A radio receiver is provided for low-power detection of a radio signal, wherein said receiver is configured to receive a radio signal over a radio network; convert at least part of the received radio signal into a sequence of samples; compare the similarity of a first part of the sequence and a second part of the sequence, wherein the first part and the second part are of equal length; and in response to said similarity being greater than a similarity threshold: detect a phase difference between the first part of the sequence and the second part of the sequence; calculate a frequency offset between a frequency of the received radio signal and an expected frequency of the received radio signal using said phase difference; and use said calculated frequency offset to attempt full access to the radio network.