ARFCN is an Absolute Radio-Frequency channel Number is a unique number that is given to each radio channel in GSM technology. The ARFCN can be used to calculate the exact frequency of the radio channel. Within the GSM 900 band, ARFCN 1 to 124 is used. In the GSM 1800 band, ARFCN 512 to 885 are used. The ARFCNs used in GSM 1900 band overlap with the ARFCNs used in the 1800 band.