DVB-H: a win-win technology?

If you've been tracking what's likely to be coming soon on advanced mobiles in the future, you'll probably have read about receiving digital TV transmissions on your cellular phone.

The media bandwagon started in the spring of this year when several cellular operators around the world announced they were staging pilot tests of one of the technologies behind mobile TV, DVB-H.

DVB-H is an interesting hybrid communications medium. Whilst a DVB-H-compliant handset will rely on the CDMA, GSM, 3G or similar cellular network for voice, SMS and mobile Internet surfing, DVB-H allows the phone to receive its streamed TV "signals" from an entirely separate broadcast network.

This overlay approach to DVB-H is the key to its success to date, as it means the cellular networks do not have to invest in upgrading their own network - they can rely on one or more third parties to roll out their own series of DVB-H transmitters. The technology behind DVB-H is enormously flexible, allowing, for example, the use of higher power DVB-H transmissions from fewer transmitters than are used for standard cellular signals. In addition, the technology is sufficiently flexible to allow for regional and even single city coverage, rather than requiring an investment in a national network.

The real beauty of DVB-H, however, is that consumers are already used to carrying around a portable TV receiver in their pockets or purses - most of today's mobile phones already have a colour screen, so all that is needed is the inclusion of DVB-H receiver circuitry. For most people in Europe, the concept of viewed streamed TV on their mobile is a useful addition to the growing list of features for their pocket smartphone.

In many parts of the world, such as Africa and Asia, though, conventional TV transmissions are limited to just one or a few channels. For such consumers, offering them a wide choice from a carnet of channels - or even near video-on-demand from a streaming program source - represents a completely new entertainment medium.

The BBC's director general, undoubtedly had one eye on DVB-H technology when he announced plans for a MyBBCPlayer online service in 2006. Now known as iPlayer, the service offers rolling seven-day historical access to all of the BBC televisual and audio channels via the Internet.

But what about the technology behind DVB-H? Where is the industry so far in terms of standards?

Quite some way forward it seems, as the DVB-S2 standard - which was ratified by the European Telecommunications Standards Institute (ETSI) in April of 2006.

This is designed as a replacement for the DVB-S standard, now a decade old, that is used in most digital satellite TV systems. Unlike DVB-S, DVB-S2 was designed from the ground up to eliminate signal synchronisation problems in marginal reception conditions. The new standard also allows for better usage of the available bandwidth.

In addition to its improved performance and spectrum efficiency, the new standard supports an adaptive coding and modulation (ACM) transmission scheme that allows capacity to be optimised for individual - or groups of - receivers. Under this feature, receivers report their forward link signal-to-noise ratio back to the transmitter, which can then adjust the modulation and forward error correction parameters to suit. According to some sources, this ACM scheme can effectively double the available bandwidth on a typical signal, when compared to DVB-S.