KDDI and Kyocera Succeeded in Developing Wireless Relay Technology That Dramatically Expands Millimeter-Wave Coverage Japan Innovation 5G Alliance/Collaboration

Tokyo and Kyoto - January 23, 2025 - KDDI Corporation (President, Representative Director, CEO: Makoto Takahashi; 'KDDI') and Kyocera Corporation (President, Representative Director: Hideo Tanimoto; 'Kyocera') today announced that for the first time in the world, they had developed a new wireless relay technology that dramatically expands the millimeter-wave (28GHz band) coverage in urban field testing, significantly enhancing the potential of 5G communications¹. This new technology implemented in miniaturized repeaters was deployed in Tokyo's Nishi-Shinjuku area in October 2024, and initial testing tripled the millimeter-wave street coverage from 33% to 99%, compared to the absence of repeaters. Testing will continue through March 31, 2025, toward a goal to commercialize this technology within 2025 for stable, high-speed communication in dense service areas such as urban centers, transit stations, and stadiums.

Repeaters employing the KDDI/Kyocera technology enable the formation of a network in a mesh pattern autonomously to expand the coverage area. This solution replaces the conventional concept of independent "transmit" and "receive" functions of repeaters by dynamically switching roles between transmission and reception and adapting seamlessly to the wireless environment. This realizes autonomous and continuous coverage area formation in collaboration with other millimeter-wave base stations.

Repeater Installation in Nishi-Shinjuku Area

Wireless Relay Technology to Expand Millimeter-Wave Area

Expanding Street Coverage from 33% to 99% Before and After Repeater Installation
Created by KDDI based on a map from the Geospatial Information Authority of Japan

With its high-speed communication capabilities, the millimeter-wave band holds immense potential for expanding 5G deployment, especially in high-traffic areas such as railway platforms, stadiums, and meeting points. However, due to the strong directivity of millimeter-wave signals and their susceptibility to interference from buildings and trees, when antennas are installed on building rooftops, as is the case with other frequency bands, the millimeter-wave coverage tends to be formed in small, scattered areas, requiring significant investment in base stations for continuous and dense deployment. Overcoming these challenges is crucial to unlocking the full potential of millimeter-wave technology.

This technology enables the repeater to autonomously form a relay network for the received base stations and efficiently expand the millimeter-wave area. Repeaters implementing this technology collaborate with each other and are connected in a mesh pattern, making it possible to dramatically expand the millimeter wave area.

The KDDI/Kyocera repeater requires only a power supply and does not require backhaul lines, offering easy installation and low operating costs. Its miniaturized enclosure and lightweight simplify network expansion by allowing installation on existing infrastructure, including streetlights.

During the field testing, 22 repeaters were installed on streetlights and underground transit entrances owned by the Tokyo Metropolitan Government and Shinjuku Ward, utilized under the "Connected TOKYO" framework to promote 5G². Testing began on October 29, 2024, and confirmed that street coverage tripled from 33% to 99% compared to the absence of repeaters in an approximately 600-meter square area in the Nishi-Shinjuku district.

■ New Repeater Benefits

Autonomous Area Formation
In conventional relay technology, antennas are designated as donor sides for receiving signals from base stations and service sides for transmitting. Area construction requires adjusting the roles and direction of each antenna. In contrast, this relay device allows each antenna to dynamically switch between donor and service functions, with the antenna receiving signals from the millimeter-wave base station acting as the donor side and the other antennas as the service side. This enables efficient millimeter-wave area formation and expansion, with devices interconnecting in a mesh pattern.
This feature eliminates the need for role adjustments and antenna alignment, offering greater installation flexibility and simplifying construction design.

Comparison of Conventional Relay Technology and New Wireless Relay Tech with Mini Repeaters

Optimizing Relay Routes
The new repeaters select the relay route with the best signal quality among millimeter-wave signals from multiple directions, forming a network in a mesh pattern. The repeaters detects signal deterioration from the base station and other repeaters, instantly calculating the optimal relay route and switching. If one relay route is inhibited by environmental changes, such as the construction of buildings, trees, or large trucks blocking the signal, the repeaters continuously select more optimal relay routes.

Optimization of Relay Routes

Compact and Lightweight
The new KDDI/Kyocera repeaters measure just 216mm x 216mm x 246mm and weigh only 4.9kg. Compared to conventional millimeter-wave base stations, they reduce size and weight by about 70%. This simplifies installation by allowing a new range of existing-mount options, including streetlight infrastructure, minimizing impact on the landscape and environment.

Please refer to the attached document for details on the field test.

＜Attached Document＞

■About the Field Testing of This Technology

1．Overview

・To confirm the effect of expanding the millimeter-wave area with these repeaters, field tests were conducted by installing repeaters on assets owned by the Tokyo Metropolitan Government and Shinjuku Ward. A total of 22 repeaters were installed in the Nishi-Shinjuku building area, and confirmed that the street coverage expanded from 33% to 99% compared to the existing millimeter-wave coverage.

・It was confirmed that the signals transmitted by these repeaters do not interfere with the signals transmitted from the same base station, allowing the millimeter-wave area to be expanded without the need for interference design.

２．Field Testing Period
From October 29, 2024, to March 31, 2025.

３．Field Testing Location
Nishi-Shinjuku district, Shinjuku Ward, Tokyo.

4．Roles of Each Company

KDDI	Developing millimeter-wave relay technology; planning/executing field testing.
Kyocera	Developing millimeter-wave repeaters.

５．Acknowledgement

Tokyo Metropolitan Government	Providing access to streetlights owned by Tokyo Metropolitan Government in Nishi-Shinjuku district.
Shinjuku Ward	Providing access to streetlights owned by Shinjuku Ward in the Nishi-Shinjuku district.

（1）World's first millimeter-wave relay technology that autonomously forms and reshapes coverage areas (as of December 16, 2024; according to KDDI's research).
（2）"Connected Tokyo" 3-year action plan (Tokyo Metropolitan Government) (in Japanese only)(PDF/3.56MB)

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