The main worry was that service providers would build LTE networks, without any coexistence mechanisms, that relied totally on the "free" unlicensed frequencies in 5GHz, said Tom Peters, an engineer at law firm Hogan Lovells and a former chief engineer of the Wireless Bureau of the FCC. Wi-Fi is designed to "back off" when it senses another device using a channel, but this feature assumes that other technologies in the unlicensed band will treat it the same way.
"If somebody were to deploy unlicensed LTE as a stand-alone service in an unlicensed band, you very likely wouldn't be able to use Wi-Fi," Peters said.
However, unlicensed LTE was really conceived as a way to supplement regular licensed LTE networks, he said. Backers of the technology eventually agreed to change its name to LAA (Licensed Assisted Access) to reflect this. "That calmed a lot of people down," Peters said.
3GPP plans to include features in the next version of LTE, due to be finished around the end of this year, to help it coexist with other networks in unlicensed bands. And though different countries have different rules in this area, all unlicensed LTE products should be safe for Wi-Fi.
Ericsson, one of the world's largest mobile equipment makers, will build its gear to meet the demands of its customers in each market, said Eric Parsons, head of mobile broadband LTE at Ericsson. But all of its equipment will coexist peacefully with Wi-Fi, meaning that adding an unlicensed LTE cell won't have any more effect than adding another Wi-Fi access point, he said.
Parsons and other backers of LAA say it will do more for subscribers than the Wi-Fi services many carriers offer today. Rather than be handed off from one network to another, users will stay on the cellular network, so calls and data sessions are more likely to stay up without a glitch, they say.
"The handoff between any network boundary is a pain, and it often results in failures due to latency," Tolaga's Marshall said. "You don't want to be doing that if you don't have to."
Cisco Systems, which sells Wi-Fi gear to carriers around the world, says there's no difference. Its systems already allow carriers to manage unlicensed spectrum as if it were licensed, according to Kelly Ahuja, Cisco's senior vice president of service provider products and solutions. But the company is agnostic when it comes to the two technologies, he said.
Vendors, carriers and service providers have worked long and hard to make roaming among Wi-Fi networks or between cellular and Wi-Fi as seamless as possible. So-called Hotspot 2.0 technology, as well as parts of the LTE standard allowing handoffs between cellular and Wi-Fi, are gradually being implemented in devices and networks.
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