Method for transmit diversity of HARQ-ACK information feedback in a wireless communication system, said wireless communication system being adapted to employ transmit diversity and non-transmit diversity transmissions of HARQ-ACK information feedback, said method comprising: - receiving, by a user equipment, a first physical downlink control channel, PDCCH, and a second PDCCH on different component carriers; - implicitly determining resources for said HARQ-ACK information feedback from an enumeration describing which time-frequency resources each associated PDCCH is transmitted on, while the associated PDCCH does not carry explicit information of the resources for said HARQ-ACK information feedback; - assigning uplink control channel resources and modulation symbols to HARQ-ACK states for transmission of said HARQ-ACK information feedback over at least two antenna ports, wherein at least one of said uplink control channel resources is assigned to more than one of said at least two antenna ports, and wherein uplink control channel resources and modulation symbols assigned to HARQ-ACK states for one of said at least two antenna ports is the same as when non-transmit diversity of HARQ-ACK information feedback is employed, wherein the uplink control channel resources comprise reference signal sequences, data sequences, and QPSK symbols that modulate the data sequences; and - if the first PDCCH is missed while the second PDCCH is correctly received, feedbacking ACK or NACK for transport block/blocks associated with the second PDCCH by transmitting HARQ-ACK states in the form of ACK or NACK for one component carrier associated with the second PDCCH, and at the same time a feedback state discontinuous transmission, DTX, for another component carrier associated with the first PDCCH, on said at least two antenna ports. - receiving, by a user equipment, a first physical downlink control channel, PDCCH, and a second PDCCH on different component carriers; - implicitly determining resources for said HARQ-ACK information feedback from an enumeration describing which time-frequency resources each associated PDCCH is transmitted on, while the associated PDCCH does not carry explicit information of the resources for said HARQ-ACK information feedback; - assigning uplink control channel resources and modulation symbols to HARQ-ACK states for transmission of said HARQ-ACK information feedback over at least two antenna ports, wherein at least one of said uplink control channel resources is assigned to more than one of said at least two antenna ports, and wherein uplink control channel resources and modulation symbols assigned to HARQ-ACK states for one of said at least two antenna ports is the same as when non-transmit diversity of HARQ-ACK information feedback is employed, wherein the uplink control channel resources comprise reference signal sequences, data sequences, and QPSK symbols that modulate the data sequences; and - if the first PDCCH is missed while the second PDCCH is correctly received, feedbacking ACK or NACK for transport block/blocks associated with the second PDCCH by transmitting HARQ-ACK states in the form of ACK or NACK for one component carrier associated with the second PDCCH, and at the same time a feedback state discontinuous transmission, DTX, for another component carrier associated with the first PDCCH, on said at least two antenna ports.