In a mobile network, the transmission of downlink data blocks (303, 307) to one or more terminal devices (200, 210) is accomplished on the basis of a retransmission protocol with a first feedback time (F1) defining a time interval between transmission of a first data block (303) and transmission of a first feedback message (308) being different from a second feedback time (F2) defining a time interval between transmission of a second data block (307) and transmission of a second feedback message (309). The first feedback message (308) indicates whether the first data block (303) was successfully received, and the second feedback message (309) indicates whether the second data block (307) was successfully received. A base station (100) of the mobile network controls the terminal device (200, 210) to send the second feedback message (309) on other resources than used for transmission of the first feedback message (308).