UK basestation-in-the-sky startup emerges from stealth

October 20, 2020 // By Nick Flaherty
Basestation-in-the-sky startup emerges from stealth
Stratospheric Platforms Limited (SPL) is developing an electric HAPS high altitude pseudo-satellite with Deutsche Telekom that can provide cellular coverage from the stratosphere.

A UK developer of an autonomous flying basestation has emerged from stealth mode with a key demonstration.

Stratospheric Platforms Limited (SPL) in Cambridge is developing an electric high altitude pseudo-satellite (HAPS) and has successfully demonstrated high-speed 4G connectivity from the stratosphere into a live telecommunications network.

The demonstration of the technology with its largest shareholder Deutsche Telekom (DT) over Bavaria using a remotely piloted H3Grob 520 aircraft at an altitude of 14km (45,000ft) with an LTE antenna, with architecture compatible with 5G standalone. This delivered signals to user equipment at the 2.1 GHz frequency band.  A Voice over LTE (VoLTE) call, video call, data call, and video streaming were demonstrated on a standard smartphone and linked into the DT terrestrial live network with download speeds of 70Mbps and upload speeds of 23Mbps over a 10 MHz bandwidth.

Unlike solar-powered HAPS designs such as the Airbus Zephyr or Facebook Aquila, the SPL platform under development would use a hydrogen fuel cell to provide enough power for the basestation.

The fuel cell has been tested on the ground, and provides 290kW of power, with 20kW for the basestation. The key to acting as a “Mast in the sky” is a massive 9m2 digital steerable phased array antenna with 2048 dual polarisation phased array transceivers. This is equivalent to around 500 terrestrial antennas and even with 4G provides a 5G latency of around 1ms.

The beam steering allows for a configurable cell 100km in diameter that can target areas of low coverage, such as radio ‘shadows’. While the Zephyr or Aquila HAPS can stay aloft for over a year, the SPL platform has a limited mission time of around nine days on its tank of hydrogen.

“This is the worldwide unveiling of Stratospheric Platforms,” said Richard Deakin, Chief Executive Officer of Stratospheric Platforms Limited.

Next: Coming out of stealth

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