COMPARISON OF SOME METHODS INCLUDIDNG USE OF CODING FOR REDUTION OF ICI OFDM CHANNELES مقاله

نویسنده: A. R. ZOLGHADRASLI ؛ M. A. MASNADI ؛ B. AMIN SHAH ؛ M. H. GHAMAT ؛

International Journal Of Information Science And Management July & December 2006, Volume 4 - Number 2 ISC (‎14 صفحه - از 1 تا 14 )

کلیدواژه ها: Coding OFDM Maximum likelihood Extended Kalman filter bit error rate Intercarrier Interference BPSK Modulation Self Cancellation Modify Self Cancellation AWGN CFO PICR

چکیده:

One of the limitations of orthogonal frequency division Multiplexing (OFDM) in many applications is its sensitivity to frequency shifis, errors normally referred to as carrier frequency offset (CFO). Although, this small offset is negligible in conventional single carrier communication systems, it is a severe problem in the OFDM systems. Because, the carriers in OFDM are inherently closely spaced in frequency, the tolerable frequency offset becomes a very small fraction of the channel bandwidth. Besides, for OFDM communication systems, the frequency offset in mobile radio channels distorts the orthogonality between subcarriers, resulting in intercarrier interference (ICI). In this paper, we analyze and compare the performance of some already existing methods for reducing ICI with new ICI cancellation schemes by simulation. Also the advantage of using a coding scheme is shown.

خلاصه ماشینی:

Besides, for OFDM communication systems, the frequency offset in mobile radio channels distorts the orthogonality between subcarriers, resulting in intercarrier interference (ICI). Abstract - Keywords - Intercarrier Interference, OFDM, BPSK Modulation, Extended Kalman Filter, Bit Error Rate, Self Cancellation, Modify Self Cancellation, Maximum Likelihood, Coding, AWGN, CFO, PICR INTRODUCTION Wireless communications is an emerging field, which has witnessed enormous growth in the last several years. (View the image of this page) Where ni is a complex Gaussian noise sample (with its real and imaginary components being independent and identically distributed with variance 2) The second term in (2) is the ICI term attributable to the carrier frequency offset (CFO). It was shown by Moose that CFO (Carrier Frequency Offset) can be estimated using Maximum likelihood (ML) algorithm and is equal to [4]: Iranian Journal of Information Science & Technology, Volume 4, Number 2 July'/December. SIMULATION (View the image of this page) Performance of four ICI reduction algorithms namely ICI self cancellation, Modified ICI self cancellation, Maximum likelihood offset estimation and Extended Kalman filter offset estimation were evaluated and compared with an ordinary OFDM system. The simulator can be used to compare the above algorithms in terms of BER, for any value of alphabet size (M), Number of subcarriers (N), frequency offset (e) and type of modulation (QAM, PSK). lt is seen that for lower values of frequency offset BER of extended kalman filter was least followed by maximum likelihood method. It is seen that for both lower as well as higher values of frequency, offset extended kalman filter gives best results followed by maximum likelihood method.

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