(b) RF conversion
In the context of cognitive radios, RF conversion is a function of the radio model. It involves converting signals between different frequency bands, which is crucial for enabling dynamic spectrum access. RF conversion typically includes processes like upconversion and downconversion of radio frequencies to ensure that the cognitive radio can operate across different spectrum bands.
DSP (Digital Signal Processing) and coding are related to signal processing tasks but are not specifically part of the radio model itself. The user interface is also not part of the radio model but is related to the overall system's interaction with the user.