Sprint plans to use its Magic Box small cell as an aerial radio, relying on the same wireless backhaul that the carrier leverages when it deploys the Magic Box indoors. The company attached a “bare bones” version of the small cell to a tethered drone, and was able to connect to a base station six miles away.
The tethered drones will have two distinct use cases, according to Sprint’s Guenther Ottendorfer, COO for technology. One is enhanced coverage and capacity at events, and the other is cell service in emergency situations and/or natural disasters, which can impair cell sites at the same time that they increase the need for coverage and capacity in the affected area.
Sprint’s test was conducted about 30 miles outside of Dallas and used a drone made by CyPhy Works, which specializes in tethered drones. The tether connects the drone to a mobile generator. Ottendorfer said one of the CyPhy Works drones has remained airborne for two weeks while connected to its power source. He added that the tethered drones can fly as high as 400 feet.
“If you think that you are in an area where there are natural obstacles or buildings, that is quite a good height,” said Ottendorfer. “So we are quite excited that this worked out well.”
Sprint is not the only wireless carrier experimenting with flying small cells. AT&T conducted a similar test in rural Georgia earlier this year. Ottendorfer said Sprint’s unique advantage is its dedicated spectrum.
“If you are up in the air and you are radiating from this elevated point you of course would cause a lot of interference if you don’t have a dedicated channel,” he said. “But with our 2.5 GHz spectrum, we have the possibility to have a dedicated small cell channel.”
Sprint’s Magic Box uses two dedicated channels in the 2.5 GHz band – one to connect to mobile devices and one to connect to a donor site’s base station. The high-frequency radio waves in the 2.5 GHz band do not travel far, but Sprint uses a technology called user equipment relay to connect over longer distances. At each relay station, the signal is demodulated, decoded and retransmitted at its original strength, so signal degradation is minimized.
GCT Semiconductor makes the chip that enables Sprint’s UE relay. Ottendorfer said his company is using GCT’s LTE Advanced GDM7243Q chip, which features 4 receiver/2 transmitter antenna technology. He said the GCT chipset performed very well in the airborne test.
Back on the ground, demand for the Magic Box continues to outpace supply, Ottendorfer said. He expects that imbalance to continue into next year, and said Sprint will continue working exclusively with Airspan to make and supply the equipment. Airspan is a Florida small cell developer that specializes in wireless backhaul. The Magic Box products it supplies to Sprint combine wireless backhaul with Qualcomm’s small cell technology.
Sprint obviously has high hopes for its Magic Box. Back in May when it launched the small cell, the company said it would be a platform for further innovation, and now those plans are taking off. “In this case we can say that there is magic in the air,” Ottendorfer said.
