| Summary: | 碩士 === 大同大學 === 電機工程學系(所) === 94 === The digital TV in Taiwan adopts the transmission system of the DVB-T (Digital Video Broadcasting-Terrestrial). Originally, we can only broadcast a simulation TV program in 6MHz channel, but now, with the TV signal had been “digital compressed”, we can broadcast three or more Standard TV in one channel at the same time.
Because of the bit compressed technology progresses constantly, the TV and broadcast are all overall digitization. Although the bit compressed technology can save the transmission bandwidth and improve the utilization ratio of the channel, it paid a huge cost in become very sensitive in interference of transmission. Generally speaking, the higher the compression ratio is, the weaker the resistance of transmission interference it had in digital TV. Therefore, we need to add the channel code to get better transmission characteristic, although it may reduce the loading capacity of transmission.
To solve this problem, DVB-T uses the code of COFDM. It can improve the dependability of the transmission system, and the error correcting system put forward the purpose. However, the revision ability is limited in any error correcting system. In signal transmitting, when the digital error is bigger than the error-correcting ability, it will be unable to revise the error, may cause more serious error.
Therefore, DVB-T adopts two grades of error-correcting methods to improve the error-correcting ability. In this paper, it will set up the DVB-T system in the simulation environment of Simulink, and we can analysis and compare the efficiency of error correcting system.
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