|
The digital dividend refers to the radio spectrum which is released in the process of digital television transition. When television broadcasters switch from analog TV to digital-only platforms, part of the electromagnetic spectrum that has been used for broadcasting will be freed-up because digital television needs less spectrum than analog television. One reason is that new digital video compression technology can transmit numerous digital subchannels using the same amount of spectrum used to transmit one analogue TV channel. However, the primary reason is that digital transmissions require much less of a guard band on either side, since they are not nearly as prone to RF interference from adjacent channels. Because of this, there is no longer any need to leave empty channels to protect stations from each other, in turn allowing stations to be repacked into fewer channels, leaving more contiguous spectrum to be allocated for other wireless services. The digital dividend usually locates at frequency bands from 174 to 230 MHz (VHF) and from 470 to 862 MHz (UHF). However, the location and size of digital dividend vary among countries due to the factors including geographical position and penetration of satellite/cable services. As a result of the technological transition, a significant number of governments are now planning for or allocating their digital dividends. For examples, the United States completed its transition on 12 June 2009 and auctioned the spectrum. Meanwhile, Australia is still planning for it. ==Potential uses== In countries where the digital television transition has not yet finished, over-the-air broadcasting services are still using radio-frequency spectrum in what is known as the Very High Frequency (VHF) and Ultra High Frequency (UHF) bands. After the completion of digital transition, part of this spectrum will be released as digital dividend to provide a range of new communication services. Proposed utilization of the released spectrum includes: * Digital Terrestrial TV * Advanced Mobile Services * Broadcast Mobile TV * Commercial Wireless Broadband services, both to fixed locations and mobile devices * Wireless Broadband services for public safety and disaster relief (PPDR) * Services ancillary to broadcasting and programming (SAB/SAP) Analog television spectrum in the UHF bands is valuable to potential purchasers because of its ability to carry signals over long distances, penetrate buildings and carry large amounts of data. Lots of countries are in favour of using a part of the digital dividend for electronic communications services, such as mobile communications and wireless broadband. These new services would utilize the upper part of the UHF band (790-862 MHz). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Digital dividend after digital television transition」の詳細全文を読む スポンサード リンク
|