Patent ID: 8238305

Claim:
A transmission restarting method of restarting transmission of downlink user data to a mobile station in a discontinuous reception state, comprising the steps of: allocating, at a radio base station, a radio resource for downlink data transmission to the mobile station, and notifying, from the radio base station to the mobile station, the allocated radio resource for downlink data transmission; restarting, at the radio base station, transmission of downlink user data to the mobile station by using the allocated radio resource for downlink data transmission; stopping, at the radio base station, transmission of the downlink user data when a predetermined condition is detected; transmitting, from the radio base station to the mobile station, an uplink synchronization request by using the allocated radio resource for downlink data transmission, the uplink synchronization request designating a data series allocated for identifying the mobile station; notifying, from the mobile station to the radio base station, the data series designated by the uplink synchronization request, when successfully receiving the uplink synchronization request; transmitting, from the radio base station to the mobile station, a command for adjusting uplink transmission timing by using the allocated radio resource for downlink data transmission when receiving the data series from the mobile station; restarting, at the radio base station, transmission of the downlink user data to the mobile station by using the allocated radio resource for downlink data transmission, when not receiving the data series from the mobile station until a predetermined period is passed after transmission of the command; and stopping, at the radio base station, transmission of the downlink user data, and transmitting, at the radio base station, any of the uplink synchronization request and the command when the predetermined condition is detected.