Facebook approaches 20Gbps on millimetre-wave link
Facebook has claimed a record data rate over a millimetre-wave link, with its Connectivity Lab stating today that it almost hit 20Gbps on a 13km link in Southern California earlier this year.
Making the announcement in a blog post, the company said it had used custom componentry that used 2GHz of bandwidth and sucked only 105 watts of DC power at the transmitter and receiver.
The ultimate goal of the Connectivity Lab's research is to be able to use solar-powered drones, named Aquila, to deliver 30Gbps across a range of 30 to 50 kilometres. The company said it is looking at millimetre wave due to a large amount of available continuous bandwidth in the 30GHhz to 300GHz range, but it has to address the issues of atmospheric absorption of the waves, the narrow line-of-sight beam and antenna challenges, and power issues.
"The 4-ft antenna is representative of the ground station in an air-to-ground link. In practice, it must be able to track moving transmitters on the airborne Aquila fleet continuously, with high precision and high accuracy to maintain uninterrupted high data rates," Facebook said.
"In our setup, the 3-dB beam width of the 4-ft antenna is around 0.2 degrees, and to achieve the nearly 20 Gbps data rate, the antenna needed to be pointed with an accuracy better than 0.07 degrees. This is equivalent to a baseball pitcher aiming for a strike zone smaller than the size of a quarter."
Facebook is currently testing its air-to-ground bidirectional link equipment on a Cessna plane being flown at altitudes up to 20,000 feet. The company expects to have gear capable of 40Gbps early in 2017.
The company's Aquila unmanned aerial vehicle has the wingspan of Boeing 737, and is set to remain at an altitude of 60,000 to 90,000 feet for up to 90 days to deliver internet connectivity to remote regions.
Mike Schroepfer, Facebook's chief technology officer, called Aquila a backbone in the sky earlier this week.