If the cellular industry has its way, we should soon have access to live TV transmissions on our 3G mobile phones. How the TV signals reach the mobile, however, depends on which standards are adopted. Brian Lancaster explains the technology behind this quiet revolution…
June 2006 will be an important date for football fans the world over — it’s the start of the World Cup, which takes place in Germany. That dateline will be an important one for the global cellular industry, as most leading-edge networks want to have their real-time TV-on-a-mobile services operational by then.
But relaying TV — and video-on-demand services — to a cellular handset involves a lot more than building an analogue or digital TV tuning system into the mobile. As users of handheld TVs will have discovered, TV signals do not propagate well to TVs on the move.
The cellular networks must instead turn to new technologies such as DVB-H (Digital Video Broadcasting — Handheld) and 3.5G transmissions (more of which later) to meet their needs.
Following its ratification by the European Technical Standards Institute (www.etsi.org), DVB-H has moved off the drawing board and into the real world, with a consortium of European firms — including Nokia, MTV and YLE (a Finnish broadcasting company) — already trialling the technology in Finland. The DVB-H datacasting trial, which started in early March, gives Finnish triallists real-time access to a cluster of TV channels, including BBC World, CNN, Eurosport and MTV, on Nokia 7710 handsets equipped with a plug-in transcoding device.
DVB-H, however, is more than just receiving digital TV transmissions. The technology, like digital terrestrial and satellite, allows users to receive ancillary files, including pictures, video clips and music, for viewing and listening on the move.
Unlike digital terrestrial and satellite transmission standards, however, DVB-H uses a ‘data burst’ or time-slicing approach to the carriage of signals across the available radio spectrum. Using this transmission technology reduces DVB-H power consumption on mobile phones to roughly the same level as a voice call, although the handset vendors are still working hard to develop lower-power display screens.
Unlike 3.5G technology, more of which in moment, DVB-H does not use the normal cellular transmission path to carry the real-time TV signals to the mobile. Signals are, instead, carried across a separate network, although it is expected that the base stations for commercial DVB-H deployments will be co-located, where appropriate, with existing GSM and/or 3G base stations.
DVB-H’s main claim to fame is that it supports frame rates of up to 25 frames per second (fps), compared to the 5 fps seen on existing video streaming services. Standard TV broadcasts operate at between 25 and 30 fps.
The difference between streamed video files seen on mainstream 2G and 3G mobiles (and networks) at the moment was clearly illustrated at the giant CeBIT show in Germany recently, when Siemens showed off its DVB-H prototype handset. At the show, held in Hannover, Siemens showed its prototype handset sending text messages at the same time as receiving a DVB-H transmission. The prototype also had an integral 128 megabytes of memory for program storage, as well as a memory card slot for expanded storage facilities.
At AlanDick, we think that the interactive element of DVB-H has significant potential. Users of a mobile could, for example, watch a series of film trailers on their handset and then reserve a seat at the movies using the return data channel.
Vodafone Germany is planning to stage a trial of DVB-H transmissions using around 100 of the Siemens prototypes in a major German city later this year, whilst O2 is planning to work with NTL and Nokia for a six-month trial of DVB-H amongst 250 customers in Oxford. Although details of the O2 trials were still at the planning stages at press time, the game plan is to use a single-frequency network with nine base stations covering a 120 square kilometres area around Oxford.
O2 has yet to confirm which handset vendor it will be using for its trials, although it should be noted that Siemens is not alone in developing DVB-H-compliant mobiles. Samsung, for example, also showed off its first DVB-H handset at CeBIT. The handset — which supports both CDMA and GSM networks, making it suitable for global usage — does not feature any recording facilities.
Critics of DVB-H point out that movie trailer interaction by customers is nothing new, but the key feature of DVB-H is that it enables easy viewing of TV transmissions — and interaction, if appropriate — in real time, just like on a regular TV.
The 3.5G alternative
But DVB-H isn’t the only TV-on-a-mobile technology on the block, as users of 3G handsets on Hutchison 3G, Vodafone and Mobilkom Austria networks will be aware. The alternative technology to DVB-H is known generically as video streaming, which has the advantage that it can operate across multiple mobile standards, ranging from 2.5G (GPRS) right through to 3.5G.
3G video streaming is already quite popular in several countries, but is not really suitable for real-time TV transmissions because of the relatively low (150 to 220 kilobits per second — Kbps) speeds currently available on 3G networks. Plans currently call for most 3G networks in Europe and Asia to support mobile data speeds of 384 Kbps within the next few years, but even this speed is only just enough to support a VHS tape quality TV transmission with minimal bandwidth headroom. For faster transmissions we have to turn to 3.5G technology, better known in some circles as HSDPA (High Speed Downlink Packet Access), which is now entering trials on both sides of the Atlantic.
The development of HSDPA is thanks to a number of software modifications for 3G networks that Lucent, Motorola and Nortel have developed in co-operation with carriers such as Cingular in the US and O2 in Europe. By tweaking the way in which data is transmitted from the base station to the mobile, Lucent and Nortel claim that data transmissions can be speeded up from the current 384 Kbps maximum with 3G to around 3.6 megabits per second (Mbps) on 3.5G. Eventually, the two vendors claim, it should be possible to push data download speeds up to a theoretical maximum of 14.4 Mbps on the downlink and 5.8 Mbps on the uplink.
In trials, Cingular and O2 say they have observed download speeds of, respectively, 2.0 and 2.9 Mbps, on their test 3.5G services.
Even under a full 3G cell site loading, data speeds in excess of 1 Mbps are expected — more than enough room for point-to-point mobile narrowcasts of various channels.
Although HSDPA is a technical compromise compared to DVB-H’s shiny new technology, HSDPA has the key advantage that it uses existing 3G network infrastructure with software, rather than hardware, modifications. Put simply, this means that HSDPA does not need an overlay network of new base stations. Thanks to this fact, it looks likely that 3.5G technology could reach the market more quickly than DVB-H.
In the US, Lucent and Cingular remain coy on 3.5G timescales. Europe’s O2 is more ebullient. It expects to introduce commercial HSDPA on its 3G networks some time during 2007.
Next year’s World Cup could force their hands on timescales, so our best guess here at AlanDick is that 3.5G-based TV-on-a-mobile transmissions could be soft launched as early as the spring of next year — but don’t expect too many handsets to be available.
