Millimeter waves, massive MIMO, full duplex, beamforming, and small cells are just a few of the technologies that could enable ultrafast 5G networks providers are experimenting with broadcasting on millimeter waves, which use higher frequencies than the radio waves that have long been used for mobile phones.
Millimeter waves are broadcast at frequencies between 30 and 300 gigahertz, compared to the bands below 6 GHz that were used for mobile devices in the past. They are called millimeter waves because they vary in length from 1 to 10 mm, compared to the radio waves that serve today’s smartphones, which measure tens of centimeters in length.
Until now, only operators of satellites and radar systems used millimeter waves for real-world applications. Now, some cellular providers have begun to use them to send data between stationary points, such as two base stations. But using millimeter waves to connect mobile users with a nearby base station is an entirely new approach.
There is one major drawback to millimeter waves, though—they can’t easily travel through buildings or obstacles and they can be absorbed by foliage and rain. That’s why 5G networks will likely augment traditional cellular towers with another new technology, called small cells.
Small cells are portable miniature base stations that require minimal power to operate and can be placed every 250 meters or so throughout cities. To prevent signals from being dropped, carriers could install thousands of these stations in a city to form a dense network that acts like a relay team, receiving signals from other base stations and sending data to users at any location.
While traditional cell networks have also come to rely on an increasing number of base stations, achieving 5G performance will require an even greater infrastructure. Luckily, antennas on small cells can be much smaller than traditional antennas if they are transmitting tiny millimeter waves. This size difference makes it even easier to stick cells on light poles and atop buildings.
This radically different network structure should provide more targeted and efficient use of spectrum. Having more stations means the frequencies that one station uses to connect with devices in one area can be reused by another station in a different area to serve another customer. There is a problem, though—the sheer number of small cells required to build a 5G network may make it hard to set up in rural areas.
In addition to broadcasting over millimeter waves, 5G base stations will also have many more antennas than the base stations of today’s cellular networks—to take advantage of another new technology: massive MIMO. See link for article and video: http://spectrum.ieee.org/video/telecom/wireless/everything-you-need-to-know-about-5g