Sadra Kashef - Academia.edu (original) (raw)

Papers by Sadra Kashef

Optics Express, 2010

There has been a trend of migration to high spectral efficiency transmission in optical fiber com... more There has been a trend of migration to high spectral efficiency transmission in optical fiber communications for which the frequency guard band between neighboring wavelength channels continues to shrink. In this paper, we derive closed-form analytical expressions for nonlinear system performance of densely spaced coherent optical OFDM (CO-OFDM) systems. The closed-form solutions include the results for the achievable Q factor, optimum launch power density, nonlinear threshold of launch power density, and information spectral efficiency limit. These analytical results clearly identify their dependence on system parameters including fiber dispersion, number of spans, dispersion compensation ratio, and overall bandwidth. The closed-form solution is further substantiated by numerical simulations using distributed nonlinear Schrödinger equation.

2013 IEEE 11th Malaysia International Conference on Communications (MICC), 2013

ABSTRACT In this paper, we propose a Cumulant Kolmogorov-Smirnov (KS) test for spectrum sensing i... more ABSTRACT In this paper, we propose a Cumulant Kolmogorov-Smirnov (KS) test for spectrum sensing in Cognitive Radio networks. The KS test is a kind of goodness of fit test that quantifies a distance between the empirical distribution functions of the received signals and the channel noise samples. Due to using 4th order Cumulant statistics, the proposed KS detector has some advantages over previous detectors. We exert KS test to the estimated Cumulant vector and perform detection problem. The proposed method is nonparametric and needs only a short sequence of noise samples. In addition, it is not sensitive to noise uncertainty. Superiority of the proposed KS-based method is shown by comparing it with a popular KS method and the classical Energy Detector.

2013 Ieee 11th Malaysia International Conference on Communications, Nov 1, 2013

ABSTRACT In this paper, goodness-of-fit (GoF)-based spectrum sensing problem is investigated for ... more ABSTRACT In this paper, goodness-of-fit (GoF)-based spectrum sensing problem is investigated for detection of orthogonal frequency-division multiplexing (OFDM) signals. In essence, some novel local sensing approaches based on Shapiro-Wilk (SW), Shapiro-Francia (SF), lilliefors (LI), and Jarque-Bera (JB) tests are offered. Then, we propose a mixed approach based on SW and SF tests. These methods do not require any prior information about the primary signals. In addition, the order of computational complexity of the offered methods is computed and demonstrated that proposed methods have less complexity order and fast performance in comparison with the AndersonDarling method. Finally, the detection performance of the proposed methods is evaluated through simulations. The results demonstrate the superiority of the mixed method.

2014 22nd Iranian Conference on Electrical Engineering (ICEE), 2014

There has been a trend of migration to high spectral efficiency transmission in optical fiber com... more There has been a trend of migration to high spectral efficiency transmission in optical fiber communications for which the frequency guard band between neighboring wavelength channels continues to shrink. In this paper, we derive closed-form analytical expressions for nonlinear system performance of densely spaced coherent optical OFDM (CO-OFDM) systems. The closed-form solutions include the results for the achievable Q factor, optimum launch power density, nonlinear threshold of launch power density, and information spectral efficiency limit. These analytical results clearly identify their dependence on system parameters including fiber dispersion, number of spans, dispersion compensation ratio, and overall bandwidth. The closed-form solution is further substantiated by numerical simulations using distributed nonlinear Schrödinger equation.

Optics Express, 2010

There has been a trend of migration to high spectral efficiency transmission in optical fiber com... more There has been a trend of migration to high spectral efficiency transmission in optical fiber communications for which the frequency guard band between neighboring wavelength channels continues to shrink. In this paper, we derive closed-form analytical expressions for nonlinear system performance of densely spaced coherent optical OFDM (CO-OFDM) systems. The closed-form solutions include the results for the achievable Q factor, optimum launch power density, nonlinear threshold of launch power density, and information spectral efficiency limit. These analytical results clearly identify their dependence on system parameters including fiber dispersion, number of spans, dispersion compensation ratio, and overall bandwidth. The closed-form solution is further substantiated by numerical simulations using distributed nonlinear Schrödinger equation.

2013 IEEE 11th Malaysia International Conference on Communications (MICC), 2013

ABSTRACT In this paper, we propose a Cumulant Kolmogorov-Smirnov (KS) test for spectrum sensing i... more ABSTRACT In this paper, we propose a Cumulant Kolmogorov-Smirnov (KS) test for spectrum sensing in Cognitive Radio networks. The KS test is a kind of goodness of fit test that quantifies a distance between the empirical distribution functions of the received signals and the channel noise samples. Due to using 4th order Cumulant statistics, the proposed KS detector has some advantages over previous detectors. We exert KS test to the estimated Cumulant vector and perform detection problem. The proposed method is nonparametric and needs only a short sequence of noise samples. In addition, it is not sensitive to noise uncertainty. Superiority of the proposed KS-based method is shown by comparing it with a popular KS method and the classical Energy Detector.

2013 Ieee 11th Malaysia International Conference on Communications, Nov 1, 2013

ABSTRACT In this paper, goodness-of-fit (GoF)-based spectrum sensing problem is investigated for ... more ABSTRACT In this paper, goodness-of-fit (GoF)-based spectrum sensing problem is investigated for detection of orthogonal frequency-division multiplexing (OFDM) signals. In essence, some novel local sensing approaches based on Shapiro-Wilk (SW), Shapiro-Francia (SF), lilliefors (LI), and Jarque-Bera (JB) tests are offered. Then, we propose a mixed approach based on SW and SF tests. These methods do not require any prior information about the primary signals. In addition, the order of computational complexity of the offered methods is computed and demonstrated that proposed methods have less complexity order and fast performance in comparison with the AndersonDarling method. Finally, the detection performance of the proposed methods is evaluated through simulations. The results demonstrate the superiority of the mixed method.

2014 22nd Iranian Conference on Electrical Engineering (ICEE), 2014

There has been a trend of migration to high spectral efficiency transmission in optical fiber com... more There has been a trend of migration to high spectral efficiency transmission in optical fiber communications for which the frequency guard band between neighboring wavelength channels continues to shrink. In this paper, we derive closed-form analytical expressions for nonlinear system performance of densely spaced coherent optical OFDM (CO-OFDM) systems. The closed-form solutions include the results for the achievable Q factor, optimum launch power density, nonlinear threshold of launch power density, and information spectral efficiency limit. These analytical results clearly identify their dependence on system parameters including fiber dispersion, number of spans, dispersion compensation ratio, and overall bandwidth. The closed-form solution is further substantiated by numerical simulations using distributed nonlinear Schrödinger equation.