Patent ID: 8812009
Filing Date: 2014-08-19
Classification: H04W

Abstract:
1. A method of maintaining time alignment of a user equipment (UE) in a mobile communication system by performing random access procedures, the method comprising: transmitting a random access channel (RACH) preamble from the user equipment to a network to perform a random access procedure; receiving, by the UE, a random access channel (RACH) response from the network, wherein the RACH response comprises a timing command to enter into a synchronization state; starting, by the UE, a time alignment timer for uplink time alignment when the timing command is received from the network, wherein the time alignment timer is for controlling an uplink synchronization state of the UE; and receiving, by the UE, a contention resolution message from the network to determine whether the random access procedure is successful or not, wherein the UE considers itself as in an asynchronous state if the UE determines that the random access procedure is not successful based on the contention resolution message, wherein, when the UE has a dedicated random access preamble, the UE performs a random access procedure using the dedicated random access preamble regardless of whether the UE is in the uplink synchronization state or the uplink asynchronous state.