Handover method, radio base station, and mobile station

A radio base station operable as a first radio base station when a handover of a mobile station connected to a first cell under the first radio base station to a second cell under a second radio base station is performed, the radio base station comprising:

• a transmission unit configured to notify the second radio base station of a HARQ process, wherein
• the transmission unit is configured to transmit a handover instruction signal to the mobile station by using a HARQ process different from the HARQ process notified to the second radio base station.

A handover method of performing a handover of a mobile station connected to a first cell under a first radio base station to a second cell under a second radio base station, comprising the steps of:

• transmitting, by the first radio base station, a handover instruction signal to the mobile station by using any of a predetermined number of HARQ processes usable between the first radio base station and the mobile station;
• and
• transmitting, by the second radio base station, a handover instruction signal to the mobile station by using a special HARQ process different from the predetermined number of HARQ processes.

A radio base station operable as a second radio base station when a handover of a mobile station connected to a first cell under a first radio base station to a second cell under the second radio base station is performed, the radio base station comprising:

• a transmission unit configured to transmit a handover instruction signal to the mobile station by using a special HARQ process different from a predetermined number of HARQ processes usable between the first radio base station and the mobile station.

A mobile station, wherein

• the mobile station is configured, when the mobile station performs a handover from a first cell under a first radio base station to a second cell under a second radio base station, to receive a handover instruction signal from the first radio base station by using any of a predetermined number of HARQ processes usable between the mobile station and the first radio base station, and to receive a handover instruction signal from the second radio base station by using a special HARQ process different from the predetermined number of HARQ processes, and
• a buffer corresponding to the special HARQ process is flushed in any one of cases where a MAC layer is initialized, where a measurement report is transmitted to the first radio base station, where any of MAC-ACK and RLC-ACK in response to the measurement report is received from the first radio base station, and where an upper layer activates an “RRC diversity” function.