The invention relates to a method and an arrangement for obtaining efficient radio resource allocation in a mobile communication network comprising a communication network entity (15) and at least one user equipment (18) transmitting data to said mobile communication network entity (15) over a radio interface. A first data transmission from said at least one user equipment (18) is received, whereby said first transmission is decoded and a message (ACK/NACK) based on a result of the decoding is sent on a downlink channel (13) comprising information of said first received data transmission. A second data transmission from said at least one user equipment (18) is received, whereby the power on said downlink channel (13) is adjusted depending on the result of said decoding and the content in said received second data transmission.