SK Telecom and Nokia Networks have presented the use of super high frequency (ang. CmWave) representing another step towards the standardization of the 5G technology. In joint trials in South Korea, the two companies reached the speed of 19.1 Gbps of wireless data transmission.
This level of performance was made possible by using 256QAM modulation, MIMO in 8×8 configuration, and the frequency band width of 400MHz.
The speed of 19.1 Gbps means downloading approx. 2.4 GB per second (at the application level this value will be a lower). 9 GB full HD movie can be downloaded at this speed in 4 seconds. 144 GB of data can be uploaded in one minute, and 720 GB in five minutes. This result is certainly impressive. However, it is worth remembering that the indicated speed is the maximum that a single user could get. With the increase in number of active users, this result will be shared between them.
It was not specified what frequency was used for testing, but it was somewhere in the range of cm-Wave, which ranges, by definition from 3 to 30 GHz (1 to 10 cm wavelength). The main difference compared to the currently used bands to provide telecommunications services is greater signal attenuation with increasing frequency and distance from the transmitter. Not by chance during the last LTE auction in Poland, even 40 times higher amounts have been achieved for the same bandwidth (5 MHz) at lower frequency of 800 MHz than on the higher frequency of 2600 MHz.
The table below presents a simplified comparison of the effect of frequency on the range (distance and coverage around the transmitter) at a constant level of the signal being received. The power radiated by the transmitter was assumed to be at 24 dBm and the average signal level of -90 dBm which is to be received, for example, by a phone (114 dB signal attenuation on the path from the transmitter to the receiver).
- Frequencies from the last LTE auction:
- 800 MHz – 14.5 km (660 km2)
- 2600 MHz – 4.6 km (66 km2)
- • Limiting frequencies of cm-Wave:
- 3 GHz – 4 km (50 km2)
- 30 GHz – 0.4 km (0.5 km2).
The above comparison shows that the difference in coverage between the LTE frequencies auctioned currently in Poland is significant. At a given level of signal it amounts to as much as 10 km. Less spectacular differences are seen among limiting frequencies of cm-Wave. The coverage itself reaches only 0.4 km in open space, so taking into account the attenuation of walls, indoor coverage will be even smaller.
In summary, the use of higher frequencies is associated with access to a wider frequency bands that will allow achieving higher mobile Internet bandwidths. The range currently used is very crowded by various radio transmissions which prevent separation of the broad frequency bands for telecommunications services. However, the higher frequency range requires the compaction of the quantity of transmitters to provide coverage to users. From the user’s perspective, it has its positive consequences – reducing the number of users connected to a single base station, or in other words an increase in average bitrate per one user. However, for mobile operators it can lead to larger financial outlays, not only for the purchase of more base stations but also for the lease of land in new locations.