The boom in the number of mobile Internet devices and tablet computers in use will help quadruple Web traffic in the coming years, a study said Wednesday.

The Cisco Visual Networking Index said global Internet traffic by 2016 will be 1.3 zettabytes. A zettabyte is one trillion gigabytes, or one sextillion bytes.

That will be four times the level of traffic generated in 2011, according to Cisco, and comes from a proliferation of tablets, smartphones and other devices that use the Internet.

"Each of us increasingly connects to the network via multiple devices in our always-on connected lifestyles," said Cisco vice president Suraj Shetty.

"Whether by video phone calls, movies on tablets, web-enabled TVs, or desktop video conferencing, the sum of our actions not only creates demand for zettabytes of bandwidth, but also dramatically changes the network requirements needed to deliver on the expectations of this new normal.'"

By 2016, the forecast projects there will be nearly 18.9 billion network connections, or nearly 2.5 connections for each person on earth, compared with 10.3 billion in 2011.

It also cited United Nations estimates that there will be 3.4 billion Internet users by 2016, or about 45 percent of the world's projected population.

The average fixed broadband speed is expected to increase nearly fourfold, from nine megabits per second (Mbps) in 2011 to 34 Mbps in 2016.

Cisco also said that by 2016, over half of the world's Internet traffic is expected to come from Wi-Fi connections.