A method for identifying supported transmission channel configurations in a mobile communications apparatus, the method comprising: calculating the required power value for each transmission channel configuration; and performing a sequential comparison of: an indication of an available measured power value, and an indication of the required power for each transmission channel configuration; and identifying a particular transmission channel configuration as supported if the required power for the particular transmission channel configuration is less than the available power value; wherein: the sequential comparison is performed in order of magnitude of value of the indication of the required power; and the method further comprising stopping said comparison when a supported transmission channel configuration is identified.