While most operators are focused, for now, on mid-band spectrum for 5G roll-out, a few want to start using millimeter wave bands above 20 GHz in the near term. One of these is SK Telecom, which is digging into the detail of how to make mmWave systems work effectively despite the spectrum’s short range.
Signals in the 28 GHz band, in which SK Telecom is testing 5G prototype equipment, travel over short distances and in straight lines. The company is focusing on relay technology, which is also being trialled by Softbank in Japan and others, to improve coverage and quality of service.
The operator has been working with its own integration subsidiary, SK Telesys, and with High Gain Antenna, to evaluate three design options for a 5G mmWave macrocell, which would get around the challenges of getting high frequency signals through walls and round obstacles.
It has decided that, of the options it studied, the most efficient is ‘multibeam generation and amplification’, which it has applied in its 5G trial network in the Gangnam district of capital Seoul. This achieved three times wider coverage than a single beam, said the operator – a single beam relay repeater covers 70 meters in the Gangnam environment, while the new repeater extended that to over 200 meters.