The much-anticipated 5G mobile standard won't be finished until 2020, but the people who'll make it happen were busy throughout 2015 trying to define it.
One thing that's clear already is that 5G won't be like 4G. Rather than just making phones and tablets faster, the next generation of mobile technology will be asked to serve many uses, each with different requirements.
This was a year for sorting through those demands.
"A lot of progress has been made," said Tolaga Research analyst Phil Marshall. "Effectively, we're trying to find the right set of technologies to use."
While the needs are abundant, the choice of possible ways to meet them is also wider than ever. Ultra-high frequencies that until recently were considered impossible to use for mobile services could deliver much higher speeds. Emerging systems that can send data across the network in a trickle may let Internet of Things devices last years on tiny batteries. And researchers are working on reducing delays so messages we need for tasks like driving can be delivered on time.
Rest assured that 5G will be faster than 4G. This year, everyone had something different to say about how much faster. Ericsson said it had achieved 5Gbps on a testbed for 5G, surpassing the fastest LTE networks by about 50 times. Samsung demonstrated potential 5G technologies running at 7.5Gbps and got a stable 1.2Gbps signal to a minivan traveling at highway speed. The European Commission's 5G Public-Private Partnership set a goal for the new standard of 100 times faster than 4G, and Japanese carrier NTT DoCoMo said it planned to achieve that kind of speed (10Gbps) in partnership with vendors including Ericsson, Alcatel-Lucent, Nokia and Samsung.
Samsung demonstrates 1.2Gbps data transmission over a prototype 5G wireless network to a vehicle traveling at 100kmph
But making mobile faster will take more than better radios and antennae. Operators will also need more spectrum, which will bring government decision-making into the mix. The U.S. Federal Communications Commission started down the path to opening up some promising new bands this year, recognizing that process could take a long time.
Faster, by itself, won't be enough for 5G. It needs to go slower, too. It will have to connect the growing Internet of Things, where devices like sensors and meters won't have much data to send but will have to fit in tight spaces and last longer on batteries. Dedicated narrowband networks for IoT gained ground in 2015, and the developers of 5G want to make sure the future standard can play, too.
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