| Summary: | 碩士 === 國立東華大學 === 電機工程學系 === 96 === As the physics of wave propagation tells us, the mobility of the user would cause the Doppler frequency offset. For the system based on OFDM, frequency shift may affect directions-of-arrival (DOA) from the sighals, so that the signal cannot be received accurately.
In this thesis, we use WirelessMAN-OFDM PHY from IEEE 802.16e standard as system stages. In the mobile channel, the received antennas will be multiplied by the received weight and the transmitted antennas will be multiplied by the transmitted weight fed back from the channel information in MIMO system. The channel matrix will be obtained by spatial signature, and the Doppler frequency shift can be estimated accordingly. In MIMO system, we use the autocorrelation matrix to get the channel matrix, and we used the subspace smoothing to prove the full rank of the channel matrix. Then the high resolution DOA estimation algorithms, such TLS-ESPRIT, can be used to accurately estimate the DOAs of received signals. Finally, we can use the proposech algorithm to estimate frequency shift and we can compensate for frequency shift, so that the system becomes better.
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