Patent ID: 8630248

Claim:
A method of performing hybrid automatic repeat request (HARQ) by a user equipment in a multiple carrier system, the method comprising: receiving a first downlink grant on a downlink control channel through a first component carrier, the first downlink grant including a first HARQ process index (HID) indicating an HARQ process index and a first new data indicator (NDI) indicating a new transmission or a retransmission; receiving a downlink transfer block on the downlink data channel indicated by a resource allocation in the first downlink grant through the first component carrier; transmitting a NACK signal for the downlink transport block; receiving a second downlink grant on the downlink control channel through a second component carrier different from the first component carrier, the second downlink grant including a second HID indicating same HARQ process as the first HID and a second NDI indicating a retransmission of the downlink transfer block which has been transmitted through the first component carrier; and receiving the retransmission of the downlink transfer block through the second component carrier.