Performance of Two-Hop DS-CDMA Systems Using Amplify-and-Forward Protocol over Different Fading Channels

This study analyses the performance of directsequence code division multiple access (DS-CDMA) based on two-hop amplify-and-forward protocol over Weibull symmetric fading channels as well as Rayleigh/Rician, Rician/Rayleigh asymmetric fading phenomenas. We investigate the bit-error rate (BER) of the considered system using multiple relays by considering the effect of Weibull fading parameter and Rician K factor on the system performance. Our simulation results demonstrate the positive impacts of the value of fading parameter, Rician K factor and increasing number of relay nodes on BER performance. It is also confirmed that the Rician K factor is more effective on the system performance over Rician/Rayleigh fading channels in comparison with Rayleigh/Rician fading environment

Error Probability Analysis of a Composite Weibull/Log-Normal Fading Channel

In this study, error probability of a single-input single-output (SISO) system is investigated over a composite Weibull/log-normal fading channel. We aim to study a SISO system in the composite Weibull/log-normal composite fading model which is useful in characterizing fading effects in numerous realistic communication scenarios. Therefore, a closed-form error probability expression was derived by using cumulative distribution function (CDF) of a Weibull/log-normal fading channel. The proposed error probability expression is based on CDF and is valid for different binary digital modulation types. Results that are given in this study were confirmed by computer simulations

A New Nakagami-m Inverse CDF Approximation Based on the Use of Genetic Algorithm

The inverse cumulative distribution function (CDF) appears in many important problems such as outage probability calculations in wireless communications. The Nakagami-m inverse CDF is difficult to compute numerically and is known to have no closed form. In this paper, we present a new and useful approximation to the Nakagami-m inverse CDF. The genetic algorithm is applied to optimize the coefficients of the proposed approximation. For typical cases in Nakagami-m wireless communication channels, it is shown through comprehensive computer simulations that the proposed method has high accuracy in most of the region of the exact CDF values

Beaulieu-Xie Gölgelemeli Sönümlü Kanallar İçin Efektif Kanal Kapasite İfadesinin Kuramsal Türetimi

Bu çalışma, alıcı-verici arasındaki hattın tek ve Beaulieu-Xie gölgelemeli (BX-shadowed, BX-S) sönümlenmeye sahip olduğu bir sistem için efektif kanal kapasitesi (effective channel capacity, Ceff) analizini sunmaktadır. Çalışmada Ceff ifadesi kuramsal olarak türetilmekte, türetimler için BX-S sönümlenmesine ait olasılık yoğunluk fonksiyonundan (probability density function, PDF) yararlanılmaktadır. Ceff ifadesinin doğruluğu bilgisayar benzetimleri ile gösterilmeye çalışılmakta, farklı parametre değişimleri ile çeşitli senaryolar incelenmektedir

Improved Chernoff Bound of Gaussian Q-function with ABC algorithm and its QAM applications to DB SC and MRC systems over Beaulieu–Xie channels

In this study, we propose an improved upper bound for the Gaussian Q function by using artificial bee colony algorithm. Then, we investigate the performance of the dual-branch (DB) selection combining (SC) and maximal ratio combining (MRC) systems over the Beaulieu–Xie fading channels. The probability density functions of the instantaneous signal to noise ratio for the considered systems are obtained. Employing the proposed upper bound, we derive closed-form expressions of the error probability for the quadrature amplitude modulation (QAM) techniques such as rectangular QAM (RQAM), cross QAM (XQAM), and hexagonal QAM (HQAM). Furthermore, the asymptotic error probability expressions for the DB SC system are also obtained to simplify the analyses. The effects of some key parameters in the systems are shown in the results. Comparisons of the different modulation types and the different upper bound approaches for the Gaussian Q function are presented. Finally, it has been shown that the upper bound approximation presented in this study can be widely used for many communication applications

1 Interactive Fuzzy Goal Programming Based on Jacobian Matrix to Solve Decentralized Bi-level Multi-objective Fractional Programming Problems

This paper attempts to shed light on solving decentralized bi-level multi-objective fractional programming problems (DBL-MOFPP) with single decision maker at the first level and multiple decision makers at the second level. In this paper, we proposed a fuzzy goal programming (FGP) based on Jacobian matrix for DBL-MOFPP. In the proposed approach, membership functions are associated for the fuzzy goals of all objectives at two levels and they are linearized using a Jacobian matrix. Then FGP approach is used to achieve highest degree of each of the membership goals by obtaining the most satisfactory solution for all decision makers. We used known numerical example and practical application in order to show the efficiency and superiority of the proposed approach. Sensitivity analysis with variation of tolerance values on decision functions is performed to present how the solution is sensitive to the change of tolerance values

Asimetrik Sönümlü Kanallarda İki Atlamalı Çöz-ve-Aktar Röleli İletimin Servis-dışı Kalma Olasılığının Analizi

Bu çalışma, iki atlamalı çöz-ve-aktar röleli iletim modelininasimetrik sönümlü kanallarda servis-dışı kalma olasılığınısunmaktadır. Ele alınan işbirlikli sistem, bir kaynak (S), birröle (R) ve bir hedeften (D) oluşmaktadır. İncelenen asimetriksenaryoya göre, kaynak-röle ve röle-hedef arasında bulunankanallar sırasıyla Rayleigh ve genelleştirilmiş Gammasönümlenmesine sahiptir. İşbirlikli sistemin servis-dışı kalmaolasılığı için analitik bir ifade türetilmiştir. Direk ve röleliiletimin servis-dışı kalma olasılığı için türetilen bu ifadekullanılarak nümerik sonuçlar verilmiştir.This work presents the outage probability of two-hop decodeand-forward (DF) relaying in asymmetric fading channels.Cooperation system considered in this work consists of asource (S), a relay (R) and a destination (D). According toasymmetric scenario assumed here, source-relay and relaydestinationlinks are subject to Rayleigh fading andgeneralized Gamma fading, respectively. An analyticalexpression is derived for the outage probability of consideredcooperation model and some numerical results of the outageprobability are presented for both direct transmission andDF relaying scheme by using the derived expression