Two weeks ago the DVB Project published A081 - Draft DVB-H Standard. Last week, the technology was demonstrated at the Nokia Connection event in Singapore. DVB-H is a standard for broadcasting content and data to handheld devices. In Singapore, Nokia, MediaCorp Technologies, M1 and the Media Development Authority (MDA) of Singapore jointly demonstrated a live end-to-end mobile phone TV broadcast using the digital terrestrial TV transmission infrastructure managed by MediaCorp Technologies. The programming was received using a Nokia Streamer mobile DVB-H receiver attached to a Nokia 7700 media device. Details on the Singapore test can be found in the Nokia press release Live Demo of Mobile Phone TV over DVB-H.
While most broadcast engineers are familiar with DVB-T, the terrestrial DTV standard used in Europe and many other countries around the world, DVB-H is not as well known. The DVB-H standard was designed specifically for use with handheld devices, which require a standard that would work in the difficult reception environments in which they are often used and that would allow the use of tuners with greatly reduced power consumption. One of the ways DVB-H achieves the power savings is using a time-slicing system where data is received in bursts rather than continuously, as is the case with DVB-T. This allows the receiver to be switched off between the bursts, resulting in a power savings of 90 percent or more. It also allows one receiver to monitor adjacent cells using different time slices, which allow for smooth hand-offs as the receiver moves from cell to cell.
DVB-T specifies COFDM modes with approximately 2,000 (2K) or 8,000 (8K) carriers. DVB-H adds a 3,409 active carrier (4K) mode, providing a trade off between the high speed, small area single frequency networks (SFN) coverage of 2K DVB-T and the lower speed, larger area coverage of 8K DVB-T. A robust multiplexer level forward error correction scheme called MPE-FEC is part of the standard. MPE-FEC has additional Reed-Solomon coding for IP datagrams, providing "virtual interleaving." This allows greater resistance to Doppler and provides a several dB improvement in tolerance to impulse noise interference.
DVB-H can be used in a dedicated network or as the high priority stream in a DVB-T hierarchical transmission multiplex.
Although recent publicity on cellphone TV might give the impression that DVB-H is here now, it is still a draft standard. The validation process of DVB-H has started and is expected to be completed in the fourth quarter of 2004. Commercial DVB-H networks and services are scheduled for the year 2005.
Additional information on DVB-H, the standard and implementation, can be found on the DVB-H /IPDC web page.
