歐規數位無線電視錯誤修正系統之模擬及效能分析

我國數位電視採用DVB-T(Digital Video Broadcasting-Terrestrial) 歐洲規格的發射系統，在指配給電視台的一個6MHz 頻道中，原本只能播出一個類比電視節目，但電視訊號經「數位壓縮」處理後，一個頻道可以同時播出三個或更多的標準畫質電視SDTV（Standard TV）節目。由於位元率壓縮技術不斷的進步，雖然可以大大的節省傳輸頻寬，提高頻道的利用率，但是也付出了一個相當大的代價，就是對於傳輸的干擾變的十分的敏感。一般而論，壓縮倍數越高，數位電視對傳輸干擾的抵抗能力越弱，因此在傳輸過程中需加上頻道編碼，雖然會降低傳輸負載容量，但可求得較佳之傳輸特性。而為了解決此問題，DVB-T使用COFDM之編碼，近一步的提高傳輸系統的可靠性，錯誤修正編碼也就是為了這個目的所提出來的。但是任何的錯誤修正系統的修正能力都是有限的，在傳輸信號中造成的位元錯誤超過錯誤修正能力時，錯誤修正系統將無法修正錯誤，並可能會造成更嚴重的錯誤產生。因此DVB-T採用了兩級的錯誤修正方法來近一步提高錯誤修正的能力。而本篇論文將在Simulink的模擬環境中建立一個DVB-T的系統，並針對其錯誤修正系統的效能來做分析與比較。

關鍵字

正交分頻多工；數位電視

並列摘要

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.

並列關鍵字

OFDM ； DVB-T

參考文獻

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[5] ETSI, "Radio Broadcasting Systems: Digital Audio Broadcasting to Mobile, Portable and Fixed Receivers," European Telecommunication Standard, ETS 300-401, Feb. 1995.

[8] Reimers, U., "DVB-T: The COFDM-Based System for Terrestrial Television, "Electronics and Communication Engineering Journal, Vol. 9, No. 1, pp. 28-32, Feb. 1997.

[9] Gallager, R. G., Information Theory and Reliable Communication, John Wiley and Sons, New York, 1968.

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歐規數位無線電視錯誤修正系統之模擬及效能分析

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