New Pilot-Symbol-Aided Estimation of Fading Channels in Mobile Communications

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Fading and co-channel interference are known as the major disturbances in mobile communications. In this research, a new pilot-symbol-aided estimation technique for estimating and compensating fading in mobile communications is explored.Among various conventional estimation and compensation methods for fading and co-channel interference, polynomial interpolation method proposed by Sampei and Sunaga (IEICE, Trans on Communications, no.1, 1989) and maximum likelihood estimation by Cavers (IEEE, Trans. VT, Nov. 1991) are well known.In this research we have extended the Caver's estimation method to use not only the known pilot symbols but also the previously estimated fading values for data symbols to extract more information on the fading channels.We have also found that the method can be further improved by utilizing, instead of the estimated fading values on data symbols, the demodulator output normalized by the decided (decoded) data symbols to estimate the fading values in the current frame.The proposed estimation methods were evaluated using both analysis and simulation. It was clarified that a BPSK system employing the proposed estimation method show a strong BER performance in the region of high signal to noise ratio under fast fading compared to that of the conventional method. Moreover, the proposed system still sustains its performance under mismatched conditions, where the conventional system degrades exhibiting error floors.