Mobile communication method, mobile station and radio base station

A mobile communication method comprising the steps of:

• generating, at a mobile station and a serving radio base station serving the mobile station, first verification information by use of a first key, first parameters and an algorithm for “Integrity Protection,” wherein the first parameters are “COUNT,” “bearer ID,” and “direction (DL(Downlink)/UL(Uplink))”;
• generating, at the mobile station and at the serving radio base station, short MAC-I (Message Authentication Code for Integrity) information by extracting predetermined bits of the first verification information;
• transmitting, from the serving radio base station to a neighbor radio base station, the short MAC-I information by use of a handover preparation signal;
• performing, at the mobile station, cell selection processing, and transmitting, from the mobile station to a selected radio base station that manages the selected cell, an RRC-PDU (Radio Resource Control-Protocol Data Unit) for RRC connection re-establishment request through a common control channel, upon detection of a radio link failure in an RRC connection, the short MAC-I information being set in the RRC-PDU for RRC connection re-establishment request, wherein the selected base station is one of the serving base station and the neighbor base station;
• and
• verifying, at the selected radio base station, the RRC-PDU for RRC connection re-establishment request received from the mobile station by use of the short MAC-I information;
• wherein a physical cell ID and a C-RNTI are set in the RRC-PDU for RRC connection re-establishment request.