channel estimation

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Reducing ICI Effect in OFDM System Using Low-Complexity Kalman Filter Based on Comb-Type Pilots Arrangement

Journal Title, Volume, Page: 
International Journal of Communication Systems, 24:53–61
Year of Publication: 
2011
Authors: 
Allam Mousa
Electrical Engineering Department, An Najah University, Nablus
Current Affiliation: 
Department Of Electrical Engineering, Faculty Of Engineering, An-Najah National University, Nablus, Palestine
Hala Mahmoud
Electronics Engineering Department, Al-Quds University, Jerusalem
Preferred Abstract (Original): 
In OFDM systems, time-varying channels destroy orthogonality between subcarriers causing Inter-Carrier Interference. To reduce this effect, a Kalman filter, as a benchmark, is used for channel estimation, based on comb-type pilot arrangements of the OFDM system. An advantage of comb-type pilot arrangements in channel estimation is the ability to track the variation of the channel caused by Doppler frequency. Kalman method has been proposed to estimate the channel frequency response (CFR) at the pilot locations, then CFR, at data subchannels, is obtained by means of interpolation between estimates at pilot locations. The low-complexity Kalman method is introduced to reduce the complexity of the system while achieving the same BER/SNR. Different types of interpolations have been also compared such as Low-pass, Spline-cubic and Linear interpolation methods. The BER/SNR performance of BPSK modulation schemes are considered for time varying Rayleigh fading channels. Our results has shown that the low-complexity Kalman estimation, used with the pilot arrangement and a suitable interpolation method, gives almost the same performance as that of the Kalman method specially for low SNR values and hence the effect of Doppler shift effect is controlled.
Allam's picture

Channel Estimation Based In Comb-Type Pilots Arrangement For OFDM System Over Time Varying Channel

Journal Title, Volume, Page: 
Journal of Networks, Vol. 5, No. 7, July 2010
Year of Publication: 
2010
Authors: 
Allam S. Mousa
Department of Electrical Engineering, Faculty of Engineering, An-Najah National University, Nablus, Palestine
Current Affiliation: 
Department of Electrical Engineering, Faculty of Engineering, An-Najah National University, Nablus, Palestine
Hala M. Mahmoud
Department of Electronics Engineering, Al-Quds University, Jerusalem, Palestine
Rashid Saleem
University of Manchester, School of Electrical and Electronic Engineering, UK
Preferred Abstract (Original): 
Orthogonal Frequency Division Multiplexing (OFDM) has been recently applied widely in wireless communication systems, due to its high data rate, transmission capability with high bandwidth, efficiency and its robustness to multipath delay .Channel estimation is an essential problem in OFDM system. Pilot-aided channel estimation has been used; a good choice of the pilot pattern should match the channel behavior both in time and frequency domains. We explored comb pilot arrangements. The advantage for comb type pilots arrangement in channel estimation is the ability to track the variation of the channel caused by doppler frequency, it is observed that the doppler effect can be reduced, and so this will increase the system mobility. Kalman and Least Square (LS) estimators have been proposed to estimate the Channel Frequency Response (CFR) at the pilots location, then CFR at data sub channels are obtained by mean of interpolation between estimates at pilot locations. Different types of interpolations have been used such as; low pass interpolation; spline cubic interpolation and linear interpolation. Kalman estimation has better performance than LS estimation. The estimators perform about the same for SNR lower than 10 dB. The performances of all schemes have been compared by finding Bit Error Rate (BER), where BPSK modulation scheme was used.
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