DVB-H delivers mobile TV

Nokia is an active supporter of the development of mobile TV technology based on the DVB-H standard. In this white paper, the company discusses the relative merits of the technology as a content delivery platform.

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By  Administrator Published  October 29, 2007

Over the last 10 years, digital technology has encouraged rapid growth in the personal consumption of media. As part of this trend new digital broadcast technologies have been developed that enable viewers to watch television-like services on their mobile devices.

Facilitating these applications is the Digital Video Broadcast - Handheld (DVB-H) standard, which is based upon the well-known DVB-T digital TV standard. DVB-T has been used extensively worldwide to facilitate digital TV services, and has the support of more than 270 companies in 35 countries which are part of the DVB Project.

DVB-H provides a range of benefits, including low battery consumption and robust functionality, even in difficult reception environments; it enables cost-effective implementation of broadcast networks; has the bandwidth capacity for rich audiovisual content, appealing to content companies and advertisers; it uses the UHF spectrum which is reserved for broadcast use; it is also an open standard which will lower costs and offer more choice.

From a technical and financial point of view, it is feasible to build DVB-H networks with similar coverage as mobile telephone networks. In addition, DVB-H devices can benefit from the technology already available in mobile terminals. Consequently, it makes sense to integrate DVB-H reception with mobile telephones to benefit from access to mobile telecom and broadcast networks.

The DVB-H physical layer specification is the same as that used by DVB-T, and reuses existing DVB concepts for service discovery and data broadcasting. Some optional features have been added to the DVB-H physical layer to improve system flexibility (additional 5Mhz channel bandwidth and 4K mode). While DVB-T is primarily designed for rooftop antenna reception, a DVB-H network is designed for portable reception with handheld devices even indoors. This leads to a different network topology in case of DVB-T and DVB-H. Good quality indoor reception with a small antenna requires a dense network topology, i.e. more transmitters than when receiving with large rooftop antennas.

Typically, in an urban area one DVB-H network cell (Single Frequency Network, SFN) would utilise three to five low-power (a few kilowatts) transmitters and cover an area of 15 kilometres (10 miles) in radius. Such a network will cost approximately $1.4 million.

DVB-H uses a technique called time-slicing. Using this scheme, the data of a DVB-H service is not broadcast continuously but is bundled in ‘bursts' at a high data rate. To illustrate, during one tenth of a second, data is sent to the receiver to play out the programme for the next second. This means that the battery can be switched off between the data bursts i.e. about 90% of the time, without the user noticing. This is a big advantage considering the typically limited battery power available in a mobile phone. With standard batteries, a viewing time of roughly four hours can be achieved.

As handheld devices have small antennae and require reception under varying signal conditions, a robust transmission system with solid error protection is needed. To better match the handheld environment, DVB-H offers improved transmission robustness through the use of an additional level of forward error correction (FEC) at the multi protocol encapsulation (MPE) layer. This combined with flexibility to use 2K, 4K or 8K radio mode enables better Doppler performance meaning improved mobile signal reception. MPE-FEC also improves impulse noise tolerance.

DVB-H broadcasting is attractive, because it makes use of high bandwidth channels with high transmission speeds. This means that a diverse range of high-quality TV services can be made available to mobile users. Furthermore, once some content is broadcast, there is no limit to how many people can receive the content within the coverage area. One-to-many broadcasting is a very cost-effective means to deliver media content to large audiences, when compared to one-to-one delivery.

DVB-H also enables the use of advanced video and audio codecs, such as H.264. Using these, up to 50 television or data channels can be broadcast over one DVB-H multiplex.

For cellular operators, DVB-H reception together with cellular connectivity opens up possibilities for TV-related interactive services such as voting, polls, gaming and e-commerce. Applications sourced from commercial pay-TV models such as pay-per-view can also be supported.

Apart from implementation costs, decision-makers tend to look at the time-to-market schedule of a technology. For DVB-H, the lead time is very short as products are being rolled out. The technology is based on an open standard. It has been tested, and it has a large manufacturer consensus to back it up. More than 270 broadcasters, manufacturers, network operators, software developers, regulatory bodies and others in more than 35 countries are committed to the DVB Project, an industry-led consortium that supports DVB-H technology for broadcast mobile TV.

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