تخمين پارامترهاي محوشدگي كانال تخت فركانسي با استفاده از تابع مشخصه تجربي

The phenomenon of fading in wireless communication systems, caused by the reception of signals through multiple paths an‎d the resulting destructive interference is considered one of the main factors limiting the quality an‎d reliability of wireless links. Therefore, accurate modeling of the statistical characteristics of the channel an‎d estimation of its parameters are essential for system performance analysis an‎d efficient receiver design. In this thesis, the focus is on the downlink of a non-orthogonal multiple access (NOMA) system, where the user channels are modeled as frequency-flat fading channels based on the Rician distribution. Furthermore, the ambient noise is modeled by a Laplacian distribution, which is regarded as an appropriate model for multi-user interference in certain ultra-wideban‎d (UWB) systems. The main objective of this thesis is to propose an approach for the joint estimation of the line-of-sight (LOS) power, the scattered component power an‎d the Laplacian noise variance for all users with high accuracy. To this end, a method based on the empirical characteristic function (ECF) has been employed. While conventional applications of this method are typically limited to exploiting the first zeros of the characteristic function, in this thesis, nonzero points of the function are utilized to extract richer statistical information, thereby enabling the estimation of a larger number of parameters with suitable accuracy. Simulation results demonstrate that the proposed method can achieve highly accurate estimates an‎d thus may contribute to improved receiver design in the downlink an‎d enhanced performance of future wireless communication systems.

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