A method of wireless communication for a system that supports a set of component carriers in carrier aggregation, wherein the set of component carriers comprise a frequency-division duplexing, FDD, primary component carrier, PCC, and a time-division duplexing, TDD, secondary component carrier, SCC, the method comprising, at a user equipment: determining a downlink/uplink, DL/UL, configuration for the TDD-SCC; identifying a scheduling timing between a first uplink grant and a corresponding uplink transmission for the TDD SCC based on a scheduling time of the FDD PCC; determining an uplink hybrid automatic repeat request, HARQ, timing of the TDD SCC based at least in part on a frame period of the TDD SCC, wherein a number of subframes in the frame period of the TDD SCC is determined by the DL/UL configuration for the TDD-SCC, and wherein the determining the HARQ timing of the TDD SCC further comprises: determining the uplink HARQ timing of the TDD SCC such that the aggregate of 1) a number of subframes between the corresponding uplink transmission and corresponding ACK/NAK indicators, and 2) a number of subframes between ACK/NAK indicators and HARQ process retransmissions without additional grant being received in a downlink control channel transfer corresponds to the number of subframes in the frame period of the TDD SCC; and characterised by communicating with a node based on the identified scheduling timing and on the determined uplink HARQ timing of the TDD SCC, without an additional grant being received in a downlink control channel after the ACK/NAK indicators and before the HARQ process retransmissions. determining a downlink/uplink, DL/UL, configuration for the TDD-SCC; identifying a scheduling timing between a first uplink grant and a corresponding uplink transmission for the TDD SCC based on a scheduling time of the FDD PCC; determining an uplink hybrid automatic repeat request, HARQ, timing of the TDD SCC based at least in part on a frame period of the TDD SCC, wherein a number of subframes in the frame period of the TDD SCC is determined by the DL/UL configuration for the TDD-SCC, and determining the uplink HARQ timing of the TDD SCC such that the aggregate of 1) a number of subframes between the corresponding uplink transmission and corresponding ACK/NAK indicators, and 2) a number of subframes between ACK/NAK indicators and HARQ process retransmissions without additional grant being received in a downlink control channel transfer corresponds to the number of subframes in the frame period of the TDD SCC; and characterised by 1) a number of subframes between the corresponding uplink transmission and corresponding ACK/NAK indicators, and 2) a number of subframes between ACK/NAK indicators and HARQ process retransmissions without additional grant being received in a downlink control channel transfer corresponds to the number of subframes in the frame period of the TDD SCC; and characterised by communicating with a node based on the identified scheduling timing and on the determined uplink HARQ timing of the TDD SCC, without an additional grant being received in a downlink control channel after the ACK/NAK indicators and before the HARQ process retransmissions.