We Claim:
1. A mobile communication system in which a first base station and a second
base station communicate with a user equipment in parallel and the first base station and
the second base station communicate with a radio network controller in parallel,
wherein in a control plane, the first base station communicates with the user equipment and the first base station communicates with the radio network controller, and
in a user plane, the second base station communicates with the user equipment and the second base station communicates with the radio network controller.
2. The mobile communication system as claimed in claim 1, wherein in the user plane, the second base station communicates directly with the radio network controller.
3. The mobile communication system as claimed in claim 1, wherein in the user plane, the first base station communicates directly with the user equipment and the second base station communicates with the radio network controller via the first base station.
4. The mobile communication system as claimed in claim 3, wherein the first base station distributes, to the user equipment and the second base station, data received from the radio network controller and transmits distributed data to the user equipment and the second base station.
5. The mobile communication system as claimed in claim 3, wherein the first base station rearranges the order of data received from the user equipment and data received from the second base station and transmits rearranged data to the radio network

controller.
6. The mobile communication system as claimed in claim 1, wherein the radio network controller that communicates with the first base station in the control plane is a mobility management device.
7. The mobile communication system as claimed in claim 1, wherein the radio network controller that communicates with the second base station in the user plane is a gateway station.
8. A radio network controller that communicates with a first base station and a second base station in parallel, the first base station and the second base station communicating with a user equipment in parallel,
wherein in a control plane, the radio network controller communicates with the first base station that communicates with the user equipment, and
in a user plane, the radio network controller communicates with the second base station that communicates with the user equipment.
9. A base station that communicates with a user equipment in parallel with
another base station and communicates with a radio network controller in parallel with the
other base station,
wherein in a control plane, the base station communicates with the user equipment and the radio network controller, and
in a user plane, the other base station communicates with the user equipment

and the other base station communicates with the radio network controller.
10. A base station that communicates with a user equipment in parallel with
another base station and communicates with a radio network controller in parallel with the
other base station,
wherein in a control plane, the other base station communicates with the user equipment and the other base station communicates with the radio network controller, and
in a user plane, the base station communicates with the user equipment and the radio network controller.
11. A user equipment that communicates with a first base station and a second
base station in parallel, the first base station and the second base station communicating
with a radio network controller,
wherein in a control plane, the user equipment communicates with the first base station that communicates with the radio network controller, and
in a user plane, the user equipment communicates with the second base station that communicates with the radio network controller.