The radio spectrum is the part of the electromagnetic spectrum with frequencies from 30 Hertz to 300 GHz
ITU (International Telecommunications Union) is the United Nations specialized agency for information and communication technologies(ICTs). Radio Bands (Spectrum Band) are designated by the ITU Radio Regulations.ITU allocates global radio spectrum and satellite orbits.
802.11 is a standard that was developed by the Institute of Electrical and Electronic Engineers (IEEE).
It is the original wireless specification. This first IEEE standard for Wi-Fi was released in 1997 and is known as IEEE 802.11. It had major shortcomings of a maximum speed of 2 Mbps Later on various Extensions of the 802.11 were released.
The radio spectrum frequency bands used by the International Telecommunications Union (ITU) ie the variants of 802.11x and are 802.11a,802.11b,802.11d—–802.11k,802.11n, which are either upgrades over the previous spectrum or independently adds more capabilities. So there are different flavors of 802.11 with different functionalities. The important Protocols are
Protocol Frequency Max data rate (Mbps)
802.11b 2.4GHz 11
802.11g 2.4 GHz 54
802.11a 5GHz 54
802.11n 2.4GHz 217
802.11n 5GHz 450
802.11ac 5GHz 433
A compatible device to receive Wi-Fi can have multiple protocols such as 802.11a/g/as