It is only a decade since the broadcasting industry was fighting an increasingly desperate but determined rearguard action to defend its precious digital terrestrial spectrum in sub-GHz bands against the inexorable advance of cellular services. Since then the contagion has reached DTH satellite transmission as well as that started eroding first to fixed line OTT video transmission and ultimately onto 5G as that encroaches via FWA (fixed wireless access).
Now the broadcasting world seems to have moved on to accept loss of its spectrum, or most of it, even embracing its impending convergence with mobile services. This is not just recognition of inevitable defeat in the spectrum wars but also that broadcasting was in any case migrating to streaming and converging with broadband, exploiting interactivity to enhance the experience for viewers.
Such sentiments have shown up in various recent surveys, including one on behalf of Nevion, a Norwegian vendor of virtualized IP media transport technology now 45% owned by Sony. The survey found that 82% of broadcasters now believe cellular networks driven by the 5G movement will eventually replace both traditional DTT and satellite broadcast distribution as the preferred way to access TV content, while over a third expect this to begin happening within the next two years.
The trend is broadly welcomed, with the overwhelming majority, 94%, believing that migration of services to 5G will most likely increase consumption of their content.
“5G technology can potentially deliver OTT broadcast services with the quality required not only for mobile devices, but also for TV screens at home,” said Andy Rayner, chief technologist at Nevion. “This could mean, as our research uncovered, that 5G is eventually likely to usurp DTT for consumers at home as well as on the move. In the long term, it is likely that 5G mobile technology could become the standard means to deliver terrestrial television.”
We should consider though that this talk of 5G replacing traditional broadcast is misleading. It is true that some legacy pay-TV operators may be threatened by this trend, and also that mobile services will replace fixed broadband in some cases. But it really represents a long-standing convergence between over-the-air broadcast and online unicast distribution with cellular at last competing with fixed-line broadband.
Increasingly often it is the same telcos delivering fixed line and mobile services in any case and it will be the same broadcasters or rights holders providing the content.
The story began well over 10 years ago in the case of DTT because of the ‘digital dividend’ yielded by switch ver from analog to digital terrestrial transmission. This reduced the spectrum needed to deliver a given bouquet of TV channels and regulators started reallocating the frequencies liberated to mobile services with their rapidly growing generation of data as the smartphone era got underway.
But broadcasters themselves faced growing demands through proliferation of content and increasing video resolution requiring higher bit-rates for a given channel. This led to a campaign from broadcasting lobbyists spearheaded by the EBU (European Broadcasting Union) and fought out at successive World Radio Conferences, especially those of 2008, 2012 and 2015.
The battle was essentially lost for broadcasters in progressive stages, causing some teething troubles even when resentment had subsided on the broadcasting side. The first cellular deployments exploting the digital dividend occurred in the 800 MHz band, causing problems through interference to DTT signals from the mobile networks that were resolved in various ways including filters and guard bands. Then came the second digital dividend in the 700 MHz band, where the LTE uplink was placed in the lower part of the band. This led to the coexistence problem widely discussed at WRC-15.
Although that is now history, the spirit of DTT will live on as broadcast or multicast overlays onto cellular. This is part of the convergence process where broadcasters will harness the interactive unicast capabilities of cellular but also impose an overlay layer that operates very much like DTT does from taller masts, using the High Power High Tower (HPHT) model.
This evolved from the 3GPP’s original and largely unsuccessful LTE-Broadcast to become eMBMS (enhanced MBMS), with addition of HPHT to enable more efficient distribution like DTT. It incorporated SFN (single frequency network) operation to allow the same bandwidth to be reused for a given channel in every cell. Crucially, eMBMS also brought support for a wider variety of mobile device types, with new options for broadcasting to LTE-enabled CPE devices such as smartphones and tablets.
3GPP Release 14 then kicked in by defining an extended guard interval known as a cyclic prefix to enable wider area coverage, while also introducing modes to support operation without SIM cards. This opened the door to mobile broadcast services not tied to a traditional cellular subscription, as long as devices supported the relevant radios.
This also opened the door to hybrid networks combining cellular with DTT infrastructure, trials of which started in 2019. However, it also became clear that the HPHT model is not always optimum for mobile broadcast, depending on terrain and population density among other factors. For that reason there is also interest in the alternative LPLT (Low Power Low Tower) approach, often to complement HPHT so that the two coexist across a whole cellular network.
HPHT is generally more cost effective for mobile broadcast. In urban areas though a HPHT approach may fail to enable sufficient coverage indoors, or even at street level in the vicinity of tall buildings. After all, DTT transmission, even though it occurs at frequencies below 1 GHz that have far greater range than, say, millimeter wave, still requires substantial aerials to ensure adequate reception for TVs in homes. For this reason, hybrid arrangements have been proposed and found optimal for networks combining rural and urban coverage.
Meanwhile, DTT standards have evolved to embrace IP transmission at a higher level of interaction, notably with the US ATSC 3.0. A quick point to note here for those unfamiliar with digital terrestrial is that DTT standards emerged on a regional basis with four main variants. These were the DVB-T followed by second generation T2 in Europe plus a few other countries, the ATSC in North America culminating in the third generation 3.0 version now being deployed, Digital Terrestrial Multimedia Broadcast (DTMB) in China, and Integrated Services Digital Broadcasting (ISDB) in Japan. The international ISDB-T version of the latter has been deployed in various Latin American countries, including Brazil and Argentina.
All of these have been converging with broadband under various guises, as HbbTV in the European Union, hybridcast in Japan and Ginga in Brazil. More recently the increasing importance of fixed and mobile broadband IP delivery for TV services has taken these standards further, notably under ATSC 3.0 in the US and the DVB-I (Internet) specification in Europe.
Convergence is also being driven from the 5G side by support for non-3GPP access technologies, which can then be used over the same infrastructure for multiple services. This takes convergence up to the application or service level, so that for example the interactive 5G network can deliver personalized or targeted content to users over a hybrid offering also delivering broadcast channels over the ATSC 3.0 network.
Such an offering has already been demonstrated in the US by SK Telecom, Sinclair Broadcast Group and automotive parts firm Harman International, to deliver TV to in-car infotainment systems. This operates over a Sinclair ATSC 3.0-based TV broadcast network combined with SK Telecom’s 5G network to deliver UHD (ultra-HD) video and audio, with advertising targeted to individuals identified over the 5G network, as well as broadcast of advanced emergency alerting.
Until recently, it has generally only been possible to deliver the same blanket spot ad to all TV viewers over digital terrestrial, but now ATSC 3.0 allows targeting via either fixed or mobile broadband networks. It is possible to go further by delivering localized content over-the-air on the basis of zones with vehicle positions identified by the 5G service. In this Sinclair case, as vehicles enter a given zone, they can receive real time traffic and information such as location and menu of nearby restaurants over the ATSC 3.0 network to avoid clogging the 5G network with multiple unicast updates.
SK Telecom has also demonstrated its multi-view service here combining 5G and ATSC 3.0 within a given video transmission to show multiple camera views, valuable for sports broadcasting. The ATSC 3.0 network transmits video taken from the principal main camera, while the 5G network streams live feeds from subsidiary cameras around a stadium or venue.
This gives a taste of things to come as 5G converges with terrestrial broadcast. In time it will all come under the orbit of 5G, but still exploiting that synergy between unicast and multicast/broadcast.