A base station comprising: a downlink transmission power decider configured to decide, according to received qualities at user devices, different downlink transmission powers for transmitting downlink data to the user devices UEs; and a radio transmitter configured to transmit a mixed data signal in which data signals that are not orthogonal to each other are mixed, each of the data signals being addressed to a corresponding one of the user devices UEs, such that each data signal is transmitted with a corresponding one of the downlink transmission powers decided by the downlink transmission power decider, and to transmit control signals to the user devices UEs to enable each user device to decode the data signal addressed to the user device using a control signal, among the control signals, corresponding to the user device, wherein the radio transmitter is configured to transmit each control signal in a format in which the control signal is scrambled by an identifier of the user device corresponding to the control signal, wherein the radio transmitter, at a cycle longer than a transmission cycle of the control signals, is configured to notify the user devices UEs of a list in which identifiers of the user devices UEs, to which the data signals that are not orthogonal to each other are addressed, are associated in a one-to-one correspondence with indices that each have a shorter length than the identifiers, and wherein in order to enable a first user device, to which a first data signal is addressed, to descramble a control signal for at least one second user device, to which at least one second data signal is addressed, the radio transmitter is configured to include, in a control signal for the first user device, an index that corresponds to the at least one second user device, the first user device and the at least one second user device being among the user devices (UEs), the first data signal having a downlink transmission power that is not the highest among the downlink transmission powers decided by the downlink transmission power decider, the second data signal being mixed in the mixed data signal together with the first data signal. a downlink transmission power decider configured to decide, according to received qualities at user devices, different downlink transmission powers for transmitting downlink data to the user devices UEs; and a radio transmitter configured to transmit a mixed data signal in which data signals that are not orthogonal to each other are mixed, each of the data signals being addressed to a corresponding one of the user devices UEs, such that each data signal is transmitted with a corresponding one of the downlink transmission powers decided by the downlink transmission power decider, and to transmit control signals to the user devices UEs to enable each user device to decode the data signal addressed to the user device using a control signal, among the control signals, corresponding to the user device, wherein the radio transmitter is configured to transmit each control signal in a format in which the control signal is scrambled by an identifier of the user device corresponding to the control signal, wherein the radio transmitter, at a cycle longer than a transmission cycle of the control signals, is configured to notify the user devices UEs of a list in which identifiers of the user devices UEs, to which the data signals that are not orthogonal to each other are addressed, are associated in a one-to-one correspondence with indices that each have a shorter length than the identifiers, and wherein in order to enable a first user device, to which a first data signal is addressed, to descramble a control signal for at least one second user device, to which at least one second data signal is addressed, the radio transmitter is configured to include, in a control signal for the first user device, an index that corresponds to the at least one second user device, the first user device and the at least one second user device being among the user devices (UEs), the first data signal having a downlink transmission power that is not the highest among the downlink transmission powers decided by the downlink transmission power decider, the second data signal being mixed in the mixed data signal together with the first data signal.