Digital Television

Digital television (DTV) is the transmission of audio and video by digitally processed and multiplexed signal, in contrast to the totally analog and channel separated signals used by analog TV. It is an innovative service that represents a significant evolution in television technology since color television in the 1950s. Many countries are replacing broadcast analog television with digital television to allow other uses of the television radio spectrum. Several regions of the world are in different stages of adaptation and are implementing different broadcasting standards. There are four different digital television terrestrial broadcasting standards (DTTB) and they are: Advanced Television System Committee (ATSC) uses eight-level vestigial sideband (8 VSB) for terrestrial broadcasting. This standard has been adopted in the United States and in other countries. Digital Video Broadcasting-Terrestrial (DVB-T) uses coded orthogonal frequency-division multiplexing (C-OFDM) modulation and supports hierarchical transmission. This standard has been adapted in Europe and Australia. Terrestrial Integrated Services Digital Broadcasting (ISDB-T) is a system designed to provide good reception to fix receivers and also portable or mobile receivers. It utilizes OFDM and two-dimensional interleaving. It supports hierarchical transmission of up to three layers and uses MPEG-2 video and advanced audio coding. This standard has been adopted in Japan and most of South America. Digital Terrestrial Multimedia Broadcasting (DTMB) adopts time-domain synchronous(TDS)- OFDM technology utilizing a pseudo random signal frame to serve as the guard interval (GI) of the OFDM block and the training symbol. The DTMB standard has been adopted in the People's Republic of China (PRC), including Hong Kong and Macau.