Abstract: A cell search method for handover between an asynchronous mobile communication system's base station and a synchronous mobile communication system's base station. A border base station, which is an asynchronous base station neighboring a synchronous mobile communication network, acquires information on a GPS satellite time, a reference time of the synchronous mobile communication network, generates base station frame number (BFN) synchronized to the satellite time and a system frame number (SFN) having a predetermined offset for the BFN for each cell, generates a system information block including a difference value between the BFN and the SFN, and transmits the system information block over a common channel along with the SFN.