A mobile device in a communication system that executes transmitting and/or receiving during fixed transmission time intervals, TTIs, configured to: receive downlink data transmitted from a base station and indicate whether or not the receipt of the downlink data has succeeded to the base station, wherein the mobile device is further configured to: in case of an unsuccessful receipt of the downlink data, activate reception for a first retransmission of the downlink data which is retransmitted from the base station after a first number of TTIs pass from a TTI in which the downlink data has been received, in case of an unsuccessful receipt of the first retransmission of the downlink data, activate reception for a second retransmission of the downlink data which is retransmitted from the base station after a round-trip time, RTT, passes from a TTI in which the first retransmission of the downlink data is received, and maintain the reception for the second retransmission of the downlink data activated until receipt of the second retransmission; activate reception for an ACK signal or a NACK signal in a TTI in which reception for a retransmission of the downlink data is activated; wherein said a first number of TTIs is equal to one RTT. receive downlink data transmitted from a base station and indicate whether or not the receipt of the downlink data has succeeded to the base station, wherein the mobile device is further configured to: in case of an unsuccessful receipt of the downlink data, activate reception for a first retransmission of the downlink data which is retransmitted from the base station after a first number of TTIs pass from a TTI in which the downlink data has been received, in case of an unsuccessful receipt of the first retransmission of the downlink data, activate reception for a second retransmission of the downlink data which is retransmitted from the base station after a round-trip time, RTT, passes from a TTI in which the first retransmission of the downlink data is received, and maintain the reception for the second retransmission of the downlink data activated until receipt of the second retransmission; activate reception for an ACK signal or a NACK signal in a TTI in which reception for a retransmission of the downlink data is activated; wherein said a first number of TTIs is equal to one RTT. in case of an unsuccessful receipt of the downlink data, activate reception for a first retransmission of the downlink data which is retransmitted from the base station after a first number of TTIs pass from a TTI in which the downlink data has been received, in case of an unsuccessful receipt of the first retransmission of the downlink data, activate reception for a second retransmission of the downlink data which is retransmitted from the base station after a round-trip time, RTT, passes from a TTI in which the first retransmission of the downlink data is received, and maintain the reception for the second retransmission of the downlink data activated until receipt of the second retransmission; activate reception for an ACK signal or a NACK signal in a TTI in which reception for a retransmission of the downlink data is activated; wherein said a first number of TTIs is equal to one RTT. <EOS>