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DVB-H (Digital Video Broadcasting - Handheld) is one of three prevalent mobile TV formats. It is a technical specification for bringing broadcast services to mobile handsets. DVB-H was formally adopted as ETSI standard EN 302 304 in November 2004. The DVB-H specification (EN 302 304) can be downloaded from the official DVB-H website.〔(DVB-H : Global Mobile TV )〕 From March 2008, DVB-H is officially endorsed by the European Union as the "preferred technology for terrestrial mobile broadcasting".〔(Rapid - Press Releases - EUROPA )〕〔(Commission opens Single Market for Mobile TV - Europe's Information Society Newsroom )〕〔(eCommunications: Site re-launch | Europa - Information Society )〕〔(EU endorses Nokia-backed DVB-H mobile broadcasting standard - International Herald Tribune )〕 The major competitors of this technology are Qualcomm's MediaFLO system, the 3G cellular system based MBMS mobile-TV standard, and the ATSC-M/H format in the U.S. DVB-SH (Satellite to Handhelds) now and DVB-NGH (Next Generation Handheld) in the future are possible enhancements to DVB-H, providing improved spectral efficiency and better modulation flexibility. DVB-H has been a commercial failure, and the service is no longer on-air. Finland was the last country to switch-off its signals in March 2012. ==Technical explanation== DVB-H technology is a superset of the successful DVB-T (Digital Video Broadcasting - Terrestrial) system for digital terrestrial television, with additional features to meet the specific requirements of handheld, battery-powered receivers. In 2002 four main requirements of the DVB-H system were agreed: broadcast services for portable and mobile usage with 'acceptable quality'; a typical user environment, and so geographical coverage, as mobile radio; access to service while moving in a vehicle at high speed (as well as imperceptible handover when moving from one cell to another); and as much compatibility with existing digital terrestrial television (DVB-T), to allow sharing of network and transmission equipment.〔Goggin, Gerard. Cell Phone Culture Mobile Technology in Everyday Life. New York: Routledge, 2006. Print.〕 DVB-H can offer a downstream channel at high data rates which can be used as standalone or as an enhancement of mobile telecommunication networks which many typical handheld terminals are able to access anyway. Time slicing technology is employed to reduce power consumption for small handheld terminals. IP datagrams are transmitted as data bursts in small time slots. Each burst may contain up to two megabits of data (including parity bits). There are 64 parity bits for each 191 data bits, protected by Reed-Solomon codes. The front end of the receiver switches on only for the time interval when the data burst of a selected service is on air. Within this short period of time a high data rate is received which can be stored in a buffer. This buffer can either store the downloaded applications or playout live streams. The achievable power saving depends on the relation of the on/off-time. If there are approximately ten or more bursted services in a DVB-H stream, the rate of the power saving for the front end could be up to 90%. DVB-H is a technical system which was carefully tested by the DVB-H Validation Task Force in the course of 2004 (see ETSI Technical Report TR 102 401). DVB-SH improved radio performances and can be seen as an evolution of DVB-H. DVB-H is designed to work in the following bands: *VHF-III (170-230 MHz, or a portion of it) *UHF-IV/V (470-862 MHz, or a portion of it) *L (1.452-1.492 GHz) DVB-SH now and DVB-NGH in the near future are expected to expand the supported bands. DVB-H can coexist with DVB-T in the same multiplex. 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「DVB-H」の詳細全文を読む スポンサード リンク
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