Radio spectrum is the range of electromagnetic frequencies used to transmit information without wires. Mobile networks use particular bands within that range, but broadcasters, satellites, aviation systems, emergency services and Wi-Fi also rely on spectrum.
A mobile operator often needs a government license for a particular band in a particular area. Not all spectrum is licensed in the same way: some bands allow unlicensed operation under technical rules, and some services share access. Regulators set conditions to reduce harmful interference between users.
Lower frequencies can often cover larger areas and penetrate buildings more easily, while higher frequencies can provide wider channels for capacity but may need denser infrastructure. Existing spectrum assignments can make a new generation difficult to roll out, even when the new radios are technically ready.
When comparing 5G and 6G plans, look for the actual frequency band, bandwidth, national allocation, license status and compatibility with existing users. A promising frequency range in a research paper is not automatically available for commercial networks.