UK market leader EE expanded its 5G trials to nine additional sites in London, making the announcement on the same day rival 3 UK outlined plans to invest £2 billion in the technology.

In a statement, EE said the trial will now cover some of the busiest parts of east London, while also revealing details on its learnings from 5G testing so far.

EE’s first 5G trial went live in London’s Canary Wharf last month. The BT-owned operator said initial assessments had encompassed “every element of building a new 5G network”, including obtaining planning permission and access agreements, to managing power outlets.

Further tests planned include evaluating the customer experience of 5G-suitable spectrum, with businesses and consumers in the areas invited to test the technology. It added the first use of its 5G offering is intended to be an alternative to fixed-broadband.

As well as revealing it has beefed up trial sites, the company also highlighted a number of challenges it will need to overcome when deploying 5G.

EE said upgrading 4G was often easy by repurposing existing antennas, but adding new equipment to each site “is essential to 5G”.

This meant additional rooftop sites needed “significant strengthening” to carry new 5G antennas due to their weight (50kg) and the fact each location could require three antennas.

In addition, the level of upgrade work caused delays in obtaining planning permission and necessitated additional work, while location for 5G antennas can also be dictated by the need to stay below government-regulated power output levels.

BT CTIO Howard Watson said deploying “this brand new layer of our EE mobile network is far from straightforward”, and the trial helped it understand and overcome challenges it expects in the coming years. “We’re also learning about the coverage we can achieve with 5G New Radio on our new 3.4GHz spectrum, both indoors and in densely cluttered streets,” he added.

EE previously stated it aims to be first UK operator to roll-out 5G, with a planned launch in 2019.

Rival 3 could, however, provide some competition: the investment it announced forms part of a goal to also launch 5G in 2019.