Haleh Karkhaneh

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In this paper an injection-locked optical orthogonal frequency-division multiplexing (ILO-OFDM) method is presented using an optically injection-locked laser. In an ILO-OFDM system, an optically injected semiconductor laser operating in stable locking is utilized to directly modulate the OFDM signal on the optical carrier intensity. To design this system,(More)
In this paper we present a modified model of solid state power amplifiers. Also using the mathematical concept of best approximation in Hilbert spaces, a predistorter structure is suggested to compensate both AM/AM and AM/PM conversion characteristics of a solid state power amplifier. To verify the effects of this linearization we generally consider it in a(More)
This paper represents a new adaptive method to model the nonlinearity of power amplifiers(PAs) with memory effects based on Wiener approach and also adaptive predistorter to counterbalance the AM/AM and AM/PM nonlinear effects of the transmitter power amplifier is proposed by Hammerstein approach. Finally we consider the effectiveness of proposed method on(More)
This paper is concerned with a new time-domain modeling topology for signals which is applied to wideband power amplifiers. The memory effect will be shown using two-tone intermodulation distortion (IMD) measurement with different tone frequency spacing and power levels. The model is developed by using a memoryless nonlinearity followed by a dynamic LTI(More)
OFDM (Orthogonal Frequency-Division Multiplexing) is a wideband digital modulation scheme which is critically dependent on linearity in the hardware system, due to its reliance on Fourier Transformation and its inherently high peak-to-average power ratio (PAPR), and minimization of nonlinearity is thus a priority. In this paper the effectiveness of a(More)
Using the mathematical concept of best approximation in Hilbert spaces a predistorter structure is suggested to compensate both AM/AM and AM/PM conversion characteristics of a solid state power amplifier. To verify the effects of this linearization we generally consider it in a QAM signal transmission in an additive white Gaussian noise channel. The results(More)
OFDM (Orthogonal Frequency-Division Multiplexing) is a wideband digital modulation scheme that has resilience to multipath effects and is one of the most influential such schemes for modern wireless network systems. The scheme is critically dependent on linearity in the hardware system, due to its reliance on Fourier Transformation and its inherently high(More)
The nonlinear characteristic of an laser diode, LD, impacts on the performance of optical wireless systems using OFDM (orthogonal frequency division multiplexing). First, the influence of the nonlinear characteristic on bit-error performance is analyzed using a high power LD (LML-808.7B-XX). Next, the paper proposes a predistorter to compensate the(More)
A novel injection-locked optical orthogonal frequencydivision multiplexing (ILO-OFDM) method using an optically injection-locked semiconductor laser is presented in this paper. In this system, an optically injected semiconductor laser under stable locking takes the role of an optical modulator to directly impose the OFDM signal on the optical carrier(More)
This paper investigates the performance of wavelet OFDM signals over a wireless communications link. The scheme is shown to be generally similar to Fourier based OFDM, but with some additional features, and improved characteristics. The sensitivity of both schemes to the nonlinear amplification in the transmitter is compared by monitoring the time domain(More)
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