If you live in the heart of a major city, it’s easy to take mobile network coverage for granted.
If you live in a rural county like Cornwall or Pembrokeshire, you’re unlikely to be so blasé.
Mobile network coverage varies hugely across the UK – itself a hugely varied nation combining dense and sparse populations, mountains and metropolitan areas.
The Scottish Highlands are home to fewer people than Wolverhampton, yet this single council region occupies a larger geographic area than Belgium.
As such, consumers tend to rely on maps to understand mobile network coverage in their home region.
But how do the network operators themselves calculate it?
Fields of expertise
There’s a big difference between calculating the range a mobile base station could theoretically achieve, and fully realising that potential in a field at the base of a hill.
This has historically led to a disconnect between engineering tests and consumer experience, with the former generally more optimistic than the latter.
That’s why you might find yourself in an area supposedly bequeathed with good outdoor network coverage, holding your smartphone in the air as you vainly try to gain a signal.
Mobile operators know how far their technology can transmit GHz data, and how many devices each base station can support on the frequency it broadcasts across.
What they can’t legislate for is the combined effect of varying consumer demand, ambient weather, temporary obstructions and other real-world factors.
As a result, the network coverage maps published on network operator websites tend to be relative rather than absolute guides.
The O2, EE and Vodafone coverage maps recognise exact postcodes, with breakdowns for 2G, 3G, 4G and 5G coverage both indoors and outdoors.
Three’s coverage map is less sophisticated but fairly comprehensive, yet every coverage map is calculated on estimates of how existing cell tower infrastructure will perform.
They can only predict how strong indoor signals will be, given the immense disparity in scenarios once you venture indoors.
There will be signal strength fluctuations based on the building’s construction, which floor you’re on, whether your device has a protective case and so forth.
The sheer number of people trying to connect can also affect coverage, which is why football stadia tend to be 4G blackspots at half time.
More accurate coverage data is generated by impartial organisations like Opensignal, who collect billions of measurements on a daily basis from 100 million devices worldwide.
They produce detailed active download and upload speed measurements across 3G, 4G and 5G, as well as measuring the quality of voice services and overall network availability.
Ofcom also runs its own mobile coverage checker, calculated using a combination of network data and on-site testing.
If you’re interested to see how your network performs in this regard, visit Ofcom’s checker here.
Band’ of brothers
Although they compete fiercely for custom and dominance, the UK’s big four mobile networks do occasionally work together.
One example of collaboration was announced earlier this year, when they agreed to develop a shared rural network for sparsely-populated regions of the UK.
Each operator has committed to covering 90 per cent of the UK’s land mass by June 2026.
Ofcom will scrutinise this with on-the-ground verification, plus detailed analysis of new on-air sites (and their specifications) cross-referenced against the OSGB grid system.
The UK’s network watchdog will be paying close attention to ensure mobile companies honour their promises in reality, not just on a data map.