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Title:	An improved interpolation method for channel estimation in an orthogonal frequency division multiplexing (OFDM) system using pilot signals
Authors:	Ahmed Noori Hummadi (P43836)
Supervisor:	Mahamod Bin Ismail, Professor Dr.
Keywords:	Improved interpolation method Channel estimation Orthogonal frequency division multiplexing system OFDM system Using pilot signals Orthogonal frequency division multiplexing
Issue Date:	10-May-2011
Description:	Orthogonal Frequency Division Multiplexing (OFDM) system can achieve high data rates in mobile environment due to its robustness against the Inter Symbol Interference (ISI). Likewise, development of efficient receiver with proper channel estimation technique is crucial to ease the prediction of the received signal. Pilot symbol assisted modulation introduced to achieve reliable channel estimation through transmitting pilot signals along with in OFDM symbol. Moreover, interpolation method developed to estimate the channel samples and eliminates the effect of the fading channel from the received signals. However, most of the interpolation techniques such as Linear, Cubic and Spline Cubic interpolation are irresistible against the noise while the conventional interpolation is not resilience. The objective of this work is to propose a new improved interpolation technique which is more reliable and efficient for channel estimation in OFDM system based on pilot signal under fast varying and noisy channels. The proposed interpolation is much simpler than other technique, such as Linear, Second Order Modulation, Spline, Time domain, and Low-pass interpolation; where it depends on two parameters which are the mean and variance of two adjacent pilot signals. Furthermore, this type of interpolation can be modified to give more accurate estimation for the channel depending on two modification factors (β and ξ). The mathematical formulations have been derived based on linear interpolation technique and then validated using simulations. The Mean Square Error (MSE) performance of the interpolation technique is then compared with other five types of interpolation under Rayleigh fading channel using comb type channel estimation. Simulations show that the proposed interpolation technique able to estimate the channel much better than other interpolation types for Signal to Noise Ratio (SNR) from 1 dB to 8 dB at MSE equal to 10-3 and as a result it is much robust against noise which reduces the accuracy of the estimated channel. Furthermore, the channel estimation is then used to examine the effect of pilot estimation using different technique of estimation such as Least Square Error (LSE), Minimum Mean Square Error (MMSE) and Wavelet De-noising. It is shown that pilot estimation give superior MSE performance in channel estimation by about 20 dB at low SNR. Simulation also shows that SNR performance improved up to 10 dB comparing to other type of interpolation at BER equal to 10-3. Finally, the proposed method also performed well in the estimation of the channel over different Doppler frequencies and achieves higher OFDM system performances.,PhD
Pages:	130
Call Number:	TK5103.484 .H836 2011
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Engineering and Built Environment / Fakulti Kejuruteraan dan Alam Bina

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