1. Inter-carrier interference cancellation in OFDM systems By: Dharamveer Meena Vinodkumar Pralia

2. Basic OFDM system Multi-carrier modulation Multiple frequency channels are orthogonal to each other.

3. OFDM modulated signal N symbols mapped to bins of IFFT. IFFT bins correspond to the orthogonal sub- carriers.

4. Baseband OFDM transceiver system

5. Drawbacks Frequency offset Local oscillator frequencies Doppler shift Result: Loss in Orthogonality Inter-carrier interference

6. Frequency offset model y(n) : received sequence  normalized frequency offset N:number of sub carriers w(n) : complex AWGN

7. Standard OFDM systems Received signal: ICI coeffiecient: Carrier to interference ratio:

8. Solutions to combat ICI Self-cancellation scheme Maximum likelihood estimation Extended Kalman Filter

9. Extended Kalman Filtering A linear approximation of a non linear system Linear : Nonlinear :

10. Offset estimation scheme State-Space Model: Recursive steps:

11. Offset correction scheme : symbol data QAM - M Restored : received data symbol distorted by frequency offset : estimated normalized frequency offset : number of subcarrier

12. References P. H. Moose, “A Technique for Orthogonal Frequency Division Multiplexing Frequency Offset Correction,” IEEE Transactions on Communications, vol. 42, no. 10, October 1994. J. Armstrong, “Analysis of new and existing methods of reducing intercarrier interference due to carrier frequency offset in OFDM,” IEEE Transactions on Communications, vol. 47, no. 3, pp. 365 – 369, March 1999. C. Muschallik, “Improving an OFDM reception using an adaptive Nyquist windowing,” IEEE Transactions on Consumer Electronics, vol. 42, no. 3, pp. 259 – 269, August 1996.

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