Smartphones today support a variety of cellular protocols including GSM, 3G, 4G, and LTE. These protocols are complicated and require a large amount of CPU power to process data, generate packets, and transmit them to the network provider. To handle this process, smartphones now use a baseband modem, which is a separate chip included in smartphones that communicates with the main processor. These baseband modems have their own processor called the baseband processor and run their own operating system. The baseband processor manages several radio control functions such as signal generation, modulation, encoding, as well as frequency shifting. It can also manage the transmission of signals.

The baseband processor is generally located on the same circuit board as the CPU, but consists of a separate radio component.