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DVB-H is the latest development from the DVB Project targeting handheld, battery powered devices such as mobile telephones, PDAs, etc.. The Digital Video Broadcasting Project (DVB) is an industry-led consortium of over 300 broadcasters, manufacturers, network operators, software developers, regulatory bodies and others in over 35 countries committed to designing global standards for the global delivery of digital television and data services.
The DVB-H specification was developed in June 2004 for accessing DVB services on handheld devices. Broadcasters initially supported the Quarter VGA (QVGA, 320 x 240 pixels) standard, while cellular phone carriers supported Quarter Common Intermediate Format (QCIF, 176 x 144 pixels) in 2002. DVB-H solves the rift between them. When the user watches a program on a mobile phone, there will be two types of content on the mobile phone screen -- a broadcast program (such as a drama) by a broadcast service provider, and custom data relevant to the program (such as online shopping information as to the shoes an actor in the drama is wearing) prepared by a telecom carrier. DVB-H Handheld: When DVB-T was first published in 1997, it wasn’t designed to target mobile receivers. However, following very positive experimental results, DVB-T mobile services have been launched in Singapore and Germany, with extensive commercial trials elsewhere. Indeed, with the advent of diversity antenna receivers, services which target fixed reception can now largely be received on the move as well. So why DVB-H? Battery life! Despite the success of mobile DVB-T reception, the major concern with any handheld device is that of battery life. The current and projected power consumption of DVB-T front ends is too high to support handheld receivers that expect to last from one to several days on a single charge. The other major requirements for DVB-H were an ability to receive 15Mbit/s in an 8MHz channel and in a wide area single frequency network at high speed. These requirements were drawn up after much debate and with an eye on emerging convergence devices providing video services and other broadcast data services to 2.5G and 3G handheld devices. Furthermore, all this should be possible while maintaining maximum compatibility with existing DVB-T networks and systems. Technical Characteristics
In order to meet the above requirements, the DVB-H specification includes: Time-Slicing Rather than continuous data transmission as in DVB-T, DVB-H employs a mechanism where bursts of data are received at a time – a so-called IP datacast carousel. This means that the receiver is inactive for much of the time, and can thus, by means of clever control signalling, be "switched off". The result is a power saving of some 90% and more in some cases. 4K-mode With the addition of a 4K mode with some 3409 active carriers, DVB-H benefits from the compromise between the high speed small areas SFN capability of 2K DVB-T and the lower speed but larger area SFNs of 8K DVB-T. In addition, with the aid of enhanced in-depth interleavers in the 2K and 4K modes, DVB-H has even better immunity to ignition interference. MPE-FEC The addition of an optional, multiplexer level, forward error correction scheme means that DVB-H transmissions can be even more robust. This is advantageous when considering the hostile environments and poor (but fashionable!) antenna designs typical of handheld receivers. Compatibility with DVB-T Like DVB-T, DVB-H can be used in 6, 7 and 8 MHz channel environments. However, a 5MHz option is also specified for use in non-broadcast environments. A key initial requirement, and an amazing feature of DVB-H, is that it can co-exist with DVB-T in the same multiplex. Thus, an operator can choose to have 2 DVB-T services and one DVB-H service in the same overall DVB-T multiplex. What of ATSC and ISDB-T? 2004 is all about mobile and portable multimedia. This sidelines the single carrier (8-VSB) ATSC system from the US. ISDB-T, developed and now deploying in Japan has a mode which could offer mobile datacasting services, but concerns about battery power, receiver cost and system complexity remain. DVB-T is deployed in some 50 countries and, with DVB-H, now provides a powerful tool to address new markets for DVB services. IP broadcasting based on DVB-T In 2002, broadcasters supported an idea of displaying a restricted type of content so as to avoid the user's attention being diverted from the program. They are now likely to seek a screen to be able to display both contents as long as they can be distinguished from each other. On the issue of whether to employ RMP, there are differing opinions in the broadcasting industry. According to some, there is no use of scrambling for copy control because this type of broadcasting provides low resolution-images at 15 frames per second on QVGA. Development of tuner modules and H.264 encoders that are to be embedded in cellular phones is accelerating. For example, makers are developing tuner modules at a power-consumption level of around 100mW, measuring 1.4mm in thickness, while a current standard model has 150mW-200mW power consumption and measures around 2mm in thickness. DVB-H and 3G Broadcasting is an excellent way of reaching many users with a single (configurable) service. DVB-H combines broadcasting with a set of measures to ensure that the target receivers can operate from a battery and on the move, and is thus an ideal companion to 3G telecommunications, offering symmetrical and asymmetrical bi-directional multimedia services. DVB-H trials DVB-H trials are an important element in system verification. Trials are now underway in Germany (Berlin), Finland (Helsinki) and US (Pittsburgh). Such trials will help frequency planning, and improve understanding of the complex issue of interoperability with telecommunications networks and services. In the meantime, the DVB-H documentation is being standardised through ETSI. (www.etsi.org) From trials to services DVB-H is generating significant interest in the broadcast and telecommunications worlds, and DVB-H services are expected to start as early as 2005. Indeed, one senior mobile telecommunications industry analyst is quoted as saying that he expects to see 100 million DVB-H capable handsets in 2007, growing to 300 million by 2009.
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