Patent ID: 8107394

Claim:
A method of data retransmission using a HARQ (Hybrid Automatic Repeat reQuest) scheme in a multi carrier system, the method comprising: receiving, by a user equipment (UE) from a base station (BS), a first grant message including first resource allocation information for an uplink data transmission and a first new data indicator (NDI) indicating transmission of a new uplink data or retransmission of the uplink data; transmitting, by the UE to the BS, the uplink data using the first resource allocation information when the first NDI indicates the new uplink data transmission; receiving, by the UE from the BS, an HARQ acknowledgement message for the uplink data; maintaining, by the UE, the uplink data in a buffer until a predetermined condition is satisfied even though the HARQ acknowledgment message is detected as a positive acknowledgement (ACK) message; receiving, by the UE from the BS, a second grant message including second resource allocation information for the uplink data transmission and a second NDI; setting, by the UE, the HARQ acknowledgement message to a negative acknowledgement (NACK) message when the second NDI is not toggled compared with the first NDI even though the HARQ acknowledgment message is detected as the ACK message; and retransmitting, by the UE to the BS, the uplink data using the second resource allocation information.