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As Dar goes digital come December

1st December 2012
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Editorial cartoon

Come December 31st we are all going digital, or so we learn. For the average consumer, the switch to digital TV broadcasts only means better pictures and sound quality. A digital signal doesn't suffer from the same degradation as an analogue signal.

Do we remember the days when our favorite show would drift in and out of audio and visual "snow?" With digital broadcasts, that snow is permanently melted.

Digital signals also mean that movies broadcast over the air can now appear in their original widescreen format instead of being cut down to fit the smaller television screen – and you have more options
Digital television (DTV) is the transmission of audio and video by digitally processed and multiplexed signal, in contrast to the totally analogue and channel separated signals used by analogue 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 analogue 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 include:

Advanced Television System Committee (ATSC) which 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; and  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.

A digital signal can carry more information than an analogue signal, which means that more sound and video options can travel to your TV set; a TV station signal, for instance, could offer multiple programming choices (called multicasting) as well as interactive capabilities – to transmit up to three standard-definition (SDTV) transmissions; that is three different shows on one digital channel.

The most important reason for switching to a digital signal is to free up valuable portions of the broadcast spectrum, which could then be used for other purposes -- such as advanced wireless services and for public and safety services. Plus, networks and TV stations can stop spending the time, money, effort, and electricity doing double duty and transmitting both analogue and digital signals.

The challenge before Tanzania is that we badly need this quality service – and the catchphrase is how we can possibly celebrate “Digital Tanzania” with our backward infrastructure.

SOURCE: THE GUARDIAN
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