IJE TRANSACTIONS A: Basics Vol. 30, No. 10 (October 2017) 1517-1525    Article in Press

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E. Hari Krishna, K. Sivnai and K. Ashoka Reddy
( Received: June 07, 2017 – Accepted in Revised Form: July 07, 2017 )

Abstract    This paper presents an empirical mode decomposition (EMD) based adaptive filter (AF) for channel estimation in OFDM system. In this method, length of channel impulse response (CIR) is first approximated using Akaike information criterion (AIC). Then, CIR is estimated using adaptive filter with EMD decomposed IMF of the received OFDM symbol. The correlation and kurtosis measures are used to select the useful IMF component from among available IMFs. Conventional AF uses random initial weight vector. The novelty of the proposed method is that it uses decimated version of one of the decomposed IMFs of received OFDM symbol as initial weight vector. This makes the proposed EMD based AF method converge to minimum mean square error (MMSE) in less number of iterations resulting in almost 50% saving of computations. The simulation studies in terms of bit error rate (BER) and mean square error (MSE) calculations established the efficacy of proposed method; and comparative studies under different modulation schemes and fading conditions revealed improved performance.


Keywords    OFDM, Multi carrier channel estimation, Adaptive filtering, Empirical Mode Decomposition (EMD), Multipath fading channel


چکیده    این مقاله یک فیلتر انطباق مبتنی بر تجزیه حالت تجربی (EMD) را برای تخمین کانال در سیستم OFDM ارائه می دهد. در این روش، طول پاسخ ضربان کانال (CIR) ابتدا با استفاده از معیار اطلاعات Akaike (AIC) تقریب زده می­شود. سپس CIR با استفاده از فیلتر انطباق با EMD تجزیه شده از IMF از نماد OFDM دریافت شده تخمین زده می­شود. برای ارزیابی مولفه­های IMF از میان IMFهای موجود استفاده از اقدامات همبستگی و kurtosis استفاده می شود. AF متعارف از بردار وزن اولیه تصادفی استفاده می کند. نوآوری روش پیشنهادی این است که از نسخه خراب شده یکی از IMFهای تجزیه شده از نماد OFDM دریافت شده به عنوان بردار وزن اولیه استفاده می­کند. این باعث می شود روش AF مبتنی بر EMD با حداقل تعداد خطای مربع (MMSE) در تعداد کمی از تکرارها منجر به صرفه جویی در حدود 50٪ زمان محاسبه شود. مطالعات شبیه­سازی با استفاده از محاسبات خطای بیت (BER) و میانگین مربعات خطا (MSE)، اثربخشی روش پیشنهاد شده را تأیید کرد و مطالعات تطبیقی تحت برنامه های مختلف مدولاسیون و شرایط محو شوندگی عملکرد را بهبود بخشید.


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