Although Europe-centric with Huawei the only participant from outside the continent, the move is significant because it signals the broadcasting industry’s switch of focus from digital terrestrial transmission (DTT) to broadcasting over cellular as the principle over the air delivery medium over time. From over a decade ago, spectrum has been reallocated from DTT to cellular networks triggered by release of the so-called digital dividend, where frequencies are liberated by the switch off of less efficient analogue channels. Since then there has been pressure to continue transferring spectrum from DTT to cellular in the face of rampant demand for mobile data fed largely by increasing consumption of video on mobile phones.

Such video is predominantly unicast, which is highly inefficient for transmission of popular live content received almost simultaneously by large numbers of users distributed across a region. In such cases a lot of core and backhaul network is saved by transmitting the content in single streams out to radio towers in cells where there are users wanting to receive it, and only then breaking out into unicast streams for each device.

Round in Circles

That comes full circle back to broadcasters, because now cellular operators are interested in multicast technology to reduce the load on their network infrastructure. There have been many false dawns in the past with a succession of attempts to get mobile broadcast, or strictly multicast, on the road. There was for example the DVB-H Handheld standard, Qualcomm’s proprietary MediaFLO and then more recently LTE Broadcast/Multicast originally promulgated by US telco Verizon among others. All of these failed for a variety of reasons, some technical, but primarily because all the required ingredients did not come together.

The main deficits were lack of conviction by mobile operators, lack of support in handsets, not incorporating the capability at scale in the network infrastructure, lack of services or content, along with inability to transmit and play back on mobile devices at sufficient quality. All of those deficits are now at last being overcome or certainly will be in the 5G era, with for example higher bandwidths combined with improved smart phone displays enabling playback at HD or even Ultra HD quality and growing support from within the cellular industry. There are also emerging potentially profitable use cases apart from video that will require point-to-multipoint transmission, for example sending real time traffic updates in the automotive sector and PPDR (public protection and disaster relief).

DTT Battle Lost

For broadcasters though, having essentially lost the battle to defend DTT capacity, the challenge now is to ensure that their voices are heard in the debate over allocation of spectrum and deployment of point-to-multipoint multicast technologies within 5G infrastructures. There is a danger of the infrastructure development being dominated by the mobile industry, which is one reason why the EBU decided to set up 5G-MAG.

“Much has been said about the potential for 5G networks to play a central role in media delivery in future,” said Antonio Arcidiacono, EBU Director of Technology & Innovation. “One of the big challenges, however, is to ensure that new 5G features such as broadcast capabilities are supported by network infrastructure and user devices.”

5G-MAG is also aware of past failures and the need to ensure that momentum does not fizzle out again this time round. Arcidiacono identified this as a “chicken and egg” challenge where different interdependent components need to be erected at the same time. “The vendors require certainty regarding market adoption, which will be driven by the existence of new services that rely on these new 5G features,” said Arcidiacono. “If that’s the chicken, then the egg is that the service providers will only invest in such new services if they are sure they can reach the end users. 5G-MAG hopes to foster the simultaneous emergence of both the chicken and the egg.”

Joining Together

5G-MAG itself is focusing mostly on the commercial aspects of bringing these pieces together, given that the underlying technologies are either in place or being developed elsewhere. Objectives include encouraging development and commercialization of 5G chipsets and user terminals that support media use cases. It will also aim to broker agreements between content providers, device makers and service distributors. Over content production, 5G-MAG will have a slightly more technical slant by stimulating development of more efficient production workflows.

Some of the relevant technical work has in fact been done in another European project called 5G-Xcast set up to develop and demonstrate a novel 5G network architecture optimized for large scale immersive media delivery. This is being subsumed into 5G-MAG since it is working on relevant technical themes, with three primary objectives. First is to develop multicast point-to-multipoint (PTM) capabilities for 5G that take full account of all use cases including automotive and the Internet of Things (IoT) generally, while specifically evaluating spectrum allocation options for 5G broadcast deployments.

5G Multicast

Second is to design an adaptable 5G network architecture with standardized network interfaces for dynamic and transparent switching between unicast, multicast and broadcast modes, with ability to have them running in parallel as well. This should include built-in caching capabilities to ensure QoS and allow for slight variations in delay across the infrastructure. The third objective is more evangelical, to demonstrate the key 5G innovations for the vertical use cases including media and entertainment.

Under the first category, the main objective is to overcome technical limitations in earlier incarnations of mobile multicast/broadcast that contributed to their failure, especially deficiencies in the later eMBMS used in LTE Advanced. These lead on to the second objective because the aim is to make mobile networks more flexible so that services can switch readily between multicast and unicast modes. One of the key steps here is to separate the radio access network (RAN) within cells from the core network, so that each can adapt independently to a wide variety of requirements with differing QoS requirements that themselves may vary according to user demand, traffic flows, network operator preferences and requirements of given content. The ability to adapt radio spectrum utilization in 5G network architecture dynamically is being studied and will be demonstrated as part of that third objective.

Multicast Convergence

One possible criticism is that 5G-MAG is too Euro-centric. After all, the 5G-Xcast project was set up with a mandate to prepare Europe for 5G broadcast and ensure that its companies are ready to compete on the world stage. On the other hand, the EBU has historically carried its remit beyond Europe’s borders and some of the vendors among the 50 plus 5G-MAG members are global companies, albeit headquartered in Europe. Samsung is the only non-European member of 5G-Xcast, although Huawei has joined 5G-MAG. Other members of 5G-MAG include French encoder maker ATEME, test and monitoring group Rohde & Schwarz, satellite platform operator Eutelsat and video infrastructure provider Enensys, along with broadcasters Bayerischer Rundfunk, Cyfrowy Polsat Group, France Télévisions, Italy’s RAI and the EBU itself.

There are various other initiatives focused on convergence between multicast and 5G. One involves South Korean mobile operator SK Telecom, Sinclair Broadcast Group of the US and Samsung subsidiary Harman International. These have teamed up to develop a broadcast network over SK Telecom’s 5G infrastructure using the ATSC 3.0 suite of TV transmission standards designed to combine broadcast and broadband.