The invention relates to methods for reporting on downlink timings by a mobile terminal in a mobile communication system. In order to allow for an aggregation access point to obtain information on propagation delay differences of downlink transmissions on aggregated serving cells, the invention suggests the mobile terminal to report timing information based on reception time difference information for a the target/reference cell. The mobile terminal performs measurements relating to transmission and/or reception time differences on the target/reference cell, and reports same to the eNodeB. The eNodeB compares the measurement result to a predefined maximum propagation delay time difference. Alternatively, the mobile terminal performs the measurements, compares same to the predefined maximum propagation delay time difference and then report the comparison result to the eNodeB.