Talk about mobility. Japan’s NTT DoCoMo says it just completed a 5G trial with Samsung Electronics that achieved a data speed of more than 2.5 Gbps with a mobile device that was in a vehicle traveling 150 km/h (about 93 mph), thereby showing the feasibility of connectivity for 5G devices in fast-moving trains.
The trial took place on Nov. 7 in Fuji Speedway, a motor-racing circuit in Shizuoka Prefecture, Japan. Transmissions were conducted using the 28-GHz band, a popular band for 5G tests in the U.S. and one of the candidate bands that Japan’s Ministry of Internal Affairs and Communications is considering to designate for commercial 5G networks in Japan.
According to DoCoMo’s press release, no test to date 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.
Much of the early 5G work in the U.S. revolves around fixed wireless rather than mobility. Earlier this year, Verizon CFO Fran Shammo reiterated the company's commitment to be the first in the U.S. to roll out 5G wireless technology and made it clear that its initial pilot starting in 2017 is all about fixed wireless, not mobility. AT&T executives have also said they think 5G will be about fixed wireless with limited mobility in the near term.
In a separate undertaking, DoCoMo conducted an outdoor data-transmission trial with Huawei from Oct. 3 to Oct. 26 in a field measuring 100,000 square meters—equivalent to 12 soccer fields—in the Minato Mirai 21 waterfront of Yokohama. The trial involved 23 simultaneously connected mobile devices and achieved a cumulative 11.29 Gbps of data throughput and latency below 0.5 seconds using the 4.5-GHz frequency band.
The trial combined multiuser MIMO (MU-MIMO) technology for simultaneous multiple access and a precoding algorithm that optimizes signals for maximized performance and limits inter-user interference. It achieved a MU-MIMO transmission of a maximum 79.82 bps/Hz/cell, which was 1.8 times more efficient than an outdoor trial conducted in China in Nov. 2015, the operator said.
That’s not all, however. Separately, Huawei, which began 5G research in 2009, and Australian operator Optus announced that they successfully completed a 5G network trial that achieved the fastest speeds observed of a single-user transmission over 5G in Australia thus far. That trial took place in Sydney and reached a single-user transmission rate of 35 Gbps over the 73-GHz band.
The objective of the trial was to explore spectrum efficiency at millimeter-wave frequencies above 30 GHz and used technologies such as Polar code, a coding mechanism used to demonstrate 5G.