Estimation and Cancellation of Doppler Shift for an OFDM Smart Antenna System

Due to users' mobility, the Doppler shift can cause the estimation error of the DOAs in antenna array systems. Therefore, the performance of the DOA based beamforming smart antenna system is degraded. In this paper, we utilize the spatial signature to estimate the Doppler shift. After estimating the Doppler shift, the effect caused by the Doppler shift is compensated and the DOAs of received signals are estimated by the spectral-smoothing algorithm and TLS-ESPRIT. In the simulation results, without the proposed estimation and compensation method of the Doppler shift, there exists estimation error of DOAs of the received signals. However, after using the proposed Doppler shift estimation method, DOAs of the received signals can be estimated. When the estimated DOAs are applied to the DOA based beamforming algorithm, the performance of the IEEE 802.16e system with smart antenna system can be better than that without Doppler estimation and compensation.