DUBLIN, Ireland - Europe's Digital Video Broadcast group has launched an ambitious standards effort designed to marry the cell phone network infrastructure with terrestrial digital TV broadcasting.
"This has been secret up until now," said Ulrich Reimers, a professor at the Institut fuer Nachrichtentechnik (Braunschweig, Germany) and chairman of DVB's Technical Module, who described DVB-X to small groups of engineers at the DVB World 2003 conference here last week.
The specification would be used for distributing "audiovisual and multimedia services to all citizens, independent of their location," said Goeran Wahlberg, Nokia Corp.'s director for concepts and technology. "The world is going increasingly mobile," said Wahlberg, who predicted that this "mobility-improved transmission standard for terrestrial digital TV" will become "a mandatory spec for handheld devices in the future."
DVB-X is envisioned as a "one-to-many" broadcast project, enabling the distribution of music, film clips or other multimedia content to a large audience via mobile handsets. Most observers agree that broadcasting is a cheaper, more efficient transmission method than what 2.5- or third-generation cellular-network operators could provide.
The DVB group, which previously focused on the development of a broadcast platform, appears to be shifting gears in search of a new broadcast paradigm that exploits the growing momentum of mobile technology. Nokia's Wahlberg said the new mandate within DVB and the European Commission entails a "multiplatform" approach that effectively combines digital TV with Universal Mobile Telecommunications System and General Packet Radio Service cellular technologies.
The emerging DVB-X scheme is considering several extensions to the existing DVB terrestrial television standard, called DVB-T, Wahlberg said (see chart). They would address power consumption and data rates and would add specialized content delivery capabilities. Power is a particularly tricky issue.
This is not the first time industry has pondered using the DVB-T spec as a way to distribute video for mobile devices. But while the terrestrial standard is flexible enough to fulfill most commercial requirements for DVB-X applications, Reimers said it cannot deliver "digital TV broadcast for 24 hours [a day] on a mobile handset powered by a standard battery."
Ready by 2006
The ad hoc DVB-X technical group is therefore seeking technology for use in its specification. Responses are due by the end of March, with commercial implementation targeted for around 2006. Reimers said the list of DVB-X technical requirements includes power consumption of less then 100 milliwatts for the complete front end, "including the RF parts"; a data rate of 15 Mbits/second; operation in a large, single-frequency network; reception at high driving speeds; and only one antenna.
The ad hoc group hopes to achieve backward compatibility with DVB-T in the first phase of its work. "But if a full scope of its advantage cannot be achieved, we may move on to a new scheme that is not necessarily compatible with DVB-T," said Nokia's Wahlberg.
At the same time, another ad hoc group is drawing up a framework for convergence of the two transmission platforms-DVB-T/DVB-X and GPRS/UMTS. "Our job is to bring together broadcast and telecom worlds," said David Crawford, chairman of the DVB's UMTS ad hoc group, which consists of broadcasters, telecom operators, network equipment vendors and system companies.
Combining the two platforms in one handset might be easier said than done. The building blocks required for such a platform include everything from front-end and signal-processing technology to Internet Protocol (IP) infrastructure for DVB services and new coding schemes.
Handsets, for example, would require a convergence device able to receive signals from cellular networks as well as DVB-T/DVB-X broadcast transmissions. A handset would also have to process IP data packets and video signals distributed over MPEG transport streams.
To complicate matters, the software architecture built into such a handheld device would have to handle two software platforms: one currently in development by the Open Mobile Alliance for the mobile industry, along with the DVB's interactive Multimedia Home Platform.
By mapping the different blocks into a DVB/UMTS framework, "we are trying to figure out who needs to talk to whom," said Crawford.
Independently of the DVB-UMTS work, mobile industry groups such as the Third Generation Project Partnership are working on a Multimedia Broadcast Multicast Service (MBMS), with a 2010 goal for launch of a spec enabling audiovisual broadcasting over the cellular network, Crawford acknowledged. The "problem is that [MBMS is] also aiming to offer broadcast through a dedicated channel," he said. The use of dedicated channels means mobile operators that choose to broadcast content would use up a huge amount of capacity that would otherwise be devoted to basic communication services.
In theory, "2 Mbits per second can be made available over UMTS, if you are standing very close to a basestation," said Crawford. But in reality, the available bit rate over UMTS is more likely to be "about 144 kbits/second."
Rather than compete with the mobile industry's emerging MBMS spec, DVB-X hopes to solve the wireless operators' dilemma by complementing their services with broadcast offerings. The UMTS ad hoc group's effort is complicated, Crawford said, largely because GPRS and UMTS are "not yet constant and stable platforms, with different equipment manufacturers adding some proprietary implementations."
Nevertheless, he said his group is preparing technical reports for a DVB GPRS/UMTS handbook that will be issued later this year.
Meanwhile, another DVB technical group, responsible for evaluating new audiovisual-content formats, is eyeing the DVB-UMTS convergence platform as a possible home for audio/video applications using the emerging H.264 compression standard.
H.264-based applications can be targeted at "a 176 x 144[-pixel] QCIF-resolution display on a UMTS phone or PDA, by transmitting content at a typical bit rate between 50 and 100 kbits/s," said Ken McCann, director of ZetaCast and chairman of the DVB's AV coding group.