Research On Key Technology Of Digital Television Terrestrial Broadcasting

Chinese Digital Terrestrial Television Multimedia Broadcasting (DTMB) Standard is the second modern digital mobile communication standard proposed by china and has completely independent intellectual property rights after TD-SCDMA. And it is the fourth Digital Television Terrestrial Broadcasting (DTTB) standard around the world after USA-based ATSC (Advanced Television System Committee) standard, Europe-based DVB-T (Digital Video Broadcasting-Terrestrial) standard, and Japan-based ISDB-T (Integrated Services Digital Broadcasting Terrestrial) standard. One of Its Core technology is TDS-OFDM (Time-domain Synchronous Orthogonal Frequency Division Multiplexing). In-depth study on technology around TDS-OFDM can improve the system performance, lower the receiver's cost, enhance the international competence of Chinese standards. In this dissertation, in-depth studies on carrier frequency offset estimation, channel estimation, phase noise suppression and co-channel interference in DTMB receivers are conducted. The major contributions are as follows:1) An accurate frequency offset estimation algorithm is proposed. OFDM system is very sensitive to carrier frequency offset, by exploiting the unique frame structure of DTMB, an accurate frequency offset estimation algorithm is proposed. The algorithm can break through the length limitation of training sequence, fully utilize the good self-correlation property, and has advantages of low computation complexity, high accuracy, insensitive to multipath interference. Theoretical analyses show that the algorithm has lower performance bound compared to the exist algorithms. For DTMB system , under additive white Gaussian channel, in normal signal to noise ratio (SNR) range, the normalized frequency estimation error variance is below 10-11, only 1% of the existed algorithm. Simulation results are fully in accordance with the theoretical analyses.2) An improved channel estimation algorithm suitable for TDS-OFDM system is proposed. The algorithm successfully resolves the inter-tap interference of channel impulse response caused by the imperfection of the PN sequence autocorrelation property. In the application scenario of high SNR, the algorithm can improve the Mean Square Error of channel estimation in magnitude of 10-1, improve the effective SNR of demodulator output by 5 dB, and it has been successfully implemented in a modulation analyzer.3) A CPE correction scheme, which uses the PN sequence of TDS-OFDM system signal frame and decision aided ICI eliminating scheme which uses Transmission Parameters Signaling (TPS) in TDS-OFDM signal frame, is proposed. Simulation analyses show that the proposed schemes can efficiently eliminate the ICI and CPE caused by phase noise of receiver local oscillator. And the CPE correction scheme exhibits excellent performance in strong noise and interference environment.4) Proposed an APFFT based narrow band interference suppress scheme .Due to wide coverage and co-exist with analog television broadcast, DTMB system will inevitably suffer interference of different forms, among them, the narrow band interference is the most common interference. An interference suppress scheme which combines the technology called All Phase Fast Fourier Transform (APFFT) is proposed, the scheme is suitable for both the multi-carrier and single carrier transmission mode. Simulation results show that the scheme exhibits excellent capability of suppressing strong tone interference in both modes.