Broadcast Engineering - April 2008 - (Page 22)

TRANSITION TO DIGITAL DIGITAL HANDBOOK DVB-SH offers a hybrid transmission model for mobile television. BY DAVID AUSTERBERRY Mobile TV of mobile use. These bands are both crowded, but higher frequencies in S-band adjacent to existing 3G services do have available bandwidth. However, S-band requires a denser transmitter network for good nterest is growing in mobile television services. However, for many countries there is no spare UHF spectrum to start transmissions. Although analog switch-off will free spectrum, that is two to ﬁve years off, depending on where you live. There is also no certainty as to what that freed spectrum will be used for. It could be for terrestrial HDTV or it could be for mobile data service, so there is much competition with a possible mobile TV operation in that spectrum. One solution to this problem is to look to different areas of the electromagnetic spectrum. Most mobile terrestrial services use UHF with L-band as an alternative. The advantage of these frequencies is that the propagation characteristics match the needs I satellite transmission for broadcast has the advantage that one transmitter can cover a large territory, whereas a terrestrial service requires a considerable investment in a transmitter network. This could be a big advantage for rural coverage S-band requires a denser without the expense of setting up a terrestrial network transmitter network for a business that has yet to for good reception be proven as a sure-ﬁre comin urban areas. mercial success. But S-band satellite transmission does not penetrate buildings in reception in urban areas. the same way as UHF. The expectaThe EU has approved the use of tion for a mobile service is that it will a section of S-band adjacent to the work in shopping malls, ofﬁces and existing 3G terrestrial services at the home. These realities have led to 2.2GHz for use with satellite or ter- the development of a hybrid satellite/ restrial transmissions. Geo-stationary terrestrial system to give much more Direct-to-mobile DVB-SH satellite Content DVB-SH signal Distribution signal Service and network head-end DVB-SH broadcast head-end Ka/Ku-band S-band TDM/ OFDM B Personal gap fillers Filler transmitters Broadcast distribution network Reception cell Mobile transmitters OFDM OFDM A C Figure 1. Overall DVB-SH system architecture 22 broadcastengineeringworld.com | April 2008 http://broadcastengineeringworld.com

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Broadcast Engineering - April 2008 Contents Editorial HD Newsrooms Wavelet Compression Mobile TV Audio Processing for HDTV, Part 1 QoE for IPTV End Users NAB Update Asset Management Advertisers Index

Broadcast Engineering - April 2008

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