A method in a radio network node, for data transmission and assignment of uplink control channel resources in an uplink Frequency-Division Duplexing, FDD, carrier, for enabling a recipient to provide Hybrid Automatic Repeat request, HARQ, feedback for data transmitted in a downlink using carrier aggregation of a downlink FDD carrier and at least one Time-Division Duplexing, TDD, carrier, wherein the method comprises: associating each downlink subframe in the downlink FDD carrier with an uplink control channel subframe in the uplink FDD carrier; associating each downlink subframe and special subframe in the TDD carrier with an uplink control channel subframe in the uplink FDD carrier; assigning uplink control channel resources in the uplink control channel subframe in the uplink FDD carrier to the recipient, according to the said associations (501, 502); and transmitting data on at least one of said downlink FDD carrier and TDD carrier, to be received by the recipient; wherein the association of each downlink subframe in the downlink FDD carrier and the association of each downlink subframe and special subframe in the TDD carrier with an uplink control channel subframe in the uplink FDD carrier generates at least one uplink control channel subframe in the uplink FDD carrier comprising only HARQ feedback related to the downlink FDD carrier; the method further comprises receiving HARQ feedback from the recipient, related to the transmitted data, on the uplink control channel resource in the uplink control channel subframe in the uplink FDD carrier assigned to the recipient; wherein the HARQ feedback is received on a scheduling request resource; and wherein spatial bundling is performed in uplink control channel subframes which are assigned for HARQ feedback of both the downlink FDD carrier and TDD carrier (200, 250); and spatial bundling is not performed in uplink control channel subframes which are assigned for HARQ feedback of the downlink FDD carrier. associating each downlink subframe in the downlink FDD carrier with an uplink control channel subframe in the uplink FDD carrier; associating each downlink subframe and special subframe in the TDD carrier with an uplink control channel subframe in the uplink FDD carrier; assigning uplink control channel resources in the uplink control channel subframe in the uplink FDD carrier to the recipient, according to the said associations (501, 502); and transmitting data on at least one of said downlink FDD carrier and TDD carrier, to be received by the recipient; wherein the association of each downlink subframe in the downlink FDD carrier and the association of each downlink subframe and special subframe in the TDD carrier with an uplink control channel subframe in the uplink FDD carrier generates at least one uplink control channel subframe in the uplink FDD carrier comprising only HARQ feedback related to the downlink FDD carrier; the method further comprises receiving HARQ feedback from the recipient, related to the transmitted data, on the uplink control channel resource in the uplink control channel subframe in the uplink FDD carrier assigned to the recipient; wherein the HARQ feedback is received on a scheduling request resource; and wherein spatial bundling is performed in uplink control channel subframes which are assigned for HARQ feedback of both the downlink FDD carrier and TDD carrier (200, 250); and spatial bundling is not performed in uplink control channel subframes which are assigned for HARQ feedback of the downlink FDD carrier.