NTT DOCOMO, Wednesday announced that in a joint trial of 5G technologies with Samsung, it has successfully achieved a data speed of more than 2.5Gbps with a mobile device that was in a vehicle travelling 150km/h. The trial verifies the feasibility of stable connectivity for 5G mobile devices in fast-moving trains.
The trial took place on November 7 in Fuji Speedway, a motorsport racing circuit in Shizuoka Prefecture, Japan.
Transmissions were conducted using the 28GHz high-frequency band, one of the candidate bands that the Ministry of Internal Affairs and Communications is considering to designate for commercial 5G networks in Japan.
NTT DOCOMO claims that to date, no test had achieved a successful wireless data transmission to a fast-moving device due to the large path-loss of high-frequency radio signals. In this trial, however, the problem was overcome with massive multiple-input multiple-output (MIMO) technologies that incorporate beamforming, which concentrates radio waves in a specific direction, and beam tracking, which adjusts the beam according to the fast-moving mobile device's location.
In a separate undertaking, DOCOMO conducted an outdoor data-transmission trial with Huawei from October 3 to 26. It was carried out in a field measuring 100,000 square meters, equivalent to 12 soccer pitches, in the Minato Mirai 21 waterfront of Yokohama. The trial involved 23 simultaneously connected mobile devices and achieved a cumulative 11.29Gbps of data throughput and latency below 0.5 seconds using the 4.5GHz frequency band.
The trial combined multi-user MIMO (MU-MIMO) technology for simultaneous multiple access and a precoding algorithm that optimizes signals for maximized performance and also limits inter-user interference. It achieved a MU-MIMO transmission of a maximum 79.82bps/Hz/cell, which was 1.8 times more efficient than an outdoor trial conducted in China in November 2015.
