STOCKHOLM (Reuters) - Global subscriptions for smartphones will almost double by 2022, helping mobile data traffic to eightfold, telecoms network gear maker Ericsson predicted on Tuesday.

The Swedish company said it expected there will be 6.8 billion smartphone subscriptions globally by the end of 2022, up from 3.9 billion in 2016.

In its previous forecast from June this year, Ericsson had said it expected 6.3 billion smartphone subscriptions by the end of 2021.

Ulf Ewaldsson, head of strategy and technology at Ericsson, said the biggest change from its previous report was the jump in 5G subscribers to 550 million in 2022 from 150 million in 2021.

"We predict that 25 percent of those will be in North America and 10 percent in Asia," Ewaldsson told Reuters.

The first 5G networks will be launched at the end of 2017 and Ericsson plans to sell 5G equipment on a "larger scale" in 2018, Ewaldsson said.

Ericsson said mobile data traffic continues to grow, driven by an increase in smartphone subscriptions and data volume per subscription, fueled primarily by more viewing of video content.

Ericsson plans to boost efficiency and technology to deal with an expected increase of mobile data traffic of around 40 to 50 percent per year despite roughly flat infrastructure investments by telecom operators, Ewaldsson said.

(Reporting by Olof Swahnberg and Helena Soderpalm, editing by Mia Shanley)