Base station, mobile station, communication system, and reordering method thereof

A communication system in which a base station sends packets to which numbers indicating order are attached, to a mobile station, the mobile station performs delivery of the packets in order, and handover is performed, comprising:

• a handover source base station provided with a controller that sends configuration information indicating whether forwarding of packets has been executed or not, to the mobile station, wherein
• the mobile station includes:
• a receiver that receives the configuration information indicating whether the forwarding of packets has been executed or not, from the handover source base station;
• and
• a controller that controls delivery of the packets received from a handover target base station at the handover, in order based on the configuration information indicating whether the forwarding of packets has been executed or not, and wherein
• the controller in the handover source base station decides whether the handover source base station forwards packets which have not been sent to the mobile station, out of packets received from a host station, to the handover target base station or not, controls the forwarding of the packets from the handover source base station to the handover target base station at the handover based on the decision, and controls of sending the configuration information indicating whether forwarding of packets has been executed or not, from the handover source base station to the mobile station.