Early adoption of next-generation network technology in Asia and the US will drive rapid growth in 5G subscriptions, according to the market research team at Ericsson, which expects there will be approximately 150 million 5G cellular subs globally by the end of 2021.

That is just one of many predictions made in the Swedish vendor's latest annual Mobility Report, published early today.

Following the early deployment of pre-standards networks in South Korea and other markets, Ericsson AB (Nasdaq: ERIC) expects commercial 5G networks based on ITU IMT-2020 specifications to be deployed from 2020 onwards. By the end of 2021, the vendor expects 150 million 5G subscriptions, with China, Japan, South Korea and the US experiencing the fastest uptake.

And if 5G does take off that quickly, the uptake will "be even faster than 4G," noted Patrik Cerwall, executive editor of the Mobility Report.

Even so, it would only account for a tiny percentage (about 1.5%) of all mobile subscriptions by that time, if the vendor's total market estimates are accurate (see the graph below).

Figure 1: Source: Ericsson Mobility Report November 2015

But what does Ericsson mean by "5G subscription"? Handily, Cerwall has a definition:

The "new use cases" are mainly related to IoT applications, while "LTE Evolved" and "NX" are terms that Ericsson is using currently to communicate its expectations and view of how networks will evolve -- see the diagram below -- but Cerwall expects standards bodies to agree specific terminology that the whole industry can settle on in the coming years.

Figure 2: Source: Ericsson

The 150 million number comes from Ericsson's own predictive model, which is based on a number of factors including input from all members of the mobile/wireless ecosystem, from chipset vendors to network operators, said Cerwall during a press and analyst briefing in London Tuesday morning. He stressed that the 150 million figure was not an aggregation of 5G subscriber estimates for 2021 from operators.

And while the potential uptake of 5G is interesting, what really matters is the number of total cellular subscriptions -- an estimated 9.1 billion, up from 7.4 billion this year -- and even more importantly the volumes of data traffic running over those connections, which according to Ericsson's estimates is set to grow by more than tenfold between 2015 and 2021 to more than 50 Exabytes per month, of which almost 70% is expected to be video (see chart below).

Figure 3: Source: Ericsson Mobility Report November 2015

For those of you, like me, who can't recall how an Exabyte relates to other measures of data storage, it is the equivalent of 1 billion Gigabytes: Here's a handy guide (using decimal multiples):

Or put another way, 1 Exabyte would store the content of 33 million Blu-ray disks of the film Jurassic Park. So that's a lot of data.

What that means is that the companies running and operating the networks supporting that traffic need to think just as much about how they are going to transport, deliver, analyze and bill for all that data: That, really, is the big issue facing network operators in 2021.

— Ray Le Maistre, , Editor-in-Chief, Light Reading