Unlike most epochs, those of the wireless age have come and gone with convenient numerical designations. And with each came marvelous new capabilities: 2G let us all text for the first time, for example, and 3G empowered us to surf the Web.
So now, as phone makers and Internet service providers begin hashing out the details of what 5G will be and how it will work, speculation is high about what new marvels will be possible when carriers can deliver data to smartphones at rates as high as 100 megabits per second [PDF]. Soon, we’ll start to find out: This year, Verizon and AT&T plan to deliver broadband Internet to select homes or businesses using fixed wireless networks built with early 5G technologies. These 5G pilot programs will give the public its first glimpse into a wireless future that isn’t due to fully arrive until the early 2020s.
With 5G, carriers hope to deliver data to smartphone users at speeds 10 times as fast as on today’s 4G networks, and with only 1 millisecond of delay. Right now, standards groups including the International Telecommunication Union (ITU) are in the middle of an eight-year process to set technical specifications and performance parameters for 5G that should be ready around 2020. “At this time, everything is open,” says Colin Langtry, who oversees 5G for the ITU.
For many invested in the 5G rollout, that extended timetable could be a problem. By the time standards are finalized in 2020, carriers and governments will have already poured US $5 billion into 5G development. With so much cash on the line, and facing pressure from data-hungry customers, carriers are moving fast. Over the past year, companies have completed a flurry of lab tests and trials to figure out what types of radios, antennas, and signal processing techniques will work best to deliver 5G in hopes of bringing those technologies and their capabilities to market as soon as possible.
“5G is really an amorphous term,” says Thyaga Nandagopal, a program director for the National Science Foundation who oversees wireless initiatives. “But it’s increasingly going to become very narrowly focused on a few technologies, very fast.”
Both Verizon and AT&T say their 2017 fixed wireless networks will rely on millimeter waves, which are arguably the hottest new 5G technology. Millimeter waves are officially defined as waves transmitted at frequencies between 30 and 300 gigahertz, and they are between 1 and 10 millimeters in length. That’s much shorter than traditional cellular signals, which have frequencies below 6 GHz, typically far below, with wavelengths in the tens of centimeters.
Millimeter waves could solve a big problem for today’s carriers: Customers want to transmit more data at once, but the traditional, sub-6-GHz bands are more crowded than they’ve ever been. In contrast, millimeter waves are part of a wide-open section of spectrum, which offers intriguing possibilities.
In early tests, Verizon homed in on one band in particular—28 GHz,which has become a clear favorite for 5G after the U.S. Federal Communications Commission opened it and a handful of other high-frequency bands for commercial use in July 2016. AT&T, too, has tested millimeter waves at 28 GHz and on another popular band, 15 GHz, at its trial site in Austin, Texas. In the lab, AT&T has achieved peak data speeds of 14 gigabits per second at 15 GHz.
Other companies have also had encouraging results. Last year, Sprintdemonstrated peak data speeds of 4 Gb/s—good enough to stream a virtual-reality demo for spectators—on that same 15-GHz band at the 2016 Copa América Centenario soccer tournament, in Philadelphia. In Japan, NTT Docomo has incorporated another 5G technology called MIMO (multiple-input, multiple output), in which dozens of programmable antennas are made to send and receive signals at once from a single base station, to reach a blazing 20 Gb/s at 15 GHz. At that speed, a complete 2-hour, 1080p, high-definition movie can be transmitted in a second and a half.
Now, Verizon and AT&T are eager to share with customers the speedy data rates they have seen in early tests, despite the fact that comprehensive 5G standards are still years away. But though these two companies may be the first to bring millimeter waves to customers, their fixed wireless networks will fall short of what many experts consider “true” 5G.
Unlike the networks that connect smartphones, fixed wireless systems send a focused beam to connect one stationary point to another, such as a base station to a rooftop antenna. From there, carriers run Ethernet cables from the antenna to deliver broadband Internet to offices or apartments within a building.
To fully achieve 5G, carriers and smartphone manufacturers must also figure out how to deliver high-speed data to mobile users who are riding in cars or trains or walking on sidewalks. And the grandest vision for 5G extends far beyond mobile devices—to autonomous cars, connected appliances, and industrial robots.
There are other problems, too. Millimeter waves don’t easily penetrate obstacles such as buildings, and they are more readily absorbed than traditional microwave cell signals by water and oxygen molecules in the air. So they require more power to travel the same distances as the signals from today’s smartphones. Given these issues, using millimeter waves to serve mobile users will require more sophisticated signal processing and a greater density of base stations than are available today.
Some critics think fixed wireless deployments are an unfortunate distraction at a time when companies should be focused on developing these other capabilities. “Effectively, that’s delaying mobile 5G,” says Paul Struhsaker, chief technical officer for the investment group Carnegie Technologies.
Competitors also warn that Verizon and AT&T may have to forfeit their early fixed wireless investments if other companies turn up even better technologies in time, and industry experts fret about fragmentation across carriers. “The problem with prestandard implementation has always been you risk that your investment after three years is outdated,” says Günther Ottendorfer, Sprint’s chief operating officer for technology.
Still, Sanyogita Shamsunder, Verizon’s director for network planning, says the company will press ahead with its bold 2017 plan for 5G through fixed wireless. “We see a reasonable use case that we think we can address with this technology, so we’re going to do it,” she says.