NTT DOCOMO, NEC Corporation, and NTT have jointly developed a new technology that enables stable, high-capacity millimeter-wave (mmWave) communications for vehicles traveling at high speeds. The technology, which leverages the 40 GHz band, is seen as a significant advancement toward the 6G era.
The technology combines distributed MIMO with a technique that pre-compensates the transmit frequency and timing of signals. A demonstration trial conducted in March 2026 at Japan's National Institute for Land and Infrastructure Management showed that multiple vehicles equipped with mobile terminals could maintain stable communication, achieving a 1.3x improvement in average throughput compared to conventional methods.
In high-frequency band communications like mmWave, high-mobility environments such as fast-moving automobiles and trains often suffer from frequent base station switching. This can lead to abrupt changes in Doppler frequency and propagation delay, degrading communication quality. DOCOMO, NEC, and NTT have been working to address these challenges, and in March 2025, they demonstrated a technology that stabilizes communication for a single high-speed vehicle.
The recent trial advanced this technology to suppress communication-quality degradation for multiple vehicles traveling at high speeds in opposite lanes. Using uplink reference signals from each vehicle, the technology pre-estimates the appropriate transmit frequency and timing for each base-station antenna, pre-compensates each vehicle-specific signal, and then multiplexes the signals for transmission. This process stabilizes high-capacity mmWave communications for multiple vehicles.
The trial involved two vehicles traveling at 60 km/h in opposite lanes within a tunnel, where radio waves reflect and antenna switching occurs frequently. The results showed that the proposed technology maintained stable throughput during antenna switching, improving average throughput to 560 Mbps, a 1.3x increase over the conventional method. Additionally, the 5th-percentile throughput value improved from 270 Mbps to 480 Mbps, an approximate 1.8x increase.
This development marks a major step toward the real-world deployment of 6G technologies. The successful demonstration paves the way for applications such as immersive in-vehicle XR, real-time translation, and sensor-data coordination for autonomous driving. DOCOMO, NEC, and NTT plan to conduct further trials in various real-world environments, including high-speed railways and arterial roads, to realize stable high-capacity communications in the 6G era.
The trial results will be exhibited at Wireless Japan × Wireless Technology Park 2026 and Tsukuba Forum 2026, showcasing the potential of mmWave communications in high-mobility environments.