Patent ID: 8326300

Claim:
A mobile communication method in which, during handover of a mobile station, an exchange including a first protocol function to function as a first protocol and a second protocol function to function as a second protocol being a lower layer than the first protocol transmits a second protocol message containing a first protocol message to radio base stations each including a second protocol function to function as the second protocol, and each of the radio base stations transmits the first protocol message to the mobile station including a first protocol function to terminate the first protocol, the mobile communication method comprising the steps of: transmitting, from the first protocol function of the exchange to the second protocol function of the exchange, a first protocol layer message; starting, at the first protocol function of the exchange, a retransmission timer used to determine a retransmission timing of the first protocol layer message, when transmitting the first protocol layer message to the second protocol function of the exchange; transmitting, from the second protocol function of the exchange to a handover source radio base station, the second protocol message containing the first protocol message; transmitting, from the second protocol function of the exchange to the first protocol function of the exchange, a retransmission request for the first protocol layer message, when receiving a notification, which indicates completion of the handover of the mobile station, from a handover target radio base station, after receiving a second protocol response message, which indicates that transfer of the first protocol message to the mobile station through a radio interface has failed, from the handover source radio base station; retransmitting, from the first protocol function of the exchange to the second protocol function of the exchange, the first protocol layer message, in response to the retransmission request; retransmitting, from the second protocol function to the handover target radio base station, the second protocol message containing the first protocol message; and resetting, at the first protocol function of the exchange, the retransmission timer in response to a notification from the second protocol function of the exchange.