Most of the 5G tests are conducted in stationary conditions or using slow moving cars. In contrast, the Japanese operator NTT DoCoMo and NEC tested the behaviour of the new technology on the racetrack. The car moving at 300 kph was equipped with 5G equipment using the 28 GHz band. The peak data transmission speed was 1.1 Gbps.
What problems did the engineers working on this project have to solve? First, the car was passing by two base stations and switching between them. Thus, a small 5G network had to perform the so-called a handover that ensures continuous data transmission when switching between network cells. If this process did not take place within the prescribed time, the connection would be restarted and the speed of data transmission would be reduced. Another problem was to take into account the Doppler effect. This phenomenon consists in changing the frequency of the radio signal when one of the antennas moves relative to the other. This change is all the greater, the higher the signal frequency and the transmitter’s speed. At 28 GHz and a speed of 300 kph, this change is only 7.8 kHz, but this is enough to increase the interference between the sub-carriers of the transmitted signal.
During the test, also 4K image streaming at the speed of 200 kph was successful
The last aspect of the demonstrated experiment is to test the smooth operation of the algorithms that followed the location of the car and real-time modelled the radio channel. 5G networks operating in the millimetre range will be equipped with special antennas that will only send the signal in the direction of the selected user. If its location changes, then the antenna must change the angle at which it radiates the electromagnetic wave. With a car speeding at 300 kph, the system must adapt to changes immediately.
The intended data download speed, i.e. 1.1 Gbps in the 700 MHz channel, was achieved at a speed of 300 kph. However, in the test of sending data, it was necessary to slow down. The Japanese operator did not show any concrete values here. It is only known that during the transit an uncompressed image with 4K resolution was sent in 120 frames per second. Streaming in real time was possible at a speed of 200 kph. Who knows, maybe in a few years we will be watching car racing from the perspective of the driver.