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Frequency Drift in Repeated Transmission Schemes

Frequency Drift in Repeated Transmission Schemes. Date: 2012-01-16. Authors:. Abstract.

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Frequency Drift in Repeated Transmission Schemes

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  1. Frequency Driftin Repeated Transmission Schemes Date:2012-01-16 Authors: Heejung Yu, ETRI

  2. Abstract In this submission, a problem of frequency drift in a time-domain repetition scheme is discussed. By providing a possible tracking scheme of residual carrier frequency offset, we can expect that frequency drift may not be a significant problem in repetition over OFDM symbols. Heejung Yu, ETRI

  3. In Nov. 2011, we presented about several repetition schemes. • frequency domain repetition within one OFDM symbol • time domain repetition over two consecutive OFDM symbols with and without permutation of subcarriers • A comment on frequency drift in time-domain repetition was received. • Therefore, we introduce a possible solution to this problem. Background Heejung Yu, ETRI

  4. Due to both the lower operating SNR and 10 longer OFDM symbol duration, the performance oflowest MSC with repetition will be severely deteriorated by frequency drift. Especially in atime-domain repetition, this effect is more significant since two OFDM symbols are combined. To overcome this problem, the more accurate estimation of residual carrier frequency offset (CFO) is required. Problem Statement Heejung Yu, ETRI

  5. Symbol structure of 2x permuted repetition in frequency domain Signal Model Subcarrier index Subcarrier index Channel Frequency drift OFDM symbol index (time index) OFDM symbol index (time index) Heejung Yu, ETRI

  6. Due to the repetition property, we can obtain more accurate estimate of residual CFO. • After equalizing the frequency channels, we have • We have the estimate of residual CFO Residual CFO Estimation (1) Subcarrier index OFDM symbol index (time index) Heejung Yu, ETRI

  7. As shown in the previous slide, we can use all subcarriers (including pilot-carriers and data-carriers) to estimate the residual CFO. Therefore, we obtain more accurate estimates of CFO. By tracking residual CFO with these estimates, we can minimize the performance loss caused by frequency drift. Residual CFO Estimation (2) Heejung Yu, ETRI

  8. The comment on the problem of frequency drift in time-domain repetition is reviewed. By using the residual CFO estimation scheme, the performance loss due to frequency drift can be reduced. The simulation results about this issue is in preparation. Conclusions Heejung Yu, ETRI

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