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Softbank's Cylindrical Antenna for HAPS to Reduce Handovers

One of the challenges with HAPS or even tethered balloon is that when the balloon or HAPS turns, the cells change position and this can result in handovers even for users that are stationary. This unnecessary signalling can be reduced, as Softbank explained, with an innovative antenna designed to reduce these.

Softbank shared this news last year while its subsidiary HAPS Mobile shared a video here. Quoting from the article:

People are able to use their mobile phones when they’re on the move, such as when they’re riding in cars and trains, for example.

They can do this thanks to what’s called the “handovers.” In the handover process, when a mobile phone moves further away from a base station and the signal becomes weak, it automatically connects to another base station from which it can receive a stronger signal.

With HAPS, the airborne base station moves continuously while the receiver stays stationary, and this causes handovers. A HAPS aircraft delivers network connectivity with radio beams as it circles the sky. But this means that the communication area on the ground (i.e., the footprint) also changes in tandem with the airborne vehicle’s movements and the direction of the radio beams. A mobile phone or device switches cells (i.e., handovers occur), and reception strength can greatly fluctuate. This negatively impacts telecommunications quality.

To solve this problem, “footprint fixation technology” is necessary. Footprint fixation technology secures the direction of radio waves beamed to the ground and prevents communication area switching, even as a HAPS vehicle rotates.

To achieve footprint fixation technology, SoftBank and its subsidiary HAPSMobile led the world in developing what’s called a “cylindrical antenna.” The antenna has a distinctive form with multiple antenna elements wrapped around it in the shape of a cylinder.

By controlling each antenna element individually, it’s possible to direct the radio beam (cell) in any desired direction. By constantly transmitting the radio beam to the same specific area on the ground as a HAPS aircraft rotates, the communication area (footprint) can be secured.

In this way, footprint fixation technology makes it possible to provide from the sky the stable connectivity that is essential for telecommunication services.

You can read further details here or the press release here.

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