A method of identifying interference in a cellular telecommunications network including a plurality of cells, each of which serves a plurality of mobile devices by radio link by using communication resources allocated to each of the mobile devices, the network having a frequency band allocated thereto, wherein the communication resources comprise respective frequency domain subcarriers, and the method including, for at least a particular cell of the plurality of cells: detecting radio quality within a number of subcarriers of the particular cell to produce measurement values; characterised in that: the radio quality comprises uplink received power, the uplink received power being detected for respective periods to produce ones of the measurement values for each of the subcarriers in each of the periods; and by the method further including: determining whether the subcarrier on which the uplink power is received is allocated to one of the plurality of mobile devices served by the particular cell; where it is determined that the subcarrier on which the uplink power is received is not allocated to one of the plurality of mobile devices served by the particular cell: comparing the received uplink power with a corresponding record of the measurement value for the subcarrier, and, dependent upon the comparison, updating the corresponding record of the measurement value for the subcarrier; and analysing selected ones of the record of measurement values to determine if the selected measurement values indicate the presence of interference, wherein the record of measurement values exclude a source of predictable interference due to not updating the measurement values relating to the subcarriers allocated to each of the mobile devices served by the particular cell during the period for which the measurement values were taken. detecting radio quality within a number of subcarriers of the particular cell to produce measurement values; characterised in that: the radio quality comprises uplink received power, the uplink received power being detected for respective periods to produce ones of the measurement values for each of the subcarriers in each of the periods; and by the method further including: determining whether the subcarrier on which the uplink power is received is allocated to one of the plurality of mobile devices served by the particular cell; where it is determined that the subcarrier on which the uplink power is received is not allocated to one of the plurality of mobile devices served by the particular cell: comparing the received uplink power with a corresponding record of the measurement value for the subcarrier, and, dependent upon the comparison, updating the corresponding record of the measurement value for the subcarrier; and analysing selected ones of the record of measurement values to determine if the selected measurement values indicate the presence of interference, wherein the record of measurement values exclude a source of predictable interference due to not updating the measurement values relating to the subcarriers allocated to each of the mobile devices served by the particular cell during the period for which the measurement values were taken. the radio quality comprises uplink received power, the uplink received power being detected for respective periods to produce ones of the measurement values for each of the subcarriers in each of the periods; and by the method further including: determining whether the subcarrier on which the uplink power is received is allocated to one of the plurality of mobile devices served by the particular cell; where it is determined that the subcarrier on which the uplink power is received is not allocated to one of the plurality of mobile devices served by the particular cell: comparing the received uplink power with a corresponding record of the measurement value for the subcarrier, and, dependent upon the comparison, updating the corresponding record of the measurement value for the subcarrier; and analysing selected ones of the record of measurement values to determine if the selected measurement values indicate the presence of interference, wherein the record of measurement values exclude a source of predictable interference due to not updating the measurement values relating to the subcarriers allocated to each of the mobile devices served by the particular cell during the period for which the measurement values were taken. determining whether the subcarrier on which the uplink power is received is allocated to one of the plurality of mobile devices served by the particular cell; where it is determined that the subcarrier on which the uplink power is received is not allocated to one of the plurality of mobile devices served by the particular cell: comparing the received uplink power with a corresponding record of the measurement value for the subcarrier, and, dependent upon the comparison, updating the corresponding record of the measurement value for the subcarrier; and comparing the received uplink power with a corresponding record of the measurement value for the subcarrier, and, dependent upon the comparison, updating the corresponding record of the measurement value for the subcarrier; and analysing selected ones of the record of measurement values to determine if the selected measurement values indicate the presence of interference, wherein the record of measurement values exclude a source of predictable interference due to not updating the measurement values relating to the subcarriers allocated to each of the mobile devices served by the particular cell during the period for which the measurement values were taken.