A fundamental aspect of 5G is New Radio (NR). This new radio access technology uses in the following three broad spectrum frequency bands.
Millimetre wave or mmWave (26GHz and above). This band provides the best performance but is limited by short distances that require many cell sites to provide coverage. mmWave was seen as the focus for 5G initially, but deployment costs and the inability of mmWave signals to penetrate walls have limited the use of this band to a few urban market deployments.
C-band (2–6GHz). This is sometimes called mid-band, and is now the ‘sweet spot’ for 5G deployments. Recent auctions in the USA produced bids of over USD80 billion. C-band spectrum covers about 1km from a tower and offers good in-building penetration but with less capacity than mmWave. Most countries have focused on C-band spectrum for 5G. Strictly speaking, C-band is 3.4–4.2GHz, but some operators are using nearby spectrum that was allocated previously – for example, T-Mobile USA is using spectrum in the 2.5GHz band.
Sub-1GHz. 5G NR can operate in the 600MHz or 700MHz bands. Operators use sub-1GHz to get wide coverage – over 100km – but this offers no better throughput than LTE.
5G NR requires massive multi-input multi-output (MIMO) antennas, particularly for C-band deployments. This technology increases the data capacity of the cell sites where it is deployed. MIMO technology allows transmission of more than one data signal over the same channel. It is widely used in 4G and Wi-Fi, and typically involves two or four antennas. Massive MIMO usually involves more than 100 radios but it can be fewer.
Massive MIMO inherently includes beamforming to improve signal quality, extending the effective reach of coverage from a cell site.