1. 1 A Novel Time and Frequency Synchronization Scheme for OFDM Systems Ching-Yu Wang Graduate Institute of Communication Engineering National Chi Nan University 12 / 25 / 2008

2. 2 Outline Introduction System Description Proposed Scheme Simulation Results Conclusion

3. 3 Introduction Schmidl’s method has a plateau which causes a large variance in the timing offset estimation. Minn’s method performs well, but its estimation variance is quite large in ISI channels. Park produces an even sharper timing metric than Schmidl’s and Minn’s, but its timing metric has two large sidelobes which will affect the timing performance.

4. 4 System Description The nth received sample has the standard form:

5. 5 System Description Schmidl’s Method

6. 6 System Description Minn’s Method

7. 7 System Description Park’s Method D is designed to be symmetric with the conjugate of C.

8. 8 Proposed Scheme The samples of the new training symbol in frequency domain are designed to be of the form: and the corresponding time-domain complex baseband training symbol samples are A. Proposed Training Symbol

9. 9 Proposed Scheme The form of the designed training symbol in time domain is as follows: B. Time Synchronization

10. 10 Proposed Scheme Comparison of the timing metric of estimators

11. 11 Proposed Scheme The fractional frequency offset can be estimated by ML estimator using the redundant information contained within the cyclic prefix: C. Frequency Synchronization

12. 12 Proposed Scheme Coarse estimate by minimum energy detection Fine estimate by partial correlation

13. 13 Proposed Scheme COMPARISON OF THE FREQUENCY OFFSET ESTIMATION RANGE

14. 14 Simulation Results Channel impulse response of the multipath fading channel

15. 15 Simulation Results MSE of the timing offset estimation in multipath fading channels

16. 16 Simulation Results Mean of the frequency offset estimation in multipath fading channels

17. 17 Simulation Results

18. 18 Simulation Results

19. 19 Simulation Results

20. 20 Conclusion A new training symbol is designed and a simple time and frequency synchronization scheme is proposed in this paper. The scheme gives very accurate estimates of symbol timing and carrier frequency offset and provides a very wide acquisition range for the carrier frequency offset.

21. 21 References G. Yi, L. Gang, G. Jianhua, “A novel time and frequency synchronization scheme for OFDM systems,” IEEE Transactions on Consumer Electronics, Vol. 54, pp.321 - 325, May. 2008

22. 22 Thanks for your attention