Patent ID: 8634400

Claim:
A method for transmitting packet data by a transmitter in a mobile communication system, the method comprising: transmitting data segments generated by segmenting a packet data to a receiver; and if a message for requesting retransmission of at least one data segment among the data segments is received from the receiver, retransmitting the at least one data segment to the receiver, wherein the data segments are transmitted by using a frame, the frame includes a first packet data unit (PDU), the first PDU includes at least one multiplexing header and at least one second PDU, each of the at least one multiplexing header includes multiplexing information for a corresponding second PDU, and each of the at least one second PDU includes a header for the second PDU and a payload, and wherein the header for the second PDU includes a sequence number based on a sequence number of a related second PDU, a 1-bit first flag indicating whether a length indicator is included in a corresponding header, the length indicator indicating a length of a corresponding data segment included in the payload, and a 1-bit second flag indicating whether one of another length indicator and the payload is followed.