A recipient, for providing hybrid automatic repeat request, HARQ, feedback for data received in a downlink using carrier aggregation of a downlink Frequency-Division Duplexing, FDD, carrier and at least one Time-Division Duplexing, TDD, carrier, in an uplink control channel resource in an uplink FDD carrier, said recipient comprising: a memory storing program instructions; and a processor coupled to the memory; wherein when executed by the processor, the instructions cause the recipient to: receive data carried in one or both of: a subframe on a downlink data channel of a FDD carrier, and a downlink subframe on a downlink data channel of a TDD carrier; determine whether the data has been correctly received; select a sequence and a modulation symbol, or select a modulation symbol, to form a HARQ feedback indicating whether the data has been correctly received; and transmit the HARQ feedback in an uplink control channel subframe of an uplink FDD carrier, wherein spatial bundling is performed in the uplink control channel subframe if the uplink control channel subframe is assigned for HARQ feedback of both the downlink FDD carrier and the TDD carrier; and spatial bundling is not performed in the uplink control channel subframe if the uplink control channel subframe is assigned for HARQ feedback of only the downlink FDD carrier. a memory storing program instructions; and a processor coupled to the memory; wherein when executed by the processor, the instructions cause the recipient to: receive data carried in one or both of: a subframe on a downlink data channel of a FDD carrier, and a downlink subframe on a downlink data channel of a TDD carrier; determine whether the data has been correctly received; select a sequence and a modulation symbol, or select a modulation symbol, to form a HARQ feedback indicating whether the data has been correctly received; and transmit the HARQ feedback in an uplink control channel subframe of an uplink FDD carrier, wherein spatial bundling is performed in the uplink control channel subframe if the uplink control channel subframe is assigned for HARQ feedback of both the downlink FDD carrier and the TDD carrier; and spatial bundling is not performed in the uplink control channel subframe if the uplink control channel subframe is assigned for HARQ feedback of only the downlink FDD carrier. receive data carried in one or both of: a subframe on a downlink data channel of a FDD carrier, and a downlink subframe on a downlink data channel of a TDD carrier; a subframe on a downlink data channel of a FDD carrier, and a downlink subframe on a downlink data channel of a TDD carrier; determine whether the data has been correctly received; select a sequence and a modulation symbol, or select a modulation symbol, to form a HARQ feedback indicating whether the data has been correctly received; and transmit the HARQ feedback in an uplink control channel subframe of an uplink FDD carrier, wherein spatial bundling is performed in the uplink control channel subframe if the uplink control channel subframe is assigned for HARQ feedback of both the downlink FDD carrier and the TDD carrier; and spatial bundling is not performed in the uplink control channel subframe if the uplink control channel subframe is assigned for HARQ feedback of only the downlink FDD carrier.