Fujitsu Laboratories Ltd. has developed the world's first equipment technology to enable simultaneous communications to four users with a single antenna panel in the 28-GHz band, in a compact structure.

The equipment delivers high-speed communications in excess of 10 Gbps, as required by 5G mobile communication formats.

While 5G can provide high-speed, high-capacity communications in excess of 10 Gbps, its radio waves are very one-directional and blocked by obstacles. As such, the use of a method called small cells, in which base stations are deployed every few tens of meters, is anticipated. Commercialization also requires compact equipment that can be easily installed in any location.

5G base stations make use of a technology called beam-forming, which controls the phase of signals emitted from the multiple antenna elements on the antenna panel and concentrates the radio waves in the desired direction. This divides and multiplexes beams, to handle simultaneous communications with multiple users.

Currently, to avoid radio wave interference during communications with multiple users at once, base stations have been configured to use a number of antenna panels corresponding to the number of concurrent users. To miniaturize the equipment so that it can be deployed anywhere, the best option is to provide multi-directional transmissions from a single antenna panel.

Fujitsu Laboratories developed a phased array chip using a technology (patent registered) that can regulate the phase of a signal propagated from an antenna element with accuracy of one degree or less, and built into the panel one phased array chip per eight antenna elements. The company also uses circuitry that detects the differences in phase between phased array chips, which enables highly accurate phase control for any size antenna panel that has between 64 and 256 antenna elements. As a result, by holding the difference in undesired emissions intruding between one radio wave communicating with a device and another radio wave with another device to 20dB or more, it makes it possible for a single antenna panel to carry out high-capacity communications of 10 Gbps or more.

Detecting the phase differences from the signals produced by each antenna element and controlling the phase with high accuracy to concentrate the signal in the desired direction, these technologies successfully led to compact equipment that transmits to four users simultaneously with just one antenna panel. The compact equipment propagates radio waves on two axes, including horizontal and vertical directions, enabling wide-area communications with users.

These technologies led to the prototyping of a 13 cm2 antenna panel equipped with 128 antenna elements and 16 phased array chips. Accordingly, Fujitsu Laboratories confirmed that a single antenna panel can deliver high-speed transmissions of 2.5 Gbps per person, for a total of 10 Gbps, and carry out beam multiplexing in four directions. By using this antenna panel, it will be possible to build small, energy efficient 5G base stations.

Fujitsu Laboratories will continue to increase the performance and reliability of this technology, and aim for commercialization around 2021.