5G is available in many UK towns and cities, but coverage is still very patchy. That's because mobile networks have concentrated on enabling a handful of masts in each area. 

However, Ofcom is about to auction off more 5G spectrum to the big four mobile networks, O2, EE, Vodafone and Three. The rules on how this will work reveal that there's a strong impetus on improving coverage outside of main urban areas. 

The main takeaway is that the auction will increase the amount of available airwaves for mobile services by a fifth (18 percent).

Ofcom is releasing 80 MHz of spectrum in the 700 MHz band, following four years of work to clear the band of existing uses for digital terrestrial TV and wireless microphones.

These airwaves are ideal for providing good-quality mobile coverage, "both indoors and across very wide areas – including the countryside." Capacity will also be given a boost as a result. 

Ofcom also aims to give operators the opportunity to create more continuous blocks of 5G spectrum. That's been something Three has been talking up as a competitive advantage - basically because it currently has a 100Mhz block, it's able to provide faster peak speeds. 

This time around, winners of the also-up-for-grabs 120hz of 3.6-3.8 GHz spectrum will be able to negotiate among themselves in terms of where their spectrum sits within the band. This will help networks increase the capacity and speed of their networks. 

As previously announced, Ofcom is imposing a 37% cap on the overall spectrum that any one mobile company can hold following the auction. This should appease the networks that weren't happy about Three's allocation of spectrum last time around. 

All the networks have also committed to delivering good-quality 4G coverage to at least 90 percent of the UK over the next six years.