Absolute radio-frequency channel number

In GSM cellular networks, an absolute radio-frequency channel number (ARFCN) is a code that specifies a pair of physical radio carriers used for transmission and reception in a land mobile radio system, one for the uplink signal and one for the downlink signal. ARFCNs are for GSM defined in Specification 45.005 Section 2. There are also other variants of the ARFCN numbering scheme that are in use for other systems that are not GSM. One such example is the TETRA system that have 25 kHz channel spacing and use different base frequencies for numbering.