Softbank's HAPSMobile, Alphabet's Loon Deliver LTE from Fixed-wing Autonomous Aircraft in Stratosphere

SoftBank’s HAPSMobile and Alphabet’s Loon recently announced they successfully tested their jointly developed communications payload in the stratosphere on HAPSMobile’s “Sunglider,” a solar-powered unmanned aircraft system (UAS). 

Taking place during Sunglider’s first stratospheric test flight at Spaceport America (SpA) in New Mexico on September 21 MT, the test marked the world’s first successful delivery of LTE connectivity from a fixed-wing High Altitude Platform Station (HAPS) autonomous aircraft in the stratosphere.

The stratosphere-ready payload used in the test flight was a first-of-its-kind for a fixed-wing, autonomous aircraft-based HAPS to deliver LTE connectivity. Using MIMO technology, the payload enabled LTE connectivity to be delivered continuously for approximately 15 hours during Sunglider’s test flight. The payload performed as planned in the demanding conditions of the stratosphere, where wind speeds reached greater than 58 knots (approximately 30 meters per second) and temperatures were as low as -73 degrees Celsius.

During the test, the communications payload enabled a video call between Loon members and AeroVironment team members with smartphones at SpA and HAPSMobile team members in Tokyo. The test system was composed of a service link from Sunglider using the 700MHz spectrum band (LTE Band28) and a feeder link between the aircraft and a ground gateway using millimeter wave spectrum*. Since the radio waves transmitted and received by Sunglider operate on the same frequencies as existing smartphones and devices, Loon and AeroVironment members in SpA were able to use regular smartphones to participate in the video call. During the test flight, smooth operations and connection speeds enabled high-definition, low-latency video calls.