A target base station of a handover procedure performed by a user equipment from a source base station to the target base station, the target base station comprising: a control unit configured to allocate three or more component carriers for the user equipment during the handover procedure, wherein a first component carrier of the three or more component carriers corresponds with a first frequency band, and a second component carrier of the three or more component carriers corresponds with a second frequency band; a radio communication unit configured to: receive a random access preamble from the user equipment on the first component carrier among the three or more component carriers; transmit, to the user equipment on the first component carrier, a random access response including a uplink timing adjustment value; receive, from the user equipment on the first component carrier after the handover procedure, a first uplink transmission adjusted based on the uplink timing adjustment value; on condition that a frequency distance between the first frequency band and the second frequency band is smaller than a predetermined threshold, receive, from the user equipment on the second component carrier after the handover procedure, a second uplink transmission adjusted based on the uplink timing adjustment value, wherein the a random access procedure on the second component carrier is skipped during the handover procedure, or on condition that the frequency distance between the first frequency band and the second frequency band is larger than the predetermined threshold, perform the random access procedure on the second component carrier with user equipment, wherein the transmission timing of the first uplink transmission on the first frequency band and the transmission timing of the second uplink transmission on the second frequency band are adjusted based on the one uplink timing adjustment value, wherein a first bandwidth used for the first uplink transmission on the first frequency band is 1.4 MHz, 3.0 MHz, 5.0 MHz, 10 MHz, 15 MHz, or 20 MHz, wherein a second bandwidth used for the second uplink transmission on the second frequency band is 1.4 MHz, 3.0 MHz, 5.0 MHz, 10 MHz, 15 MHz, or 20 MHz. a control unit configured to allocate three or more component carriers for the user equipment during the handover procedure, wherein a first component carrier of the three or more component carriers corresponds with a first frequency band, and a second component carrier of the three or more component carriers corresponds with a second frequency band; a radio communication unit configured to: receive a random access preamble from the user equipment on the first component carrier among the three or more component carriers; transmit, to the user equipment on the first component carrier, a random access response including a uplink timing adjustment value; receive, from the user equipment on the first component carrier after the handover procedure, a first uplink transmission adjusted based on the uplink timing adjustment value; on condition that a frequency distance between the first frequency band and the second frequency band is smaller than a predetermined threshold, receive, from the user equipment on the second component carrier after the handover procedure, a second uplink transmission adjusted based on the uplink timing adjustment value, wherein the a random access procedure on the second component carrier is skipped during the handover procedure, or on condition that the frequency distance between the first frequency band and the second frequency band is larger than the predetermined threshold, perform the random access procedure on the second component carrier with user equipment, receive a random access preamble from the user equipment on the first component carrier among the three or more component carriers; transmit, to the user equipment on the first component carrier, a random access response including a uplink timing adjustment value; receive, from the user equipment on the first component carrier after the handover procedure, a first uplink transmission adjusted based on the uplink timing adjustment value; on condition that a frequency distance between the first frequency band and the second frequency band is smaller than a predetermined threshold, receive, from the user equipment on the second component carrier after the handover procedure, a second uplink transmission adjusted based on the uplink timing adjustment value, wherein the a random access procedure on the second component carrier is skipped during the handover procedure, or on condition that the frequency distance between the first frequency band and the second frequency band is larger than the predetermined threshold, perform the random access procedure on the second component carrier with user equipment, wherein the transmission timing of the first uplink transmission on the first frequency band and the transmission timing of the second uplink transmission on the second frequency band are adjusted based on the one uplink timing adjustment value, wherein a first bandwidth used for the first uplink transmission on the first frequency band is 1.4 MHz, 3.0 MHz, 5.0 MHz, 10 MHz, 15 MHz, or 20 MHz, wherein a second bandwidth used for the second uplink transmission on the second frequency band is 1.4 MHz, 3.0 MHz, 5.0 MHz, 10 MHz, 15 MHz, or 20 MHz.