A frequency estimation circuit for a reference-less repeater circuit comprises an edge detector configured to measure time periods between edge-to-edge transitions in a data stream within a predetermined time interval, resulting in a plurality of edge-to-edge time periods; and a processor configured to categorize the plurality of edge-to-edge time periods into a plurality of representative groups, each representative group having a representative time period that is an integer multiple of a sampling unit time period; to determine a number of virtual transitions in the predetermined time interval based on the categorized plurality of edge-to-edge time periods and to determine a frequency estimate of the data stream based on the number of virtual transitions in the predetermined time interval.