1. A method for a user equipment (UE) in a wireless communication system, the method comprising:receiving information, which includes a random access preamble identifier (RAPID) as a dedicated preamble and an index of a second cell, at a first cell from a network;
transmitting a random access preamble at the first cell to the network, when it is determined that the random access preamble does not use the RAPID as the dedicated preamble; and
receiving a random access response at the second cell from the network,
wherein the first cell is a first serving cell on a licensed carrier, and
wherein the second cell is a second serving cell on an unlicensed carrier.