If unlicensed Wi-Fi spectrum is like a cool, independently run cafe, then mobile operators using those frequencies for LTE may sound like a corporate chain buying out your favorite spot.
There goes the neighborhood. Or does it?
LTE is coming to the fat 5GHz unlicensed radio band that much of consumers' Wi-Fi use now depends on. The idea drew skepticism at first, but the mobile industry is starting to agree on some steps to make sure wireless LANs don't get trampled under LTE's feet. The first trial deployments are expected to begin this year, and users could get faster service as the technology is rolled out.
Huawei and NTT DoCoMo demonstrated the technology last August, Qualcomm showed it off at International CES last month, and T-Mobile USA plans a trial deployment later this year. More plans for unlicensed LTE may be revealed next month at Mobile World Congress in Barcelona, where the quest for more mobile capacity will be a hot topic.
LTE was designed to run over frequencies exclusively licensed to mobile operators, for which some carriers have paid billions of dollars. In its current form, LTE lacks crucial features to prevent one type of network from drowning out others in unlicensed spectrum.
That would seem to make LTE a poor fit for unlicensed bands. But growing demand for cellular capacity can make mobile operators act a little crazy: In the U.S. last week, the Federal Communications Commission tallied up more than US$40 billion in bids for new cellular spectrum. Most carriers are also turning to Wi-Fi, a completely different technology from cellular, even though they need to adopt new technologies to automatically move subscribers between the two systems.
In that light, sending LTE signals over unlicensed frequencies doesn't look so outlandish. In the 5GHz band, there's more than 400MHz of unlicensed spectrum available in most countries. That's more than most mobile operators have in all their licensed bands combined. No one will be able to use all 400MHz at one time, but an average subscriber who walks into range of an unlicensed LTE cell might get twice as much spectrum, according to Tolaga Research analyst Phil Marshall. And more bandwidth typically means more speed.
Using that deep well of spectrum without giving up the familiar controls and guarantees of a cellular network was what early proponents of unlicensed LTE, such as Qualcomm, had in mind. LTE is also tuned to use spectrum more efficiently than Wi-Fi does, proponents say. But the concept was controversial when it was first proposed at 3GPP, the standards body that oversees LTE.
Wi-Fi users already face crowded airspace in some areas, often the very kinds of mobile meccas where carriers might deploy unlicensed LTE: business districts, convention centers, and hotels. The idea of letting LTE networks use the same, already taxed spectrum raised alarm bells for some in the industry, especially carriers that use Wi-Fi to supplement their networks.
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