UK mobile operator Everything Everywhere, the joint-company created after the merger of T-Mobile and Orange, has announced that it plans to invest £1.5bn over the next three years in upgrading its mobile networks, reports Reuters.

Throughout 2012, Everything Everywhere will seek to further integrate the two companies under its stewardship, meaning that more Orange and T-Mobile customers will be able to use the 2G and 3G signals from each network, which we reported back in October.

Everything Everywhere say that the investment and upgrade will help kick-start its preparations for 4G, which will give mobile users faster access to Internet on their mobile devices. Olaf Swantee, Chief Executive at Everything Everywhere, said.

“With mobile data increasing 250 percent over the past two years, we are making these investments so we can deliver on our ambition to provide the UK’s most reliable, biggest and best mobile data network. We believe that the UK requires a 21st century infrastructure and are committed to rolling out 4G as soon as possible to support growing data use, connect parts of the country with little or no mobile broadband, and drive economic growth.”

In the early part of 2012, Everything Everywhere will make moves to improve the signal-sharing across the networks, by letting Orange and T-Mobile customers’ devices automatically tap-in to whichever network has the strongest signal where a user is.

Back in November, we reported that Everything Everywhere had been required by the EU to sell extra spectrum as a result of the merger between T-Mobile and Orange, to help increase competitiveness with its rivals. We speculated that this could well see investment in reinforcing its 3G and HSPA+ networks to increase coverage and signal strength throughout the UK. With a delay in the auction for 4G spectrum, the company wasn’t able to begin a full rollout of 4G services until it was clear what bands it would operate on within the UK.

UK communications regulator Ofcom has yet to publish the final terms for the auction, which is looking like won’t happen until into the new year now.

Everything Everywhere has said that customers of both its networks should see coverage improvements in the coming weeks.