On May 25, NTT DoCoMo and NEC announced the joint development of technology using high-capacity millimeter wave (40GHz band) communications with NTT. When communicating in high frequency bands such as millimeter waves while moving at high speeds, such as in cars or trains, there is a problem in that the Doppler frequency and propagation delay of the radio waves change rapidly due to the frequent switching of base stations, resulting in a decline in communication quality. This time, by developing the technology that was successfully demonstrated in March 2025, the company succeeded in suppressing the deterioration of the communication quality of each wireless terminal vehicle, even under complex conditions where multiple wireless terminal vehicles traveling at high speeds facing each other in oncoming lanes communicate simultaneously. Specifically, the uplink reference signal sent from each wireless terminal vehicle to each base station antenna is used to pre-estimate the appropriate transmission frequency and signal transmission timing for each wireless terminal vehicle. By pre-correcting the signals to be multiplexed for each wireless terminal vehicle, combining them, and transmitting them, differences in reception frequency and reception timing when switching antennas in multiple wireless terminal vehicles are simultaneously eliminated. The demonstration experiment was conducted from March 26th to 27th at the full-scale tunnel experimental facility within the National Institute for Land and Infrastructure Management, Ministry of Land, Infrastructure, Transport and Tourism. To simulate a high-speed moving environment, three base station distributed antennas were installed at 150m intervals on one side of the road, and two wireless terminal vehicles were driven in opposite lanes at 60km/h to conduct a downlink transmission experiment. In the case of the conventional technology, the total throughput when switching antennas decreased from 550 Mbps to about 110 Mbps, and the average throughput during 30 seconds of running was about 430 Mbps. This technology maintains a stable high throughput of over 380Mbps, and the average throughput is 560Mbps, approximately 1.3 times better than conventional technology. The throughput of the bottom 5% of the Cumulative Distribution Function (CDF) was also confirmed to be 480Mbps, an improvement of about 1.8 times compared to the 270Mbps of the conventional technology. The success of this demonstration is expected to lead to the use of millimeter wave communications for immersive services such as in-vehicle XR (augmented reality), real-time translation/guidance using generative AI, and sensor data linkage for cooperative autonomous driving. In the future, the company plans to conduct demonstration experiments in various real-world environments, such as high-speed railways, conventional lines, and highways. The details and results of this demonstration will be exhibited at ``Wireless Japan x Wireless Technology Park (WTP)'' and ``Tsukuba Forum 2026.''
