mmWave for HAPS: enabling power efficient networks in the sky

A particular class of unmanned aircraft is opening up new ways of providing communication links in hard to reach areas.

Unmanned aircraft have been developed to fly at altitudes of over 70,000ft for up to a year using solar panels. These High Altitude Pseudo Satellites (HAPS) are designed to fly above the weather, carrying surveillance cameras or base station support for public safety applications. Flying from a base to anywhere in the world, these HAPS aircraft can provide communications support, in disaster areas or remote locations, by providing a cellular base station in the sky. These either link to the ground or to another aircraft as they circle over the area.

Several manufacturers are currently investigating such systems. Facebook tested out a system called Aquila, while Zephyr from Airbus and PHASA-32 from BAE Systems have both flown at high altitudes. HAPSMobile, part of Japanese conglomerate Softbank, is also testing a HAPS system called Sunglider in the US.

The possible applications are endless. For public safety, HAPS aircraft can be used to assist with the response to wildfires, floods or oil spills and for tracking large areas of the ocean for pollution, illegal fishing, or piracy. Flying safely over rural areas above commercial airliners they can provide high bandwidth video networks to areas where the coverage is sparse, as well as used for monitoring field and smart agriculture systems and essential infrastructure.

Why the efficiency of mmWave is essential

However, there are significant challenges in the power budget, weight, and providing communications links from the aircraft, as they stay in the air for many months. Powered by solar cells during the day and batteries at night to keep in the same place, there is little power left for the communications links, so highly efficient technology is required.

This is where millimetre wave (mmWave) technology is key for HAPS aircraft, as it supplies a high bandwidth link, either to provide backhaul to the ground for a base station or to carry ultra-high definition video from a camera with a typical power budget of 35 – 50 W depending on range and data rate requirements.

The link can either be direct to the ground or relayed to another HAPS aircraft that can link to the ground elsewhere. This kind of mesh network requires a high bandwidth link, especially for a base station backhaul that handles bi-directional multimedia links.

This has been enabled by recent decisions on spectrum. The unlicensed 57 – 71 GHz band is available in North America and 59-63 GHz is available globally, with the upper bands above 64 GHz less susceptible to absorption by oxygen. This can be used to link HAPS aircraft together as the absorption issues are significantly lower at an altitude of 70,000ft, enabling links up to 100Gbit/s.

Last year’s WARC-19 world administrative radio conference also agreed on the 38-39.5 GHz millimetre wave band that can be used for HAPS systems as well, providing a bandwidth of 1 to 2Gbit/s.

The advantage of the latest mmWave systems is the use of highly power efficient, low latency protocols. Coupled with beam forming technology this provides HAPS system builders with a high bandwidth link that fits within their power budget.

The mmWave platform from Blu Wireless has been designed with the necessary flexibility and performance needed to address a wide range of infrastructure networking applications. Specifically, for HAPS the platform is capable or operating at any mmWave frequency, when integrated with a suitable antenna and radio, and supports a wide range of channel widths, data rates and MAC protocol configurations. The latter is of particular importance for HAPS applications where extended range dictates the need for protocol modifications.

If you’re interested in learning more about this transformative technology and how our mmWave offering can be applied to your connectivity needs, get in touch with us today.