5G refers to the fifth generation of mobile communication sys­tems. The formal criteria for mobile communication systems, in order to be called “5G”, are set by ITU (International Telecom­munications Union) and documented in IMT-2020 (Interna­tional Mobile Telecommunications) requirement set.

Band is a generic term for the proportion of radio frequency. Each 5G operator has one or more frequency bands which are used for radio transmission and reception. Operators typi­cally purchase the right to use frequency bands for their opera­tions from auctions organized by national regulators. In 5G, the low-band refers to spectrum below 1 GHz, mid-band to 1-6 GHz, and high-band to spectrum range above 6 GHz.

Base Station refers to a physical site where radio and transmis­sion equipment are located for interconnecting user equipment (UE) and cellular network. In 5G, the radio component is called gNB (next genera­tion Node B). In LTE, it is eNB (evolved Node B), and in 3G it is NB (Node B).

CA (Carrier Aggregation) refers to the combining of radio ca­pacity of two or more radio frequency bands for a single user. CA has been applied since 2G, but 5G is able to benefit even more from it, thanks to the wider defined bandwidths.

Core Network connects the 5G base stations and delivers the data traffic and signaling between the user equipment and des­tination such as other mobile user equipment or server. In 5G, the core network is based on virtualized architecture, clouds, and data centers.