Broadcast Engineering - April 2008 - (Page 24)

TRANSITION TO DIGITAL DIGITAL HANDBOOK reliable delivery of content to mobile receivers. The cost of setting up a terrestrial mobile service is not the only barrier to success. Experience has shown that the public must have a wide range of handsets to choose from, especially the tier-one suppliers. This means that receiver chips and antenna designs must be attractive to the massmarket handset manufacturer. Combine opportunity with a business case, and the service is possible. Add standardization, and it becomes a real possibility. In 2007, the DVB approved a standard for a hybrid satellite-mobile service, designated DVB-SH. DVB-SH is primarily designed to deliver IP-based multimedia, much like DVB-H. This would include broadcast TV and radio, plus data for EPGs, news services and interactive services. DVB-SH is based on DVB-H, but adds enhancements to improve the robustness of the signal. The same time-slicing is used to conserve battery power. The primary modulation is orthogonal frequency division multiplex (OFDM), but a second scheme, time division multiplex (TDM), which is partially derived from DVB-S2, is added as an option for the satellite downlink. The provision of two options allows more ﬂexibility for optimization of the satellite performance. If a single DVB-SH multiplex is used per HPA in the satellite, then TDM allows the optimum HPA performance by operating close to saturation. If several multiplexes are used per HPA, then the ampliﬁer must be backed off. In this case either, TDM or OFDM can be used with little difference in performance. A new FEC called 3GPP turbo code, plus a highly ﬂexible channel interleaver to address typical satellite propagation impairments like fading, is used. Tall buildings obscure signals, as do bridges, and a mobile service should be designed to cope with short interruptions from such shading of the signal. The interleaving provides for time diversity from about 100ms (for terrestrial) to several seconds (for satellite) depending on the targeted service level. Transmission and distribution The hybrid model uses satellite as the primary means of transmission. In urban areas, gap ﬁllers can use dedicated circuits or repeat the satellite transmissions. These repeaters could well be co-sited with 3G transmitters, especially as they share the 2.2GHz band. The gap ﬁllers can be conﬁgured as an SFN along with the satellite transmissions. Both QPSK and 16-QAM are supported in the defining the future of HD CamPac 2 CM TX7 NCVT7 CR7 NCDR Portable/ENG Microwave Link Products � � the world's most advanced � SD and/or HD video formats Variable COFDM bandwidths from 5 to 16 MHz Integrated multiple modulation modes: COFDM/VSB/FM Integrated spectrum viewer for all receivers Single band, dual band or tri-band frequency options Intuitive ease of operation Nucomm, Inc. European Regional Office +44 1449 736033 � � � Nucomm, Inc. US Headquarters +1 908.852.3700 Nucomm, Inc. I www.nucomm.com 24 broadcastengineeringworld.com | April 2008 http://broadcastengineeringworld.com

Table of Contents Feed for the Digital Edition of Broadcast Engineering - April 2008

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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