Radio communication apparatus and radio communication method used in mobile communication system

A radio communication apparatus used in a mobile communication system, comprising:

• a unit configured to transmit a user data channel including a sequence number;
• a unit configured to receive an error detection result indicating an affirmative or a negative result with respect to a transmitted first packet;
• a unit configured to receive, after a receiving side detects that a control channel has not been correctly received in the past based on a process number and new packet identification information of a second packet transmitted first after the first packet is transmitted, an indicator when the second packet is transmitted, the indicator consisting of a system frame number corresponding to a latest control channel having been correctly received;
• a unit configured to store attribute information including the sequence frame number and the sequence number corresponding to transmitted packets;
• and
• a unit configured to specify the sequence number of a packet that has not been correctly transmitted in the past based on the attribute information by using a system frame number preceding the system frame number at which the second packet is transmitted and re-transmit the packet.

A radio communication method used in a mobile communication system, comprising:

• a step of transmitting a user data channel including a sequence number from a transmitter to a receiver and determining a system frame number, a process number, and new packet identification information by the receiver;
• a step of detecting whether a first packet received by the receiver includes an error and transmitting a report of the detected result indicating an affirmative or a negative result to a transmitter side;
• a step of detecting whether a control channel has not been correctly received in the past based on the process number and the new packet identification information of a second packet transmitted after the first packet;
• a step of generating an indicator consisting of the system frame number corresponding to a latest control channel having been correctly received;
• a step of reporting the system frame number of the indicator at which the second packet is transmitted to the transmitter side;
• a step of storing attribute information including the sequence frame number and the sequence number corresponding to the transmitted packets;
• a step of specifying the sequence number of a packet that has not been correctly transmitted in the past based on the attribute information by using a system frame number preceding the reported system frame number at which the second packet is transmitted and retransmitting the packet, wherein
• a transmission timing at which the control channel has not been correctly received by the receiver is identified based on the preceding system frame number.