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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

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Outline

Introduction System Description Proposed Scheme Simulation Results Conclusion

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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.

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System Description

The nth received sample has the standard form:

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System Description

Schmidl’s Method

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System Description

Minn’s Method

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System Description

Park’s Method

D is designed to be symmetric with the conjugate of C.

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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

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Proposed Scheme

The form of the designed training symbol

in time domain is as follows:

B. Time Synchronization

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Proposed Scheme

Comparison of the timing metric of estimators

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Proposed Scheme

The fractional frequency offset can be estimated by ML estimator using the redundant information contained within the cyclic prefix:

C. Frequency Synchronization

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Proposed Scheme

Coarse estimate by minimum energy detection

Fine estimate by partial correlation

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Proposed Scheme

COMPARISON OF THE FREQUENCY OFFSET ESTIMATION RANGE

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Simulation Results

Channel impulse response of the multipath fading channel

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Simulation Results

MSE of the timing offset estimation in multipath fading channels

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Simulation Results

Mean of the frequency offset estimation in multipath fading channels

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Simulation Results

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Simulation Results

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Simulation Results

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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.

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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

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Thanks for your attention