like background noise and analyzed the performance of the binary transmission system in our previous work. In this paper, we compare the analytical and simulated BER (bit error rate) performances of QPSK (quadrature phase shift keying) transmission system with Gray encoding. We verify that the analyzed and simulated performances are well matched for different values of m. [ABSTRACT FROM AUTHOR]

Abstract: This paper carries out the integration of a space–time block code (STBC) technique into a chaos shift keying (CSK) system. To that end, an Alamouti space–time code scheme is combined with the CSK system for two transmit and two receiver antennas. Our proposed scheme is a simple configuration that combines the advantages of STBC and chaotic modulation. Because the chaotic signals have a low cross-correlation, the Alamouti-CSK scheme can suppress the inter-transmit–antenna interference, recover the transmitted symbols and achieve the full diversity gain, all in outstanding fashion. Once the design of Alamouti-CSK system is presented, the performance of the proposed system is analyzed under a slow fading channel. A computation approach of the bit error rate (BER) expression based on the probability density function of the bit energy of the chaotic sequence is presented. Simulation results prove the accuracy of our BER computation methodology. [Copyright &y& Elsevier]

The distributions of random variables are of interest in many areas of science. In this paper, ascertaining on the importance of multi-hop transmission in contemporary wireless communications systems operating over fading channels in the presence of cochannel interference, the probability density functions (PDFs) of minimum of arbitrary number of ratios of Rayleigh, Rician, Nakagami-m, Weibull and α-μ random variables are derived. These expressions can be used to study the outage probability as an important multi-hop system performance measure. Various numerical results complement the proposed mathematical analysis. [ABSTRACT FROM AUTHOR]

In this paper, a general small-scale fading model for wireless communications, that explores the nonlinearity and at the same time the inhomogeneous nature of the propagation medium, is presented, studied in terms of its first-order statistics of the envelope, and validated by means of field measurements and the Monte Carlo simulation. It is indeed a novel distribution with many advantages such as its generality, its physical interpretation that is directly associated with the propagation channel, and its mathematical tractability due to its simple and closed-form expression. By fitting to measurement data, it has been shown that the proposed distribution outperforms the widely known fading distributions. Namely, the α − λ − μ model, which can be in fact called α − η − μ format 2 model, can also be obtained from the α − η − μ format 1 model by a rotation of the axes. Both formats are combined, in order to result to a unified model in a closed form that may describe the propagation environment in a variety of different fading conditions. Its physical background is hidden behind the names of its parameters. The unified model includes the already known general distributions α − μ′, η − μ, λ − μ ( η − μ format 2), and their inclusive ones as special cases. [ABSTRACT FROM AUTHOR]

In this study, two-parameter Nakagami-m distribution has been introduced along with two-parameter gamma (GM), three-parameter generalized logistic (GLG), three-parameter Pearson type 3 (PT3), and three-parameter generalized extreme value distributions for the derivation of flood hydrographs for gauged catchments. Parameters of these distributions have been optimized using genetic algorithm (GA) in MATLAB v. 7.1 GA toolbox. Observed storm events of three catchments have been used to evaluate the efficiency of the hydrographs generated by these distributions. A validation test has been performed on the different storm event data set of one of the catchments and results were found satisfactory. Statistical estimators (viz., coefficient of efficiency, root-mean squared error, and mean absolute percent error), which indicate the efficiency of the optimization technique in deriving flood hydrographs have been used to find out the rank of these distributions for deriving the hydrographs for the particular catchments. [ABSTRACT FROM AUTHOR]

The optimality of nondynamic DF relaying over a general three-node Nakagami fading channel in terms of the diversity-multiplexing tradeoff (DMT) is established. In particular, when the fading of the relay-source link is less severe than that of the relay-destination link, both orthogonal and nonorthogonal DF protocols are shown to be DMT-optimal over certain ranges of the multiplexing gains. It is also shown that when the multiplexing gains are sufficiently high, the DMT of the DF protocols is completely independent of the statistical properties of the relay-destination link. [ABSTRACT FROM AUTHOR]

The performance of switch-and-examine diversity (SED) over L arbitrarily correlated and not necessarily identically distributed Nakagami-m fading channels is studied. Analytical expressions for the distribution of the SED output signal-to-noise ratio (SNR) are obtained for the constant correlation model. For the most general case of arbitrary correlation, by assuming half-integer or integer values for the fading parameterm, analytical expressions for the distribution of the output SNR with L ≤ 3 are derived. Moreover, for L>3, analytical approximations for the output SNR are presented. The derived expressions are used to study the outage and average symbol error probability of SED receivers. Performance results obtained by numerical evaluation and verified by means of computer simulations show that the performance of the receivers under consideration is degraded with increasing branch correlation. Nevertheless, SED receivers outperform uncorrelated switch-and-stay diversity receivers, even when they operate under high branch correlation. [ABSTRACT FROM AUTHOR]

This paper studies the ergodic capacity limits of multiple-input multiple-output (MIMO) antenna systems with arbitrary finite number of antennas operating on general fading environments. Through the use of majorization theory, we first investigate in detail the ergodic capacity of Nakagami-m fading channels, for which we derive several ergodic capacity upper and lower bounds. We then show that a simple expression for the capacity upper bound is possible for high signal-to-noise ratio (SNR), which permits to analyze the impact of the channel fading parameter in on the ergodic capacity. The asymptotic behavior of the capacity in the large-system limit in which the number of antennas at one or both side(s) goes to infinity, is also addressed. Results demonstrate that the capacity scaling laws for Nakagami-m and Rayleigh-fading MIMO channels are identical. Finally, we employ the same technique to distributed MIMO (D-MLMO) systems undergoing composite log-normal and Nakagami fading, where we derive similar ergodic capacity upper and lower bounds. Monte Carlo simulation results are provided to verify the tightness of the proposed bounds. [ABSTRACT FROM AUTHOR]

This paper presents the multiple-input multiple-output (MIMO) channel capacity over the Nakagami-m fading channel. The joint eigenvalue density function of W = HH†, where H is the channel matrix, is derived in closed form for H (2 x 2) and any integer values of m, as well as for H (2 x 3) with m = 2 and m = 3. The marginal eigenvalue distribution of W is also derived in a closed-form expression. All the results are validated by numerical Monte Carlo simulations and are in excellent agreement. [ABSTRACT FROM AUTHOR]

This paper presents two general fading distributions, the κ-μ distribution and the η-μ distribution, for which fading models are proposed. These distributions are fully characterized in terms of measurable physical parameters. The κ-μ distribution includes the Rice (Nakagami-n), the Nakagami-m, the Rayleigh, and the One-Sided Gaussian distributions as special cases. The η-μ distribution includes the Hoyt (Nakagami-q), the Nakagami-m, the Rayleigh, and the One-Sided Gaussian distributions as special cases. Field measurement campaigns were used to validate these distributions. It was observed that their fit to experimental data outperformed that provided by the widely known fading distributions, such as the Rayleigh, Rice, and Nakagami-m. In particular, the κ-μ distribution is better suited for line-of-sight applications, whereas the η-μ distribution gives better results for non-line-of-sight applications. [ABSTRACT FROM AUTHOR]

This paper introduces a fading model, which explores the nonlinearity of the propagation medium. It derives the corresponding fading distribution—the α-μ distribution-which is in fact a rewritten form of the Stacy (generalized Gamma) distribution. This distribution includes several others such as Gamma (and its discrete versions Erlang and central Chi-squared), Nakagami-m (and its discrete version Chi), exponential, Weibull, one-sided Gaussian, and Rayleigh. Based on the fading model proposed here, higher order statistics are obtained in closed-form formulas. More specifically, level-crossing rate, average fade duration, and joint statistics (joint probability density function, general joint moments, and general correlation coefficient) of correlated α-μ variates are obtained, and they are directly related to the physical fading parameters. [ABSTRACT FROM AUTHOR]

Body worn wireless sensors for monitoring health information is a promising new application. In developing these sensors, a communication channel model is essential. However, there are currently few measurements or models describing propagation around the body. To address this problem, we have measured electromagnetic waves near the torso and derived relevant statistics. We find that components diffracting around the body are well modeled using correlated log normal variables, and a Nakagami-m distribution can be used to incorporate the influence of arm motions. We have implement this model and evaluated it in terms of important communication metrics. This paper describes body area propagation statistics and proposes a suitable computer model implementation. [ABSTRACT FROM PUBLISHER]

This letter studies the diversity advantage of single and multiuser systems utilizing multiple-input multiple-output (MIMO) antennas for known channels at the transmitter and receiver(s) by investigating the overall distribution of the resulting channel. For the single-user case, the resultant channel is taken as the largest singular value of the MIMO channel whereas for the multiuser scenario, the resultant channel is obtained by a recently proposed joint-channel diagonalization. The channel distribution is studied using hypothesis testing with the hypothesis that the distribution follows a Nakagami-m distribution with given parameters. It is concluded from the chi-square goodness-of-fit test that the distribution of the resultant channel for single or multiuser MIMO channel is well matched with a Nakagami-m distribution. [ABSTRACT FROM PUBLISHER]

In this paper, we analyze the performance of a full duplex (FD) relay assisted mixed radio frequency (RF)/free space optical (FSO) system with self-interference. The RF links follow Nakagami-m distribution, and FSO links adopt Gamma–Gamma atmospheric turbulence model. We derive the exact and asymptotic outage probability (OP) expressions of the system. Based on the cumulative distribution function (CDF), the bit error rate (BER) and average capacity expressions are further presented. To verify the superiority of FD relay system, we deduce the average capacity of half duplex (HD) relay system and investigate the performance differences between FD relay system and HD relay system. Furthermore, the residual self-interference condition is discussed in this paper. Simulation results show that, when the self-interference coefficient (SIC) is large, the capacity of FD relay system declines severely and behaves even worse than HD relay system. Moreover, there is a tradeoff between SIC and system performance, because the transmission power of the second hop RF link is also the self-interference of the first hop. • A full duplex relay assisted mixed RF/FSO system with self-interference is proposed and analyzed. • Expressions for OP, BER, and average capacity are derived and simulated. • The effects of self-interference and residual self-interference on system performance are discussed. [ABSTRACT FROM AUTHOR]