Press Releases

May 27, 2026

KDDI and NTT DOCOMO Develop Shared Repeater to Efficiently Expand Millimeter-Wave Coverage
—Field Test to Begin This Summer at Tokyo's Ueno Park, Accelerating Millimeter-Wave Deployment Through Operator Collaboration—

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KDDI Corporation
NTT DOCOMO, INC.

TOKYO, JAPAN, May 27, 2026 --- KDDI Corporation (KDDI) and NTT DOCOMO, INC. (DOCOMO) today announced the successful development of a shared repeater for millimeter-wave signals.^*1 Developed in cooperation with Kyocera Corporation (Kyocera), this shared repeater is designed to efficiently expand millimeter-wave service coverage. The two operators will begin field-testing using the repeater in Ueno Park, Tokyo, this summer.

This shared repeater can simultaneously relay millimeter-wave signals from both KDDI and DOCOMO base stations, enabling more efficient expansion of millimeter-wave coverage. Moving forward, the two operators will evaluate the repeater's effectiveness and continue collaborating to expand their millimeter-wave networks.

Background
5G communication leverages the wide bandwidth of the millimeter-wave spectrum to deliver ultra-high-speed, high-capacity data transmission. However, millimeter-wave signals travel in straight lines and are easily obstructed by physical barriers, which has traditionally required the installation of numerous base stations to create continuous coverage.

To overcome this challenge, KDDI developed a wireless relay technology in December 2024 that enables autonomous and continuous area formation by relaying signals from millimeter-wave base stations.^*2 KDDI has since been expanding its millimeter-wave coverage using repeaters equipped with this technology, focusing on high-traffic areas in Tokyo such as the Nishi-Shinjuku district and the area around Takanawa Gateway station. Concurrently, DOCOMO has been expanding its millimeter-wave coverage in entertainment venues, including stadiums.

This new shared repeater was developed to further accelerate the expansion of millimeter-wave coverage, which until now has been pursued independently by each operator.

The Shared Repeater

1. Multi-Operator Compatibility
   Manufactured by Kyocera, this repeater supports millimeter-wave signals from both KDDI and DOCOMO within a single unit—a significant upgrade from conventional repeaters that could only relay signals for a single operator. This innovation enables both operators to efficiently provide and expand stable millimeter-wave services for their respective customers.

   This breakthrough was achieved by integrating filters and amplifier circuits, which previously required separate implementation for each operator, into a shared configuration within the existing device housing. The repeater is equipped with a function to detect incoming signals from each operator and select the optimal antenna face. This mitigates variations in communication quality caused by differences in the direction and strength of incoming signals. By deploying these shared repeaters, operators can significantly reduce installation costs and physical space requirements compared to installing separate units.

2. Key Features

   1. 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.

      

   2. Optimizing Relay Routes
      The 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 detect 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.

      

   3. Compact and Lightweight
      The 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.

Upcoming Field Test

The field test will be conducted in Tokyo's Ueno Park, a location that attracts a large number of visitors and requires robust, high-quality network capacity. By installing the shared repeaters in the park to relay signals from KDDI and DOCOMO millimeter-wave base stations, the operators will expand their respective millimeter-wave service areas. This test will evaluate the following points to assess the repeater's viability for future commercial deployment:

• Area expansion effectiveness (coverage, communication quality, data speeds, etc.)
• Performance of autonomous area formation and route optimization in response to environmental changes
• Operational benefits, including reduced equipment costs and improved installation efficiency

1. 28GHz frequency band
2. KDDI News Release, December 16, 2024: “KDDI and Kyocera Succeed in Developing Wireless Relay Technology That Dramatically Expands Millimeter-Wave Coverage”