Mobile phone TV : who wants it? by Marius Scheepers, Sentech Chances are that if you randomly ask ten people at a shopping mall whether they would like to be able to watch TV on their cellphone, they would all say ‘yes’. It is already possible to make a video call, reception showed that the system was even many as with 8 k) and the symbol period is view multimedia content and surf the net on a more rugged than fi rst expected, there were double that of the 2 k mode (half of the 8 k mode cellphone, so what’s the deal? Why is TV not concerns over DVB-T system performance with symbol period). This allows network designers there yet? regard to receiver battery life and reception the freedom to optimise transmission according reliability under severe receiving conditions. For to the most likely reception mode in the network. These questions are at the heart of various this reason DVB developed the 4 k transmission An advantage hereof is that a network designed international trials of technology known as mode in addition to the existing 2 k and 8 k to be most rugged for purposes of mobile DVB-H (digital video broadcasting – handheld). modes, added a further layer of forward error reception at high speed, would allow for easy So far the technical results look very promising correction (FEC) coding and designed a ‘time- reception at a given fi xed location. Naturally, it but, as these things go, ‘will the paying customers slicing’ scheme to cut down on battery power would be a trade-off between bitrate capacity come if we build it?’. Digital multimedia consumption. and signal ruggedness. broadcasting (DMB) - a competing technology which seems to have taken off successfully in Since it was well-known that Korea - may also yet fi nd the favour of large the 2 k DVB-T mode was more numbers of consumers. resilient to Doppler effects than the 8 k mode, the 2 k mode was Digital multimedia broadcasting favoured for mobile reception (ETSI TS 102 428) at high speeds. However, the DMB is based essentially on the ETSI TS 8 k mode proved to be more 300 401 DAB (digital audio broadcasting) robust than 2 k in the presence standard. Instead of only making use of of impulsive interference such MPEG2 (musicam) audio coding, as the DAB as unsuppressed vehicle ignition standard specifi es, it uses some of the available systems. This led to the 4 k capacity to encapsulate IP data, which could mode in which there are twice be video, audio, text, html – anything really, as many carriers per multiplex into an MPEG4 inner wrapper. This is then than in the 2 k mode (half as Fig. 1: An example of a DVB-H-enabled smartphone. wrapped in an MPEG2 outer wrapper, which is forwarded to the orthogonal frequency division multiplexing (OFDM) modulator, upconverted and transmitted. In Korea, the television application is particularly popular and handset sales have skyrocketed since the commercial launching of DMB services there about a year ago. The preferred spectrum for DMB is the VHF television band, which is almost fully occupied in South Africa and will therefore probably blow in the face of DMB deployment here. Digital video broadcasting – handheld (ETSI EN 302 304) DVB-H is based on DVB-T (ETS 300 744), the terrestrial standard for digital television broadcasting. The DVB family of standards has become dominant in most parts of the world and the latest addition of DVB-H will strengthen that dominance. Although testing of DVB-T mobile Fig. 2: DVB-H topology. 38 Elektron November 2005 Perhaps the most impressive aspect of DVB-H is also expected that handset manufacturers will almost certainly have to include broadcast signal is that of ‘time-slicing’. This technique sees the be investing heavily in the development of new distributors due to the sensitive nature of adding overall payload divided into ten time slots of battery/power technologies that would extend the services into the traditional broadcast frequency equal duration. Data belonging to a particular potential viewing time considerably. spectrum. application would always be transmitted in the All and all a very exciting prospect indeed and we So, where do matters stand? same time slot. This means that a receiver which look forward to the next decisive step in bringing has been tuned to receive a particular application DVB-H trials are being conducted in several television to the so-called fourth screen. e.g. “Cricket highlights”, would only need to have countries, notably Finland (Helsinki), USA Resources its reception circuitry active during the relevant (Pittsburg), UK (Oxford), France (Paris), etc. and time slot and ‘go to sleep’ during the other nine also right here in South Africa (Johannesburg • ETSI website : www.etsi.org time slots. Synchronising information in the – MultiChoice/Orbicom). Preliminary results are • DigiTAG : “Television on a handheld receiver signal would allow the receiver to “wake up” highly encouraging and show clearly that there – broadcasting with DVB-H”; Version 1; again just prior to receiving its designated time is a signifi cant market for mobile TV services. An www.digitag.org slot again, and so on. Data received in this way is important mobile TV conference took place in • Vodafone : Presentation by Christian Rauch titled buffered so as to allow for smooth play-out, albeit London during October, where the commercial “Mobile and Broadcast Convergence – perspectives subject to a small amount of latency. Through potential of this technology was expected to come for new services”; www.vodafone-rnd.com this technique the draining effect on the handset under the spotlight. Mobile operators have shown Contact Marius Scheepers, Sentech, battery can be signifi cantly reduced, theoretically a clear interest and for them it is now a matter Tel (011) 471-4400, by a factor of 10, thus increasing viewing time. It of fi nding a suitable business model, which will [email protected] ☐ 40 Elektron November 2005.