Sharif Digital Repository

The Per Tone equalization algorithm is a novel discrete multitone (DMT) equalization method with practical applications in subscriber digital loop systems. Unlike time domain DMT equalizers (TEQ), which equalize all DMT tones in a combined fashion, the Per Tone equalizer equalizes each tone separately. In this paper, the performance and complexity of this technique is investigated and compared with that of other TEQs. Furthermore, the behavior of this technique in different simulation conditions, such as over different standard CSA loops and in the presence of additive white Gaussian noise with variable power spectral density level and near end crosstalk (NEXT), is studied and compared with... 

Herein, we propose a method based on the existing second-order blind identification of underdetermined mixtures technique for identifying the modal characteristics - namely, natural frequencies, damping ratio, and real-valued partial mode shapes of all contributing modes - of structures with a limited number of sensors from recorded free/ambient vibration data. In the second-order blind identification approach, second-order statistics of recorded signals are used to recover modal coordinates and mode shapes. Conventional versions of this approach require the number of sensors to be equal to or greater than the number of active modes. In the present study, we first employ a parallel factor... 

Long-span bridges usually experience different input excitations at their ground supports that emanate from differences in wave arrival times, and soil conditions, as well as loss of coherency in arriving waves. These spatial variations can drastically influence the dynamic response; hence, this phenomenon must be considered in any vibration-based identification method. There are numerous Multi-Input Multi-Output (MIMO) identification techniques that may be applied to data recorded at long-span bridges that experience spatial variations in their input motions. However, inertial soil-structure interaction effects severely reduce the accuracy of these techniques because the actual Foundation... 

This paper presents an optimum pre-filter for ICA based multi-input multi-output OFDM system. In our former work, we presented a pre-filter solution for multiuser reconstruction in ICA based MIMO-OFDM systems [1,2]. Here, based on the structure of the system and former pre-filter solution, an optimization problem has been designed to give us the optimum pre-filter. The designed problem is based on minimization of the estimation error of ambiguities inherent to ICA in reconstruction of the data after separation. The optimization problem is mathematically solved and a set of optimized coefficients are obtained. Among the obtained set as optimum coefficients, optimum coefficients are acquired... 

This paper presents an Optimum pre-filter for ICA based mulit-input multi-output OFDM System. In our former work, we presented a pre-filter solution for multiuser reconstruction in ICA based MIMO-OFDM systems [1], [2]. Here, based on the structure of the system and former prefilter solution, an optimization problem has been designed to give us the optimum pre-filter. The designed problem is based on minimization of the estimation error of ambiguities inherent to ICA in reconstruction of the data after separation. The optimization problem is mathematically solved and a set of optimized coefficients are obtained. Among the obtained set as optimum coefficients, optimum coefficients are acquired... 

This paper concerns the maximum-likelihood channel estimation for MIMO systems with orthogonal space-time block codes when the finite alphabet constraint of the signal constellation is relaxed. We study the channel coefficients estimation subspace generated by this method. We provide an algebraic characterisation of this subspace which turns the optimization problem into a purely algebraic one and more importantly, leads to several interesting analytical proofs. We prove that with probability one, the dimension of the estimation subspace for the channel coefficients is deterministic and it decreases by increasing the number of receive antennas up to a certain critical number of receive... 

Surrounding soil can drastically influence the dynamic response of buildings during strong ground shaking. Soil's flexibility decreases the natural frequencies of the system; and in most cases, soil provides additional damping due to material hysteresis and radiation. The additional damping forces, which are in non-classical form, render the mode shapes of the soil-structure system complex-valued. The response of a soil-foundation system can be compactly represented through impedance functions that have real and imaginary parts representing the stiffness and damping of the system, respectively. These impedance functions are frequency-dependent, and their determination for different...