The radio spectrum
Wireless communication is based on radio waves and bands of frequencies within the overall radio spectrum. We will cover long-range communication in the next chapter for cellular and other long-range mediums. Here we focus on the 1000-meter range or less. We will look at the spectrum allocation process as well as the typical frequency uses for WAN devices.
The spectrum ranges from 3 Hz to 3 THz, and allocation within the spectrum is governed by the International Telecommunication Union (ITU). A band is considered a portion of the spectrum that can be allocated, licensed, sold, or freely used depending on the frequency. From an ITU perspective, the bands are categorized as follows:
Figure 10: Frequency and band identification matrix for IEEE, EU, and ITU