A method of adjusting transmission power for data communicated in a mobile communication system, wherein data is transmitted from a source station to a destination station over a first route and a second route. The method comprises receiving a first transmission power control signal; wherein a destination station generates a second transmission power control signal, in response to receiving a quality measurement signal from the relay station for data communicated to the destination station over a combination of the first route and the second route; and adjusting data transmission power according to the first transmission power control signal.