A personal subscriber terminal configured to access a plurality of frequency channels for receiving and transmitting protocol data units through said frequency channels comprising: an ordering unit configured to sequentially align a plurality of protocol data units received through a first frequency channel and a second frequency channel in downlink according to sequence number of the plurality of protocol data units; and a reassembling unit configured to reassemble the first protocol data units and the second protocol data units ordered in the ordering unit and generate a service data unit, wherein the terminal is further configured to: designate a frame number to each of the plurality of protocol data units; if a sequence number of the protocol data unit is equal to or larger than a start sequence number and if the sequence number of the protocol data unit is smaller than or equal to a maximum sequence number, store an aligned protocol data unit in a protocol data unit sequence queue; if the sequence number of the protocol data unit is equal to the start sequence number, transmit a protocol data unit to the reassembling unit, increase the start sequence number by 1, and get a protocol data unit having a first sequence number in the protocol data unit sequence queue; determine whether the sequence number of the protocol data unit stored in the protocol data unit sequence queue is equal to the start sequence number; and if the sequence number is equal to the start sequence number, transmit the protocol data unit stored in the protocol data unit sequence queue to the reassembling unit and increase the start sequence number by 1; characterized in that the terminal is further configured to increase the frame number by 1 every frame when designating the frame number, and transmit the protocol data unit that exceeds a maximum frame range among the protocol data unit stored in the protocol data unit sequence queue to the reassembling unit, and update the start sequence with a value obtained by adding 1 to the sequence number of the thus transmitted protocol data unit. an ordering unit configured to sequentially align a plurality of protocol data units received through a first frequency channel and a second frequency channel in downlink according to sequence number of the plurality of protocol data units; and a reassembling unit configured to reassemble the first protocol data units and the second protocol data units ordered in the ordering unit and generate a service data unit, wherein the terminal is further configured to: designate a frame number to each of the plurality of protocol data units; if a sequence number of the protocol data unit is equal to or larger than a start sequence number and if the sequence number of the protocol data unit is smaller than or equal to a maximum sequence number, store an aligned protocol data unit in a protocol data unit sequence queue; if the sequence number of the protocol data unit is equal to the start sequence number, transmit a protocol data unit to the reassembling unit, increase the start sequence number by 1, and get a protocol data unit having a first sequence number in the protocol data unit sequence queue; determine whether the sequence number of the protocol data unit stored in the protocol data unit sequence queue is equal to the start sequence number; and if the sequence number is equal to the start sequence number, transmit the protocol data unit stored in the protocol data unit sequence queue to the reassembling unit and increase the start sequence number by 1; designate a frame number to each of the plurality of protocol data units; if a sequence number of the protocol data unit is equal to or larger than a start sequence number and if the sequence number of the protocol data unit is smaller than or equal to a maximum sequence number, store an aligned protocol data unit in a protocol data unit sequence queue; if the sequence number of the protocol data unit is equal to the start sequence number, transmit a protocol data unit to the reassembling unit, increase the start sequence number by 1, and get a protocol data unit having a first sequence number in the protocol data unit sequence queue; determine whether the sequence number of the protocol data unit stored in the protocol data unit sequence queue is equal to the start sequence number; and if the sequence number is equal to the start sequence number, transmit the protocol data unit stored in the protocol data unit sequence queue to the reassembling unit and increase the start sequence number by 1; characterized in that the terminal is further configured to increase the frame number by 1 every frame when designating the frame number, and transmit the protocol data unit that exceeds a maximum frame range among the protocol data unit stored in the protocol data unit sequence queue to the reassembling unit, and update the start sequence with a value obtained by adding 1 to the sequence number of the thus transmitted protocol data unit.