5G is approaching us with big steps, what means that companies working on the next generation of mobile networks are performing more and more interesting tests. So far, demonstration solutions have been based on the initial implementation of 5G technology, which offer high data rates but with a stationary terminal. On the other hand, NTT Docomo, Intel, Ericsson and Toyota have shown that 5G can also work in a driving car. Why is it so important?
The 5G NR standard that is still being developed assumes the use of OFDM modulation in the air interface. This technique involves simultaneous transmission of signals on orthogonal subcarriers. What does it mean? Their frequencies are so chosen that the signals do not interfere with each other. This is a very beautiful theory that is broken by the Doppler effect. What does the changing siren frequency and a wireless carriers have in common? The same thing happens with radio waves. In this case, the frequency of each subcarrier varies according to the speed at which the terminal is moving. Each of the subcarriers will change by the different frequency offset, what introduces interference between them. Therefore, for both 5G and LTE systems, it is important to implement the Doppler effect cancellation circuit.
In the latest 5G tests, 1 Gbps throughput was achieved for a vehicle traveling at 30 kph speed.
The recently announced speed records achieved with prototype 5G solutions may suggest that this is a poor result. But in the whole experiment, the most important thing is that the tests were conducted on the real streets of Tokyo, and the car was constantly connected to a 5G network consisting of 3 base stations. Therefore, continuous streaming of 4k video under such conditions should be impressive. The already mentioned 1 Gbps speed is the maximum value obtained during data receiving in a moving vehicle that has a suitable antenna installed on the roof. On the other hand, the data was sent from the car to base station at speeds of up to 600 Mbps.
Source: NTT Docomo