Correlated Weibull Fading Channels Research Articles

Performance Analysis of a Selection Combining System That Uses the Minimal Interference Algorithm

In this paper, a new combining algorithm for selection combining (SC) receiver based on selection of diversity branch with the lowest interference is proposed. The system used for analysis consists of dual-branch SC diversity that operates over correlated Weibull fading channels. Closed-form expressions for joint probability density function (PDF) of desired signal and interference at the output and PDF of instantaneous signal-to-interference ratio (SIR) at the output are obtained and used to investigate important system performance indicators. System performance is analyzed using outage probability, average bit error probability (ABEP) and average output SIR. The obtained results are compared with the previously published for the SIR algorithm employed by the same system.

PERFORMANCE COMPARISON OF DUAL-BRANCH AND TRIPLE-BRANCH SELECTION DIVERSITY RECEIVER BASED ON DESIRED SIGNAL ALGORITHM OVER CORRELATED WEIBULL FADING CHANNELS

As an important performance measure, in this paper the outage probability of dual- and triple-branch selection combining (SC) diversity system is compared. The analyzed system works over correlated Weibull fading channels in the presence of cochannel interference (CCI) where the output signal choice is done using desired signal algorithm. Results are graphically presented showing the influence of number of diversity branches, correlation coefficient and ratio of average powers of desired and interference signal.

Multiple Co-Channel Interferers Influence on Selection Combining over Correlated Weibull Fading Channels

In this paper, we provide performance analysis of signal-to-interference ratio (SIR) based selection combining (SC) receiver, operating over correlated Weibull fading channels, with an arbitrary number of correlated co-channel interferers, over each branch. Assuming this multibranch diversity technique, infinite series expressions were derived for PDF (probability density function) and CDF (cumulative distribution function) of the output SIR. The proposed analysis was used for evaluating outage probability (OP). The effects of various system parameters, such as number of multiple interferers, correlation level and fading severity on the OP, are graphically presented. Another important system performance measure, average bit error probability (ABER) is efficiently evaluated for modulation schemes such as binary frequency-shift keying (BFSK) and binary differentially phase-shift keying (BDPSK).

New Representations for the Gaussian Class Multivariate Weibull Distribution with Constant Correlation and Applications

Novel single-integral representations for the multivariate probability density functions (PDFs) and cumulative distribution functions (CDFs) of the Gaussian class Weibull distribution are derived. The solutions are expressed in terms of familiar mathematical functions which are available in common mathematical software. The well known equal (constant) correlation model is considered. A special linear transformation of independent Gaussian random variables is used to generate correlated Weibull random variables. The advantage of the new representation is that only a single integral computation is needed to compute a N-dimensional distribution. The new representation of the CDF is used for the performance evaluation of a selection diversity combiner operating in equally correlated Weibull fading channels. The new PDF representation is also used for an analysis of the moments of the output signal-to-noise ratio of an equal-gain diversity combiner operating in equally correlated Weibull fading channels.

Performance analysis of dual switched diversity over correlated Weibull fading channels with co‐channel interference

AbstractThis paper studies the performance of switch and stay combining (SSC) diversity in the presence of co‐channel interference over correlated Weibull fading channels. SSC diversity based on signal‐to‐interference ratio (SIR) is a low‐complexity and a very efficient technique that reduces fading and co‐channel interference influence. New closed‐form expressions for the probability density function and cumulative distribution function of the output SIR's are derived. These formulas are used in a detailed analysis of the average output SIR and outage probability. The influence of fading severity and correlation coefficient on the optimum switching threshold and system performance is investigated. Monte Carlo simulations are performed to verify obtained theoretical results and determine average bit error rate in detecting binary phase‐shift keying (BPSK), differential BPSK and quadrature amplitude modulation signals. Copyright © 2011 John Wiley & Sons, Ltd.

On the Effect of Imperfect Cophasing in MRC and EGC Receivers Over Correlated Weibull Fading

This paper presents a comparative analysis of dual-branch maximal-ratio combining (MRC) and equal-gain combining (EGC) receivers with coherent modulations over correlated Weibull fading channels. The numerical and simulations results show the influence of imperfect cophasing, branch unbalancing and correlation on the error performance. It is interestingly shown that EGC has lower irreducible error floor than MRC in the presence of incoherent combining, while the higher value of the correlation coefficient results to lower irreducible error floor. Furthermore, the unbalance parameter has practically no influence on the irreducible error floor.

Performance analysis of system with triple selection combining over correlated Weibull fading channel in the presence of cochannel interference

In this paper, closed-form expressions for probability density function (PDF) and cumulative distribution function (CDF) of the signal-to-interference ratio (SIR) at the output of the triple selection combining (SC) receiver over correlated Weibull fading channels in the presence of correlated cochannel interference (CCI) are derived. These expressions are used to study wireless system performance criteria, such as outage probability, average bit error probability and average output SIR. .

Performance analysis of system with L‐branch selection combining over correlated Weibull fading channels in the presence of cochannel interference

AbstractIn this paper, the performance of L‐branch selection combining receiver over correlated Weibull fading channels in the presence of correlated Weibull‐distributed cochannel interference is analyzed. Closed‐form expressions for probability density function and cumulative distribution function of the signal‐to‐interference ratio at the output of the selection combining receiver present main contribution of this paper. Numerical results are also presented to show the effects of various parameters as the fading severity, correlation and number of branches on outage probability. Copyright © 2009 John Wiley & Sons, Ltd.

General exact and accurate approximate formulations for the crossing rates of multibranch diversity receivers over non-identical correlated Weibull channels

General exact expressions for the average level crossing rate (LCR) of multibranch selection (SC), equal-gain (EGC), and maximal-ratio (MRC) combiners operating over non-identical correlated Weibull fading channels are provided. They are given in terms of finite-range multifold integrals. Our exact formulations generalize those obtained recently in the literature for the dual-branch case. The exact solution requirements are then loosened to allow for simpler accurate approximate expressions. They appear in a fairly simple closed-form fashion, for the SC, and still as multiple integrals, for the EGC and MRC, but with much simpler integrands, which drastically reduces the calculation time. Sample numerical results are discussed by specializing the general expressions to a space-diversity system using three collinear horizontally spaced omnidirectional antennas at the mobile station.

General Exact Level Crossing Rate and Average Fade Duration for Dual-Diversity Combining of Nonidentical Correlated Weibull Signals

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper derives general <emphasis emphasistype="boldital">exact</emphasis> expressions for the level crossing rate (LCR) and the average fade duration (AFD) of dual-branch selection, equal-gain, and maximal-ratio combiners operating over nonidentical correlated Weibull fading channels. Sample numerical results are discussed by specializing the general expressions to a space-diversity system using horizontally spaced antennas at a mobile station. It is verified that as the antenna spacing becomes larger, the LCR decreases, becoming oscillatory and convergent. In addition, when the direction of the mobile is perpendicular to the axis of the antenna, the AFD is loosely dependent on the antenna spacing. Some simulation results are presented to verify the correctness of the analytical formulation. </para>

Performance analysis of system with selection combining over correlated Weibull fading channels in the presence of cochannel interference

Selection diversity based on the signal to interference ratio (SIR) is a very efficient technique that reduces fading and channel interference influence. In this paper, system performances of selection combining and correlated Weibull channels are analyzed. Fading between the diversity branches and between interferers is correlated and Weibull distributed. Very useful closed-form expressions are obtained for the output SIR's probability density function (PDF) and cumulative distribution function which is main contribution of this paper. Outage probability, the average output SIR, and the average error probability for coherent, noncoherent modulation are derived. Numerical results presented in this paper point out the effects of fading severity and correlation on the system performances.

Channel capacity and digital modulation schemes in correlated Weibull fading channels with nonidentical statistics

The novel closed –form expressions for the average channel capacity of dual selection diversity is presented, as well as, the bit-error rate (BER) of several coherent and noncoherent digital modulation schemes in the correlated Weibull fading channels with nonidentical statistics. The results are expressed in terms of Meijer's Gfunction, which can be easily evaluated numerically. The simulation results are presented to validate the proposed theoretical analysis and to examine the effects of the fading severity on the concerned quantities.

Comments on “Average LCR and AFD for SC diversity over correlated Weibull fading channels”

In a recent paper, two formulae for the average level crossing rate and fade duration at the output of dual-branch selection diversity receivers have been derived. In this short communication, some previously published works including results being in a more general setting are reviewed and compared.

On the Multivariate Weibull Fading Model With Arbitrary Correlation Matrix

An efficient approximation for the multivariate Weibull distribution with arbitrary correlations is presented. By approximating the Gaussian correlation matrix with a Green's matrix, a useful analytical expression for the joint distribution of the fading envelopes is derived. As an application, the outage performance of multibranch receivers operating over arbitrarily correlated Weibull fading channels is studied. Numerical and computer simulation results are presented and compared to illustrate the accuracy of the proposed approximation

Average LCR and AFD for SC Diversity Over Correlated Weibull Fading Channels

The analytic methods of average LCR (Level Crossing Rate) and AFD (Average Fading Duration) are applied in the analysis for the SC (Selection Combining) diversity, which works over the correlated Weibull statistics channel. The dual branch SC diversity was used to prove the accuracy of the derived theoretical formula in this paper. We adopt different probability density functions (pdf) and cumulate distribution functions (CDF) to show the Moreover, the numerical results obtained from computer are verified to the published researches.

Performance of dual maximal ratio combining diversity in nonidentical correlated Weibull fading channels using Pade/spl acute/ approximation

In this letter, we evaluate the performance of the dual-branch maximal ratio combining (MRC) diversity scheme in nonidentical correlated Weibull fading channels with arbitrary parameters. We first use the Pade/spl acute/ approximation (PA) to find closed-form rational expressions for the moment generating function (MGF) of the output signal-to-noise ratio (SNR) of the MRC receiver. Different performance measures, such as the outage probability and the average symbol-error rate for different linear modulations, are then presented using the well-known MGF approach. Furthermore, the effect of the input SNRs unbalancing, the severity of fading, and the degree of correlation on the system performance are also studied. Our results are validated by comparing them with computer simulations, and we show that the PA technique is indeed a convenient tool for such performance evaluation studies.

Gaussian Class Multivariate Weibull Distributions: Theory and Applications in Fading Channels

Ascertaining on the suitability of the Weibull distribution to model fading channels, a theoretical framework for a class of multivariate Weibull distributions, originated from Gaussian random processes, is introduced and analyzed. Novel analytical expressions for the joint probability density function (pdf), moment-generating function (mgf), and cumulative distribution function (cdf) are derived for the bivariate distribution of this class with not necessarily identical fading parameters and average powers. Two specific distributions with arbitrary number of correlated variates are considered and studied: with exponential and with constant correlation where their pdfs are introduced. Both cases assume equal average fading powers, but not necessarily identical fading parameters. For the multivariate Weibull distribution with exponential correlation, useful corresponding formulas, as for the bivariate case, are derived. The presented theoretical results are applied to analyze the performance of several diversity receivers employed with selection, equal-gain, and maximal-ratio combining (MRC) techniques operating over correlated Weibull fading channels. For these diversity receivers, several useful performance criteria such as the moments of the output signal-to-noise ratio (SNR) (including average output SNR and amount of fading) and outage probability are analytically derived. Moreover, the average symbol error probability for several coherent and noncoherent modulation schemes is studied using the mgf approach. The proposed mathematical analysis is complemented by various evaluation results, showing the effects of the fading severity as well as the fading correlation on the diversity receivers performance.

Performance Analysis of Dual Selection Diversity in Correlated Weibull Fading Channels

Ascertaining the importance of the dual selection combining (SC) receivers and the suitability of the Weibull model to describe mobile fading channels, we study the performance of a dual SC receiver over correlated Weibull fading channels with arbitrary parameters. Exact closed-form expressions are derived for the probability density function, the cumulative distribution function, and the moments of the output signal-to-noise ratio (SNR). Important performance criteria, such as average output SNR, amount of fading, outage probability, and average bit-error probability for several modulation schemes are studied. Furthermore, for these performance criteria, novel closed-form analytical expressions are derived. The proposed analysis is complemented by various performance evaluation results, including the effects of the input SNR's unbalancing, fading severity, and fading correlation on the overall system's performance. Computer simulation results have verified the validity and accuracy of the proposed analysis.