Patent ID: 8031692

Claim:
A method for maintaining uplink timing synchronization (sync) in a mobile communication system, comprising: transmitting from a User Equipment (UE) to a Node B an uplink sync request message including a preamble code; receiving at the UE from the Node B an uplink sync response message in response to the request message; adjusting, at the UE, uplink timing according to uplink timing adjustment information included in the response message, and storing the adjusted uplink timing as reference uplink timing for uplink signaling or data transmission at the UE; periodically measuring downlink timing at the UE after storing the reference uplink timing, and calculating a difference between the measured downlink timing and previously stored reference downlink timing at the UE; periodically re-determining the uplink timing at the UE by applying the calculated difference between the measured downlink timing and the previously stored reference downlink timing to the reference uplink timing after each periodically measured downlink timing; receiving a request message for readjustment of the uplink timing at the UE from a Node B that has detected a discrepancy of the uplink timing; readjusting the uplink timing at the UE using uplink timing adjustment information included in the uplink timing readjustment request message, updating the reference uplink timing with the readjusted uplink timing at the UE, and storing the updated reference uplink timing at the UE; and updating a last measured downlink timing as the reference downlink timing at the UE when updating the reference uplink timing, and storing the updated reference downlink timing at the UE.