| In TDS-OFDM (Time Domain Synchronous-Orthogonal Frequency Division Multiplexing) system, PN sequences are served as guard interval and time domain pilot signals, which could availably increase the spectrum efficiency, and provide a new subject to channel estimation. This thesis mainly investigates on a TDS-OFDM based channel estimation algorithm in combination with state digital television terrestrial broadcasting standard.First of all, under the short delay multipath channel conditions, a complex iterative computation must be utilized to improve the estimation precision in traditional algorithm, so an improved simple fast filter algorithm which utilizes the relationship between the inverse of cyclic matrix and Fourier transformation matrix is proposed, and the side lobe jamming of cyclic correlation in PN sequences could be eliminated through a simple summation operation, which could improve the calculation efficiency. Then, for the estimation of long delay multipath channel, an improved iterative PN reconstruction algorithm of channel estimation is presented, and a detection module for channel distribution is added in the iterative initialization to decrease the errors brought by noise and improve the stability and convergence rate of estimation. Furthermore, in order to increase the system performance in frequency selective fading channel, an equalization algorithm based on DFT codes is introduced, whose performance is better than traditional equalization method with zero-forcing.Finally, the design and implementation schemes of proposed channel estimation algorithm are presented, a frame head location detector together with a channel estimator based on cyclic correlation are implemented by hardware, and a low complexity scheme of removing the direct current component by summation and averaging is proposed to improve the precision of hardware realization. It is proved that the designed channel estimator could operate stably through hardware debugging. |
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