Successful Demonstration of 5G (Millimeter Wave) Area Coverage Inside JR Yamanote Line Train Cars

KDDI and JR East have successfully demonstrated a system to provide 5G millimeter-wave coverage inside a Yamanote Line train. By receiving signals with a glass antenna on the window and re-radiating them inside, the area capable of 1Gbps speeds was improved from 40% to 97% of the car.
Technology DemonstrationNQ 96/100出典：PR Times

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  • 📰 Published: May 20, 2026 at 23:00
  • 🔍 Collected: May 20, 2026 at 14:31
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KDDI Corporation and East Japan Railway Company (JR East) announced the success of a demonstration to expand 5G (millimeter wave) area coverage inside a JR Yamanote Line train car. In this first-of-its-kind initiative in Japan, a glass antenna on the train's window received mmWave signals from a trackside base station, which were then amplified and re-radiated inside the car. This new configuration was confirmed to dramatically increase the area capable of 1Gbps communication speeds from approximately 40% to about 97% of the vehicle, overcoming the challenge of signal blockage by the train's metal body. The companies plan to leverage this technology to improve communication quality and convenience for passengers.

FAQ

What was the main achievement of this demonstration?

The successful creation of a stable, high-speed 5G millimeter-wave (mmWave) communication area inside a JR Yamanote Line train car, a challenging environment due to the signal-blocking metal structure.

How did the technology bring the 5G signal into the train?

It used a mmWave-compatible glass antenna on the train's window to receive the signal from a trackside base station. The signal was then amplified and re-radiated throughout the car using a dielectric waveguide and other antennas.

By how much did the 5G coverage inside the train improve?

The communication area capable of achieving speeds of 1Gbps was improved from approximately 40% of the vehicle to about 97%.

Which companies were involved in this project?

The demonstration was led by KDDI and JR East, with technological cooperation from AGC, Nippon Dengyo Kosaku, and Kyocera.

Why is it difficult to get a 5G mmWave signal inside a train?

5G mmWave signals have high directivity and are easily blocked by obstacles. The metal body of a train car acts as a shield, making it very difficult for the signal to penetrate from the outside.

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