Time for some radical thinking at UHF?

The history of the UHF broadcast spectrum has been one of gradual transfers of blocks from TV broadcasting to cellular. This included the 800MHz block used for 4G and the 700MHz block for 5G. In some countries, such as the US, 600MHz has also been transferred to cellular. Simple extrapolation is leading to the question of whether more spectrum should be moved from TV to cellular.

Before going further, it is important to note that there are huge national differences. Some countries barely use terrestrial TV, others still have a large population that rely on it. Some have excellent broadband that can deliver streaming TV, others have less comprehensive connectivity. Hence, the issues will vary by country.

The key drivers of the past transfers of spectrum have been:

1.??? Ever-growing demand for more cellular data usage, leading to the need for more spectrum to meet demand.

2.??? Improved TV broadcast technology allowing for more channels to be broadcast with less spectrum.

But these drivers are changing. Firstly, as I showed in my book “The End of Telecoms History” growth in data usage is slowing, and usage is likely to plateau in the next few years. Without much growth there is little need for additional spectrum. Of course, operators will always value more spectrum as it may be useful and it may allow them to reduce costs, but their willingness to pay high prices will be much reduced. Secondly, improvements in broadcast technology are diminishing – the low hanging fruit has been picked. There is still some scope for reduction but it is less than in the past.

While these drivers have weakened, a new one has emerged. Terrestrial TV networks are becoming increasingly unaffordable. As more viewers move to other platforms – primarily streaming services – then the number of viewers of terrestrial TV decreases and hence the cost per viewer rises. Also, many terrestrial TV networks are aging, and there could come a point in the next decade where significant investment is needed in maintaining masts and renewing the active transmission equipment. In some countries, such as the UK, there are dates set for review and possible renewal of the transmission licenses which could act as catalysts for a debate on whether terrestrial transmission is becoming unaffordable. A time could come where the terrestrial TV networks may voluntarily turn off and hand back the UHF spectrum.

Against this backdrop of changing drivers, the concept of transferring another tranche of UHF spectrum to cellular while keeping terrestrial broadcasting alive makes little sense. It would involve significant cost to re-engineer terrestrial TV networks and may require viewers to update receiving equipment and yet the benefits of the released spectrum will be small, and the remaining viewing base on the upgraded TV network likely to dwindle. Likewise, there is little scope for a cost-reduced platform. Reducing the content transmitted does not materially change the cost of operations, only reducing coverage would do that. But a network with partial national coverage makes little sense.

Instead, the key decisions become:

1.??? When will we turn off the terrestrial TV network (which may not be for 10 years or more)?

2.??? After this, what should we use the UHF spectrum for?

The switch-off date will vary by country and will depend on the cost of maintaining the terrestrial TV platform, the penetration of streaming TV and the willingness of politicians to address an issue that could generate bad publicity for them. Around the mid-2030s might be a reasonable estimate for most countries.

What should we do with the spectrum at that point? There could be around 200MHz of UHF spectrum roughly in the band 470-690MHz in most countries (less in those like the US that has already repurposed the 600MHz band).

A first point of note is that PMSE (wireless microphones and similar) is currently a user of the UHF band. Mostly this is on a shared basis, but in any future bandplan some dedicated spectrum could be found for on-going PMSE usage, perhaps 10-20MHz.

Despite the slowing growth, cellular remains a possible user. But these lower frequencies are less attractive to cellular networks. Optimal antennas at 500MHz are around 30cm long – too big for most handsets. Hence, the benefits of improved propagation at lower frequencies may not be realised. These factors suggest that the spectrum will be of relatively low value to the operators, implying other applications might be considered.

Alternative applications might include wide-area IoT networks, satellite direct-to-handset systems, spectrum for utilities such as power networks, railway spectrum, and unlicensed or lightly licensed spectrum for innovative new applications. There is more than enough spectrum for each of these applications to gain 10-20MHz alongside PMSE and cellular.

While switch-off may still be a decade away, it is time to start re-casting the debate away from taking the next slice of spectrum from broadcasting, to what to do with the entire band when broadcasting chooses to vacate. Putting in place the studies that can show the benefits of various uses, and then the international spectrum allocations that allow them will mean we can make clear, rational decisions when the time comes.