Method and mobile node in a wireless communication network for determining when to transmit a signal. The mobile node operates in a wireless communication network comprising a first cell and a second cell where the mobile node is synchronized to the first cell. The method comprises determining a timing reference based on a reception of a downlink transmission in the first cell and transmitting the signal, to be received in the second cell, at a point in time based on the timing reference and a timing advance value of the first cell.