A new hybrid mobile broadcast technology platform developed by Professor Ulrich Reimers at Braunschweig Technical University in association with French transmission company TDF and GatesAir â€“ the so-called Tower Overlay over LTE-A+ (TOol+) system â€“ is set to be field-trialled from the Eiffel Tower from January 2015.
The technology – which embeds an LTE-A+ video steam within a standard DVB-T2 broadcast signal and combines elements of both cellular and broadcast networks â€“ could provide a solution to the current standoff between the mobile and TV sectors over a common approach to mobile broadcast standards.
The TOol+ field-trial will be accommodated within French transmission company TDFâ€™s on-going experiment with the Broadcast Multimedia Mobile (B2M) system, a DVB-T based initiative which launched in April last year in the hope that it might provide a possible replacement for Franceâ€™s now abandoned mobile broadcast TV programme. B2Mâ€™s aim is develop a new technology platform to distribute content to mobile terminals such as smartphones and tablets. In September, the TDF B2M pilot was granted an extension by the French regulator, the CSA, until March 2015.
LTE-A+ is an extended version of the current LTE-Advanced standard â€“ itself a souped-up version of LTE or 4G. The â€˜+â€™ stands for the fact that, among other elements, it adds the capability to access spectrum from â€˜high-tower, high-powerâ€™ terrestrial broadcast networks which use much bigger cells than those deployed in a typical mobile network.
The TOol+ approach accordingly delivers an LTE-A+ standard broadcast TV signal within a DVB-T2 carrier over a hybrid platform which combines a standard cellular 4G network with a standard DTT one as an â€˜overlayâ€™. This uses the same carrier model as DVBâ€™s T2-Lite mobile broadcast standard, in that it incorporates the LTE-A+ element using a special feature of DVB-T2 known as Future Extension Frames (FEFs). These in effect allow signals with completely different characteristics to be interpolated within a base DVB-T2 signal without interfering with it.
In a demonstration of TOol+ at IBC 2014 an 8Mbit/s DVB-T2 carrier was able to accommodate a 2Mbit/s LTE-A+ stream, with each broadcast being separated out and independently delivered to a DVB-T2 set-top box and a tablet PC containing an LTE-A+ chipset (see diagram above). The attraction of the set-up is that an LTE-A+ enabled mobile device does not need to have a DVB-T2 tuner in it â€“ all it needs is to be registered to the mobile operatorâ€™s system to receive its LTE-A+ broadcasts.
Reimers told Videonet that while there had been â€œlots of interestâ€ in the system, the â€œcrucial stepâ€ now was to get the mobile standards body 3GPP to accept LTE-A+ as a valid extension to LTE Advanced. The three partners were lobbying hard to have it accepted within a future LTE release, he said.
Reimers also noted that, â€œthe key element we are exploiting for providing this LTE-A+ service over a tower overlay network â€“ which is the FEFs in DVB-T2 â€“ will be included in ATSC 3.0 also.â€
This is the USAâ€™s next-generation DTT standard and Reimers said that if they could win over 3GPP as well, this would mean the TOol+ approach could be used within â€œsomething like 80% of the worldâ€™s standards.â€
Reimers added that â€œthe beautiful thing from the point of view of the broadcast network operatorsâ€ was that it meant that â€œtheir infrastructure, their towers overhead, are no longer confined to terrestrial broadcasts.â€ For mobile operators, it provided a solution to the fact that cellular networks would not be able to cope with the growing demand for live video.