How 5G will change your TV for good
Whether you were at CES 2019 in Las Vegas or not, you should already know that this year the keyword of the show has been 5G. Announcements by major mobile operators and phone manufacturers seem to suggest that commercialization of 5G will start sooner than expected, with an increasing number of deployments planned from 2019–2020 onward, initially based on the “5G early drop” 3GPP specifications.
5G is designed to improve every single aspect of the LTE mobile network, including a new radio access technology (5G-NR). Requirements cover three main classes of services:
- Enhanced Mobile Broadband (eMBB): access to multimedia content, services and data by humans
- Massive Machine Type Communications (mMTC): data exchange among low-power devices with minimal throughput and relaxed constraints in terms of delay.
- Ultra-Reliable Low Latency Communications (URLLC): connectivity with strict levels of availability and latency (autonomous vehicles, public safety, industrial control, robotics and drones, remote medical surgery)
As defined by 3GPP, these three, very different, classes shall all be offered by a single mobile network. The 5G platform is designed to be tuned and dynamically configured in multiple logically partitioned networks with different characteristics and customized QoS levels using a mechanism called network slicing.
Delivery of video streaming will exploit eMBB capabilities, that will be also the first target for early market deployments. 5G will be the platform for distributing high quality content to mobile devices and, with the so-called fixed wireless access, to connected TV or set top boxes in homes.
But this new platform, with its high spectrum efficiency, can represent an interesting way forward also for traditional TV broadcast terrestrial delivery (currently using DVB-T/T2, ATSC or ISDB-T technologies). In Europe, with the progressive transition of the 700 MHz spectrum to mobile broadband (to be completed by 2020–2022 according to EU rules) and the increasing demand in terms of bandwidth to provide high quality content, broadcasters are evaluating alternatives.
Will 5G networks be able to support broadcast linear TV services and their requirements? Is a progressive convergence to IP-based TV services in synergy with mobile operators, a sustainable model for the future of TV? And if yes, will it happen now?
A bit of history
In early 2000s, a collective effort to provide a means to enable TV on mobile phones produced the first DVB Handheld specification (DVB-H). The specification, published as ETSI standard in 2004, defined an additional module to be included in compliant mobile devices. The DVB-H demodulator, conceptually implementing a superset of the digital terrestrial receiver functionalities, was based on the same principles, trying to protect broadcasters’ investment and transmission equipment by ensuring compatibility with DVB-T transmissions.
This initiative didn’t take off. Commercial services were launched in a number of countries in Europe but scarcity of devices with DVB-H stacks and, above all, lack of a sounding and profitable business model, forced operators to shut down them.
A different approach was pursued by 3GPP with the Multimedia Broadcast Multicast Service (MBMS). In this case, the specification extended 3G UMTS network capabilities to support point-to-multipoint (PMP) distribution though severe constraints were imposed by limited bandwidth supported and static allocation of the spectrum.
The Evolved MBMS (eMBMS), is an extension of the 4G LTE system (starting from 3GPP Release 9 specifications). With eMBMS, an operator can decide to allocate a part of the bandwidth available in downlink in a cell (up to 60%) to broadcast traffic that will serve multiple devices with the same content: video, audio, files, etc… Data is delivered in a one-way fashion, each operator is responsible for the allocation of the multicast portion within his network, and content cannot be shared among different networks (needs to be replicated).
Content delivery is based on MPEG-DASH adaptive streaming but with a single representation or quality level per content. eMBMS doesn’t use HTTP, but instead adopts the FLUTE mechanism, designed to efficiently distribute files to devices (chunks in case of adaptive streaming).
Subsequent additions defined the MBMS operation on demand (MOOD), a mechanism to dynamically switch from unicast delivery to multicast when the number of devices accessing a particular content goes over a defined threshold. For example, when at least 3 users are watching the same content via unicast in an area, it may be more convenient to provide that content once via multicast, avoiding wasting resources, and transparently migrate those devices and users to this new stream.
A typical service scenario for eMBMS adoption, in addition to mobile TV, is “Venue casting”, where in a relatively limited geographical area like a stadium, a campus, or an exposition hall, a portion of the spectrum is reserved to multicast just for specific events. The audience can access additional content in real-time, provided as one or more linear channels available on their devices and showing, for example, instant replays or different views of the event. Each channel is delivered as a multicast stream potentially serving thousands of users without incurring in network congestion issues and service degradation.
The first eMBMS commercial service was launched in 2014, after several trials carried out by operators around the world. eMBMS requires the deployment of additional elements in the LTE core network architecture. Although these operations can be performed via software updates, a compliant user device is still required in order to access services. Verizon, in USA, attempted to commercialize a large scale eMBMS service (Go90) but eventually discontinued it. eMBMS adoption today, where existing infrastructures are already installed, is mostly confined to selected areas and enabled on event basis only.
Why isn’ t this model working? The first consideration is that launching widely available mobile linear TV services with eMBMS today doesn’t scale in terms of revenues to justify investments in the infrastructure either with Ad-funded or subscription-based models. Comparable live services delivered with the unicast OTT approach are still more profitable considering costs and potential user base. Another critical aspect is the lack of support in devices. eMBMS API has been recently included in Android, starting from version 8.1, but the number of devices supporting those capabilities is by far too limited, with some products disabling the features even if the underlying chipset would be eMBMS capable.
Towards a mobile network for Broadcast TV
In 2017, with Release 14, 3GPP introduced the Enhanced TV (enTV) feature: a new set of eMBMS extensions implementing a full broadcast TV stack in the LTE mobile network. Major additions are:
- A model supporting High Power High Tower (HPHT) transmitters, in addition to cellular cells, to create overlay networks able to cooperate and provide the required coverage in both rural and urban areas
- Larger Inter-Site Distance (ISD) at high spectral efficiency
- Support for up to 100% eMBMS carrier allocation to create dedicated broadcast networks
- A receive-only mode, in which devices can view broadcast content even without a SIM
- A transport mode that allows reuse of broadcast services without transcoding thus ensuring backward compatibility and minimal effort to migrate from legacy transmission systems
- A shared broadcast network, where different operators can aggregate their MBMS networks to create a common distribution platform without the need to replicate content
These additions made LTE, in its latest version, able to support both mixed multicast/unicast and standalone terrestrial broadcast services, defining a truly converged platform for content distribution. The European Broadcasting Union (EBU) and several broadcasters played an important role in those developments, ensuring that EU digital TV broadcast requirements, including public service regulatory constraints such as Free-to-air channels availability, were met.
5G & TV
A number of research projects are studying, prototyping and evaluating enTV in the context of LTE and upcoming 5G deployments: examples are 5G-Xcast, a H2020/5G-PPP project partially-funded by the EU; 5G Today, a project currently ongoing in Bavaria, Germany, and the 5GTN+ project in Finland. One of the objectives is to find the best solutions to exploit 5G enhanced capabilities, in particular using the new radio interface (5G-NR) for broadcast TV services.
3GPP is working on the evolution of enTV with a study on LTE-based 5G terrestrial broadcast, which should highlight gaps to match requirements already defined for 5G, and allow required updates to be integrated in Release 16 (scheduled for end 2019), whereas the design of a 5G-native eMBMS broadcast mode has been postponed after 2019. This means that broadcast capabilities on 5G-NR (for TV, but also for other services such as IoT or V2X) will not be available as part of the first 5G deployments.
In parallel, an increasing interest has been shown for the adoption of 5G as communication infrastructure for production and transport of audiovisual content. 5G, and the adoption of new, more efficient video compression technologies, can provide a great opportunity to simplify and enhance content production and contribution, reducing costs. Today live events with remote production require complicated and expensive setups that include wireless cameras with video relays to OB vans at the venue and satellite or fixed links to studios. This scenario can be greatly simplified using 5G. 5G capabilities will allow the use of a single, reliable communication link with high capacity and very low latency, to connect cameras directly to remote production studios. The same approach can be used also for studio-based production, without the need of local wired infrastructures, and it’s aligned with current market trends that are aiming at shifting audiovisual production to all-IP workflows.
These requirements, that include also synchronization of feeds and management of QoS and security, are part of an ongoing 3GPP Feasibility Study on Audio-Visual Service Production, promoted by EBU and other members.