The 5G NG (New Radio) operates in the wireless band between 28GHz to 60GHz, also the sub 6GHz unlicensed radio frequency will be used. With a much broader range of radio frequency used and in consolidation, we usually refer to it as millimetre wave or mm-Wave for short.
The small cell infrastructure will be essential to the 5G networks, as the implementation will reduce cost by reducing the number of rooftop outdoor cellular base-stations. Lesser power consumption at both the base station and also on the mobile devices because of the shorter transmission range for 5G networks.