What is the principle of DMB-T terrestrial digital TV transmission system?
DMB-T adopts the time-domain synchronous orthogonal frequency division multiplexing (TDS-OFDM) multi-carrier modulation technology filled with PN sequences. This unique advanced technology organically combines the transmission of signals in the time and frequency domains. The payload is transmitted in the frequency domain, and the control signal is transmitted by spread spectrum technology in the time domain for synchronization and channel estimation,
Achieve fast codeword capture and robust synchronous tracking performance.
Technically, for the traditional OFDM modulation method that inserts strong power synchronous pilots, the effectiveness and reliability of the transmission system suffer from losses. The high protection synchronous transmission technology based on the PN sequence spread spectrum technology and the clever use of OFDM were invented. The guard interval filling technology also improves the spectrum utilization efficiency and anti-noise interference performance of the transmission system. Aiming at the shortcoming of the channel estimation iteration process of the existing transmission standard of terrestrial digital television broadcasting, a new TDS-OFDM channel estimation technology was invented to improve the mobile reception performance of the system.
In response to the fact that the European standard DVB-T using multi-carrier COFDM technology is worse than the American standard ATSC system using a single carrier 8VSB, a new error correction codec (FEC) technology was invented, which successfully avoided foreign Patent protection, obtained better system error performance than ATSC. Aiming at the problem that other standards cannot support two-way interaction and Internet expansion, an expansion design supporting the Internet has been carried out in order to adapt to the future digitization, diversification and multimedia expansion of information. On the basis of the existing digital TV radio broadcasting, the Internet business can be further expanded, Value-added services such as multicast, on-demand, and paging, and even further expand the integration, interaction, mobile, and portable of video, data, and voice. In response to the existing achievements in the digital video and audio industry, DMB-T has designed a flexible interface solution that supports the internationally accepted MPEG2-TS streaming data format and can support any type of video compression and data formats, such as MPEG-2, MPEG- 4 Wait.
DMB-T also uses a hierarchical multiframe structure that is different from existing digital TV technology standards and synchronized with natural time to support single frequency networks. The single frequency network can not only better support mobile digital TV services, but also solve the problem of blind spots that cannot be covered by a single transmitter.
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