For example, in analog radio broadcasting (AM and FM), there are a limited number of channels allocated by government regulations. In the United States, there are approximately 10,000 AM and 15,000 FM radio stations, each operating on its own assigned frequency. These frequencies are divided into various bands, such as the AM broadcast band (535-1705 kHz) and the FM broadcast band (88-108 MHz).
In digital radio broadcasting (such as DAB+), the concept of channels is different. DAB+ uses multiplexing technology that allows multiple digital audio streams to be transmitted on a single frequency channel. This allows for a greater number of channels in the same allocated spectrum. In addition to traditional radio channels, there are also channels dedicated to specialized services such as marine radio, aviation radio, emergency communications, and mobile radio (cellular networks).
In mobile communication systems (cellular networks), the concept of channels is related to the frequency bands allocated for wireless services. These frequency bands are divided into multiple channels, each with a specific bandwidth and carrier frequency. The number of channels available depends on the specific cellular technology and spectrum allocation in each country or region.
For instance, in GSM, each carrier frequency is divided into 124 channels, each with a bandwidth of 200 kHz. In LTE (Long-Term Evolution), the channels are called resource blocks, and they can vary in size and be aggregated to achieve higher data rates.