Japanese group tests 5G at 38 GHz from 4km up

The test forms part of an ongoing Japanese project to roll out a HAPS – or high-altitude platform stations – network and is being described by the companies involved as a major step towards realising 5G from the stratosphere.

At 4km up, the firms are not quite there yet. The aircraft they used to carry the base station kit essentially simulated the eventual use of HAPS. But the test was an important milestone. It set up an aerial relay backhaul link between the Cessna aircraft and three ground stations, using 5G new radio in the 38 GHz band. That last part makes it a world first, the companies said.

Aside from DoCoMo, the companies in question are SKY Perfect JSAT Corporation, the National Institute of Information and Communications Technology (NICT) ,and Panasonic HD. The telco and satellite operators were formally selected for the HAPS project by the NICT at the back end of last year. Panasonic seems to have been added at a later date.

The aim of the project is to develop direct-to-device mobile services delivered via a space-based non-terrestrial network using HAPS. It forms part of the NICT's beyond 5G programme which is all about ubiquitous coverage; it aims to ensure there is coverage over the air, sea and space, regardless of where the user is located.

Phase one of the project is focused on early commercialisation. The firms said they aim to solve various technical issues and demonstrate a communication service using HAPS positioned in the stratosphere over Japan. They are now part way to that goal.

The companies involved in the trial note that the results will help accelerate the practical application of HAPS networks. They are also talking about shooting for "the early delivery of 5G from the stratosphere via an NTN using HAPS," but have not committed to a deadline, at least publicly. Nonetheless, they are clearly pushing hard, so we can probably expect developments to come fairly regularly.

Space Compass, one of the companies involved in the broader project, if not this particular trial, expects to launch HAPS services in Japan in fiscal 2025.

While the trial was about 5G connectivity, the companies also made reference to the ongoing development of 6G mobile and the associated efforts to expand network coverage. Non-terrestrial networks will likely play a significant role in the 6G era, which is shaping up to involve a mixture of network types and technologies, rather than being simply a new cellular standard. R&D endeavours at this stage will position the companies well for the next generation.

6G R&D is high on the list of priorities for Japanese incumbent NTT. The Japanese government recently voted to amend the NTT Law which, amongst other things, required the telco to share and publish the results of its research work. The telco itself campaigned hard for that element of the law to be removed, since it placed it at a disadvantage on the international stage.

But in situations like this, the operator is all too keen to trumpet its successes. NTT and its compatriots are happy to tell their world about their progress in delivering 5G from space.