C Spire and Phazr Complete 5G Trial with Millimeter Waves in Mississippi
C Spire, a privately-held wireless provider that serves the American South, completed a technical trial with Phazr last week at C Spire’s headquarters in Ridgeland, Miss. The goal was to test the startup’s millimeter wave base station technology, which could become a key component of future 5G networks.
Though several national carriers have announced 5G trials in major cities across the U.S., C Spire is a rare example of a regional provider investing in new 5G technology primarily for rural areas.
“When you look at this tech, I think it holds a lot of opportunities for serving that market,” says Stephen Bye, C Spire’s chief technology officer. “We're very bullish about it.”
Millimeter waves are high-frequency waves that fall between 30 and 300 gigahertz, where spectrum remains empty—unlike bands below 6 GHz, which have become crowded with wireless signals. Phazr’s technology, called Quadplex, uses these waves to deliver over-the-air Internet service to homes and businesses within range of a Phazr base station.
C Spire has a problem that it hopes Quadplex can help solve. Though C Spire owns fiber optic cables that run by many rural communities, countless areas still lack broadband service because it’s financially impractical for the company to extend that cable to serve a smattering of households.
“It's just buried gold for a lot of small towns and rural folks,” says Craig Sparks, vice president of technology strategy and planning for C Spire. “We just need to pop it up with solutions that make delivering it quicker.”
In the United States, the average broadband connection delivers data at a clip of 55 megabits per second. But the average Internet speed in Mississippi, which makes up the bulk of C Spire’s service area, is only 26 Mbps.
With Phazr’s technology, C Spire could, in a sense, bring its buried cables to the surface by providing wireless service to homes in the area. Sparks hopes it will allow the company to deliver service with uplink speeds of hundreds of megabits per second to homes that are getting by today on only a fraction of those rates.
A unique aspect of Phazr’s approach is that the company uses only millimeter waves for the downlink carrying data from a base station to its customers. For the uplink, or data sent from customers to a base station, Phazr relies on the traditional cellular frequencies used today.
This strategy has proven popular with wireless providers eager to roll out improved services while 5G standards are still in the works. C Spire, which refers to its work with Phazr as “pre-5G,” sounds particularly optimistic about the company’s ability to help.
“The system’s performing, and we’re seeing the numbers we want,” said Sparks in the midst of the Phazr trials.
For now, Phazr’s setup is only meant to provide wireless service to devices that are inside of a home or other building. The version that C Spire tested does not provide the on-the-go mobile broadband that smartphones require.
A Phazr base station broadcasts signals over millimeter waves to a device called a Gazer that is placed at a customer’s home. The Gazer converts the signal to a lower frequency and then rebroadcasts the signals on Wi-Fi to nearby wireless devices.
To upload data, a device in the home sends it over Wi-Fi to a Gazer mounted on a wall or window, which converts it to a traditional cellular frequency and then sends it back to the Phazr base station.
Sparks says that for C Spire to deploy Phazr’s technology across its network, its base stations would need to be modestly priced and capable of serving customers up to a kilometer away. During last week’s trials, Phazr showed speeds of 250 Mbps as far as a kilometer away from a base station, with a clear line of sight.
Farooq Khan, CEO of Phazr, says he believes the economic sweet spot for any provider to deploy Phazr’s technology will be if they can find areas where the combined cost of installing base stations and providing customers with Gazers works out to be $1,000 or less per subscriber.
When Khan, a soft-spoken former Samsung engineer, first began working on millimeter waves, conventional wisdom in the field held that higher frequencies were cursed with higher signal propagation losses. But Khan realized that, by using directional beams that focus a wave’s energy on one device, such as a Gazer, it’s possible to still deliver reliable service from a distance.
Now, each Phazr base station, called a Rabacks, has 384 millimeter wave antennas and 108 low-frequency antennas that form these directional beams. A Phazr cell site, consisting of three base stations, can support up to 36 beams, which together provide 360-degree coverage.
Rabacks can operate at any frequency between 24 and 40 GHz. For its tests with C Spire, Phazr used 28 GHz. This week, Verizon and Phazr will begin trials near Fort Worth, Texas using Phazr’s equipment at both 28 GHz and 39 GHz. Verizon recently paid $3.1 billion to acquire Straight Path Communications and its spectrum holdings at 39 GHz.
Sanyogita Shamsunder, Verizon’s director of network planning, downplayed the significance of its trials with Phazr in a recent interview. “We test a lot of different technologies in the network,” she says. “It’s routine for us.” She also wouldn’t say what role, if any, Phazr’s tech would have in a series of 11 fixed wireless trials that Verizon will conduct this year.
In one test with C Spire, Phazr six high-definition video streams, at 28 GHz, from a Raback to a Gazer mounted to the inside of a trailer containing six televisions. The Gazer rebroadcast the streams over Wi-Fi to the televisions nearby. Meanwhile, the base station also broadcast an “always on” application, which is an app that runs continuously in the background, to three Gazers. During this test, overall throughput for the network of three Gazers connected to one Raback reached 2.53 gigabits per second.
In a real-world deployment, as more customers, and Gazers, are added to a base station, performance will change. Khan says one Raback maintain download speeds of 1 Gbps to as many as six Gazers at a time in a sparsely populated area, or provide speeds of 100 megabits per second to as many as 60 Gazers at once in a more crowded community. In reality, not all customers use their devices at the same time, so providers often oversubscribe their networks by a factor of five or 10.
Though beamforming has helped Phazr to overcome the signal losses known to plague high frequencies, one thing still stands in the company’s way: leafy trees. Foilage causes higher signal losses for millimeter waves than traditional cell signals, and Khan admits it is a problem.
To avoid as many trees as possible during leafy summers in Mississippi, Phazr plans to attach its base stations to water towers or other tall fixtures in rural areas, and advise customers to install Gazrs high up in their homes for the best service.
“We think if you can put this on top of water towers, those heights are hundreds of feet, we expect the range could be several kilometers,” Khan says.
Khan says even without a clear line of sight, and surrounded by lots of foilage, their base station has delivered hundreds of megabits per second to devices 300 to 400 meters away.
Moving forward, says Khan, Phazr will launch a commercial product for millimeter waves and fixed wireless that will be ready by the second half of 2017. Around the same time, Sparks says C Spire plans to begin trials with friendly users who can test the system’s performance in real-world settings.