Faramarz Asharif

Application of full-duplex wireless communication system on echo cancellation

In this paper, we intend to realize the data trading between the mobile station and the base station with only one frequency and in simultaneous process. Until now for transmitting and receiving the data, the mobile station and the base station have been used two different frequencies. This is obvious that by using two different frequencies in transceivers side there would be no interferences in transceiver itself. Therefore, utilization of different frequencies in transceiver was common. However, in these days due to the rapid increase of mobile station users, utilized frequencies between mobile and base stations should be allocated efficiently. Otherwise, it would reduce the speed of data sending in mobile stations. In order to get rid of this problem utilization of the same frequency in transmitter and receiver side is suggested. In this research utilization of the same frequency is considered for the mobile and the base station. However, there are near end echo occurs in system. Meanwhile, the echo canceller is implemented in the suggested system in order to cancel near end signal. In this paper, the considered algorithms of Echo canceller are Least Mean Square, Normalized Mean Square and Recursive Least Square. As a consequence, Normalized Least Mean Square Algorithm performed sufficiently to maintain an adequate low learning curve of normalized mean square error.

Design of Adaptive Friction Control of Small-Scaled Wind Turbine System Considering the Distant Observation

The aim of this research is to reduce down the angular velocity against strong wind during the storm considering the distant observation. Our expectation of this small-scaled wind turbine is to operate continuously even in storm days. However, since the small-scaled wind turbine consists of small blade, it may exceed the limitation of angular velocity in storm condition due to the low inertia moment and consequences of centrifugal force. So it would be broken down the system. Our target is to somehow reduce down the angular velocity using the stall factor control. Stall factor control mainly used in the junction of axis of blade of wind turbines gear wheel. Subsequently, the stall factor is operated when the angular velocity exceeds the limitation. Therefore, adaptive controller is designed and in order to evaluate the angular velocity’s behavior phase space method is introduced. As consequences, the stall factor preserves the stability and angular velocity performs under desired value constantly.

Analysis of Non-linear Adaptive Friction and Pitch Angle Control of Small-Scaled Wind Turbine System

The aim of this research is toanalyze the behavior of wind turbine system for passive and adaptive resistance non-linear control. In general, the wind turbine system is generating energy from the revolution of blades. The revolution of blades is depended on the velocity of wind. So, if we have strong wind then the revolution of blade is increased and in consequently more energy will generated. Therefore, usually the wind turbine systems are located in gale area in order to generate energy efficiency. However, there are limits of the revolution of blades or the angular velocity of blades. If the angular velocity exceeds the limit then wind turbine system may breakdown. Thus in this paper, in order to avoid the malfunction of wind turbine system, adaptive and passive non-linear control of resistance is considered. As consequences, the adaptive resistance has more stable and smooth angular velocity compare to passive resistance.

Stability and performacne analysis of passive and active stall control of small-scaled wind turbine system by phase plane method

The aim of this study is to reduce the angular velocity by controlling the stall factor even in storm condition. In this paper we intend to analyze the stability of angular velocity of small-scaled-wind turbine by phase plane method. Moreover, performance of angular velocity is evaluated by phase plane method. So far in the previous researches in order to determine the stability and evaluate the performance of nonlinear system time response of long term had been observed However, since pitch angle and angular velocity are significant factors of stability and performances, observation is an inadequate approach for certain analysis. Therefore, phase plane method is proposed to increase the analysis degrees of stability and performances simultaneously. The mathematical model of small scaled wind-turbine is considered to be a non-linear differential simultaneous equation. Stall Control is applied by implementing the shock absorber in the conjunction of blade and the turbine. Moreover, axis friction control is loaded to decrease the excessive revolution. The stability and performance of turbine is examined by several condition of stall factors. Eventually, we confirm the simplification of analysis for non-linear system.

Blind components processing a novel approach to array signal processing: A research orientation

Blind Components Processing (BCP), a novel approach in processing of data (signal, image, etc.) components, is introduced as well some applications to information communications technology (ICT) are proposed. The newly introduced BCP is with capability of deployment orientation in a wider range of applications. The fundamental of BCP is based on Blind Source Separation (BSS), a methodology which searches for unknown sources of mixtures without a prior knowledge of either the sources or the mixing process. Most of the natural, biomedical as well as industrial observed signals are mixtures of different components while the components and the way they mixed are unknown. If we decompose the signal into its components by BSS, then we can process the components separately without interfering the other components signal/data. Such internal access to signal components leads to extraction of plenty of information as well more efficient processing compared to normal signal processing wherein all the structure of the signal is gone under processing and modification. This manuscript besides the introducing BCP, proposes a practical applications of BCP with technical merit for harmonic noise cancellation as well stock pricing model.

Acoustic OFDM data embedding by reversible Walsh-Hadamard transform

The manuscripts presents a novel acoustic OFDM data embedding by deploying reversible Walsh-Hadamard transform. The classical acoustic OFDM embedding method was replacing the high band of the acoustic signal with power adjusted OFDM data which brings two shortcoming of degrading the spectral efficiency of the acoustic signal for the listener and dependency to the acoustic carrier signal for estimation of high band envelope. Despite the classical method, the proposed approach not only preserves the spectrum of the acoustic signal, but also it is independent from acoustic carrier signal. The proposed approach encodes the OFDM data signal by a weighted reversible Walsh-Hadamard transform via a linear combination of acoustic signal samples and OFDM signal samples. The efficiency of the approach in data transmission as well as listener subjective quality of acoustic carrier signal for different level of background noise has been clarified, and optimum values of the weighting matrix has been obtained by the evaluation of implementation of the system.

Improvement and comparison of Modulus Algorithm Blind Equalizer learning curve in time and frequency domain

In this paper, we intent to realize the unknown channel and equalize the distorted signal simultaneously. Therefore, channel estimation is required in order to equalize the signal in the receiver side. However, the problem is that there is no information about the reference signal. Therefore, Blind Equalizer is suggested. Blind equalizers do not require any known training sequence for the startup period, but can rather perform at any time the equalization directly on the data stream. Moreover, due to utilization of Blind Equalizer, the pilot signal can be cut off so that the amount of transmitted data is reduced. Thus faster computational process is expected compare to conventional equalizer. In this paper, conventional method of equalization, Constant Modulus Equalizer, Modified Constant Modulus Equalizer and frequency domain process of Constant Modulus Equalizer and Modified Constant Modulus Equalizer are introduced, respectively. In order to evaluate the each scheme, we have analyzed with a simple multipath channel and calculated the Normalized Mean Square Error (NMSE). Also the computational complexity is evaluated for suggested schemes. Consequently, the Modified Constant Modulus Equalizer in time domain performed the lowest NMSE among given method. However, computational complexity point view of this paper, Frequency Domain Modified Constant Modulus Equalizer has the lowest complexity.

Evaluation of Internal Model Controller in Time and Frequency Domain on Application to Wind Turbine

In this paper, we aim to stabilize and improve the performance of the system which includes time-delay elements in closed-loop system and uncertainty of the wind turbine system. Time-delay will happen during the long distance communication. By observing and controlling the attitude of wind turbine system from distance, the transmitted control input and output signal will be delayed certainly. For this reason it will be an unstable system by time-delay elements. So, here we consider Internal Model Controller (IMC) method which is one of the robust controllers. IMC method is composed of optimum controller and uncertainty model of plant and time-delay elements. The optimum controller is designed by minimizing the coefficients of external disturbance of output signal by H2 norm in order to stabilize the closed loop system considering the uncertainty of plant and predicted time-delay element and at the same time minimize the effects of time-delay element in sensitivity function. In this research controlling of the angular velocity and pitch angle of blade is considered. As consequences, angular velocity had better performance in nominal case compare to non-nominal case.

A fast and efficient adaptive channel equalizer for OFDM-based wireless relay system

Summary In this paper, we aim to eliminate the interference signals for a novel wireless communication repeater based on OFDM. The wireless repeater in communication system is important especially for mobile system. Now these days, in order to amplify the signal via repeater, receiver and transmitter of repeater using only one frequency without frequency shift. However, in this case repeater has problem that, amplified signal will feedback to receiver sides and this may cause the internal instability and distortion of repeater system. Therefore, by estimating the feedback signal by adaptive filter, we can eliminate the effects of feedback signal. In this paper we consider LMS, NLMS and RLS algorithms in order to estimate the feedback signal. Furthermore, by these adaptive filters we identify the unknown channel and evaluate the performance of each algorithm by MSE. Here, the LMS does not work and RLS has the best performance comparing to NLMS for identification of the unknown multi path channel. In repeater, the amplified signal not only transmitted to the user but also transmitted to receiver side of repeater by multipath feedback channel [1]. Therefore, in the receiver side of repeater, it will receive reference signal from base station which is ideal input of repeater and the other is feedback signal from repeaters transmitter side which is amplified. Therefore, repeater receives the interference from transmitter side. In this case, repeater system may unstable due to positive feedback. Thus, the interference cancellation system is required in order to cancel the interference signal in receiver side of repeater. In this paper, multipath channel exists in feedback channel and identify the unknown channel by adaptive filter such as LMS, NLMS and RLS. The point of this research is the fast identification of unknown channel due to rapid changing communication channel. Then, we evaluate the performance of each adaptive filter. The Channel equalizer for repeater is shown as follows

Low Frequency Compensator of Multi-variable Tele-control System

The aim of this research is to compensate the multivariable Tele-control system’s performance and preserve the stability of closed loop system. Generally in Tele-control systems, it contains with 2 time-delay elements. One is input delay and the other is feedback delay. Therefore the closed loop system’s performances become poor and lose the stability due to time-delay elements. Here by using low frequency compensator, it preserves the stability and realizes a good performance of Tele-control system.