Carrier says multiple input, multiple output antennas are increasing capacity by 300%
Sprint and Samsung are preparing to deploy dozens of antenna elements per cell site in select areas across the U.S., as the carrier rolls out massive MIMO to leverage its 2.5 GHz spectrum in preparation for 5G. The two companies have been testing the technology in Suwon, South Korea and Sprint said it has been able to increase channel capacity by at least 300% and boost cell edge performance by 200%.
“The performance that we’re seeing is very encouraging: peak speeds of more than 300 megabits per second just using one 20 megahertz channel,” said Sprint CTO John Saw. “To get that sort of performance using a more traditional 8 transmit, 8 receive base station that we have deployed today, you need to do three channel carrier aggregation. But with massive MIMO simply on just one channel, we were able to reach peak speeds of more than 300 megabits per second and when we do three carrier aggregation on top of this massive MIMO antenna we should be going past the gigabit per second capability.”
Sprint has already demonstrated “gigabit class” LTE on a commercial network. The carrier showcased the technology in New Orleans earlier this year. Sprint used three channels (60 megahertz) of its 2.5 GHz spectrum, as well as four-channel MIMO antenna technology and 256 quadrature amplitude modulation. That demonstration used a forthcoming Motorola handset powered by Qualcomm’s Snapdragon X16 LTE modem. But according to Sprint and Samsung, users will not need to use a state-of-the-art smartphone to enjoy the benefits of massive MIMO since radios that can transmit and receive on 64 channels split capacity between multiple end user devices within a sector.
“There is no handset dependency here,” said Lyle Nyffeler, VP and GM of the networks division at Samsung Electronics America. “When Sprint rolls this out on their infrastructure there is not necessarily a specific handset users have to have, so all users get some lift from this. … You’ll see capacity increase up to 8 times over current technologies.”
Roll out planned for next year
Saw said Sprint plans to roll out massive MIMO next year in the U.S., deploying Samsung radios with up to 128 antenna elements at cell sites that need more capacity. He said that because the antenna elements are so small, they can be tightly integrated with the radios, meaning that the carrier will not purchase separate antennas from other vendors.
“We are expecting to get the fully equipped system from vendors like Samsung,” said Saw. Sprint also works with infrastructure vendors Nokia and Ericsson, and has conducted massive MIMO tests with Nokia. But Saw said Samsung has a unique advantage.
“Samsung is unique because not only do they provide the infrastructure, but they also have some really cool handsets,” said Saw. Samsung’s Galaxy S7 phones were the first to leverage 4×4 MIMO. Smartphones that are equipped with multiple antenna elements should benefit the most from massive MIMO, although the technology is expected to boost capacity for all users.
Since most smartphone use occurs indoors, boosting capacity for all users means improving the in-building experience. Sprint said its massive MIMO technology transmits vertically as well as horizontally, meaning that a rooftop antenna could potentially improve the experience of users on the floors below. Saw said that the small antennas Sprint is using are well-suited for rooftop deployments.
Saw said the 300 Mbps per channel downlink speeds that Sprint and Samsung achieved on the streets of Suwon were complemented by faster uplink speeds and better overall coverage. “When you have so many antennas not only can you transmit more, you can listen better on the uplink,” Saw said.
Spectrum advantage
Sprint has slipped into fourth place nationwide in terms of overall subscribers, and the company is banking on its unique spectrum portfolio to turn things around by creating a superior network. Sprint’s 2.5 GHz spectrum uses smaller radios and antennas than those used in low-band spectrum, so Sprint should have an advantage over its competitors when it comes to deploying massive MIMO.
“Massive MIMO is a tremendous differentiator for Sprint because it is easily deployed on 2.5 GHz spectrum due to the small form factor of the radios needed for a high-frequency band,” said Günther Ottendorfer, COO for technology at Sprint. “In lower frequency bands, wavelengths are much longer and therefore the radios require much larger, impractical form factors.”
“If you try to do this at 700 MHz, for instance, it is going to be the size of your car,” added Saw. “Even with all these antennas [our equipment] is still smaller than a typical 700 MHz antenna.”
Sprint’s 2.5 GHz spectrum is also well-suited for network densification, and the carrier has been working for more than two years to try to deploy small cells in cities all over the U.S. Most recently Sprint announced an indoor small cell solution called the Magic Box, which it said will boost capacity in buildings as well as in nearby outdoor areas. Sprint wants to use wireless backhaul for its small cells, and said that the Magic Box units will employ user equipment relay. According to Saw, Sprint intends to use massive MIMO for UE relay for all its small cell deployments.
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