The hottest item at Mobile World Congress won't be for sale

Commercial mobile operators, which for years relied on exclusive frequencies doled out through auctions or competitions, are now looking toward bands that anyone can use. Not only is unlicensed spectrum free, it may also become available with less time-consuming red tape. And there's a lot of it.

Consumers choose unlicensed spectrum every day when they let their phones switch over to Wi-Fi at home or in a coffee shop. (Wi-Fi is the biggest unlicensed success story.) Carriers encourage this because it means less traffic on their cellular networks. But there are a lot of other ways in which cellular devices, as well as the Internet of Things, are starting to take advantage of this kind of spectrum.

Unlicensed spectrum isn't a free-for-all, but it lets innovators put new kinds of networks and devices on the air as long as they don't keep others from using the band. The frequencies are not the same  in every country, but some bands are close to universal.

Here's what unlicensed spectrum could do for you at Mobile World Congress:

Faster 5G

5G will be a hot topic at MWC, and for the major carriers and vendors that means going higher up the spectrum chart. Cellular networks have never used spectrum above 6GHz, partly because range is short up there. But the 5G promises they're making, like 100 times the average throughput of LTE, may require so-called millimeter-wave frequencies. There are big chunks of spectrum practically unused in these bands, some of which, like 60GHz, are unlicensed.

Last year, Nokia and NTT DoCoMo demonstrated a 70GHz small cell -- in a sealed room on the show floor -- that could follow a moving radio simulating a pedestrian's phone. The dial in that demo read 2Gbps (bits per second), and Nokia says since then it's reached 19Gbps with millimeter waves. 

AT&T, Verizon, SK Telecom and other carriers plan to use millimeter waves in test networks of proposed 5G technologies, starting as soon as this year. The U.S. Federal Communications Commission wants to make such bands available for mobile service and is considering a range of options, including unlicensed use.

IoT networks

Unlicensed spectrum is a key part of a challenge to cellular being led by service providers that specialize in IoT. So-called LPWAN (low-power wide-area network) technologies will be a hot topic at MWC. These networks are designed to cover wide areas and reach thousands of devices like sensors and meters without draining their batteries.

With unlicensed spectrum, LPWAN companies can roll out networks more quickly and less expensively, tap into mass-produced chips for devices and go international more easily. One prominent player is SigFox, which has built a network across France, supplied its technology to operators in Spain and other countries, and is building infrastructure in the U.S. It uses the 900MHz band, where there are unlicensed frequencies in many countries. Another LPWAN company, Ingenu, uses the unlicensed 2.4GHz band. Both will announce expanded coverage at MWC.

Better 4G

The 5GHz unlicensed band that's made it possible for Wi-Fi to reach gigabit speeds is so attractive that cell carriers are taking a close look at it.

Most mobile operators have already turned to Wi-Fi networks to reduce the load on their cells. But after years of refinements to the hand-off process, it can still be a chore for both subscribers and carriers, said analyst Peter Jarich of Current Analysis. The next step is to integrate cell networks into the unlicensed spectrum.

This was already happening at last year's MWC. At the time, it looked like Wi-Fi and cell operators might find ways to get cozy in this band, a huge swath of spectrum that most new Wi-Fi networks rely on. What happened next dispelled that notion.

Unlicensed LTE, the most intriguing new idea on the scene last year, is now in the middle of a storm that's just starting to show signs of clearing. It's a set of technologies that let 4G cellular networks use unlicensed frequencies in this band. Some Wi-Fi advocates say unlicensed LTE will squeeze out current users of the 5GHz band that Wi-Fi relies on. Charges have flown back and forth for months. Standard tests for compatibility may make both sides happy, but they're still under development.

Vendors aren't standing still while that gets hashed out. Verizon and T-Mobile USA, plus South Korean carriers, want to use it. At MWC, Qualcomm, the biggest unlicensed LTE backer, will be showcasing the technology in its newly announced X16 LTE modem. The X16 is Qualcomm's first to include the version of unlicensed LTE for Japan and Europe, with extra safeguards built in, along with the type that carriers in Korea, the U.S. and China are pursuing.

Those systems use 5GHz as an add-on to a licensed network. Another form of the technology, called MulteFire, is a standalone LTE small-cell network that doesn't use any licensed spectrum. The MulteFire Alliance industry group will officially launch at MWC, with member companies including Ericsson, Nokia and Ruckus Wireless.

Yet another technology, LWA (LTE-Wi-Fi Link Aggregation), would let a user connect to both Wi-Fi and LTE networks and enjoy the bandwidth of both in one virtual connection. This could be done in software and wouldn't send LTE signals into the unlicensed band. Alcatel-Lucent showed it off last year and Nokia, its new parent company, is still pursuing the technology and will demonstrate it at the show. But LTE-U is getting far more attention from carriers.