Abase station, which serves as a first base station, the base station comprising: a user selection unit, configured to select first user equipment, UE, after receiving a time difference request message sent by a central controller, wherein the central controller performs information exchange with the first base station and a second base station; a random access preamble management unit, configured to allocate a first random access preamble to the first UE selected by the user selection unit, and send the first random access preamble to the second base station, so that the second base station starts random access preamble detection after acquiring the first random access preamble, wherein the first random access preamble is a non-contention based random access preamble, and the first random access preamble is used by the first UE to initiate active random access to the first base station; a random access preamble detection unit, configured to detect the first random access preamble used by the first UE to initiate the active random access; a time information acquiring unit, configured to acquire a first receiving moment and a second receiving moment, wherein the first receiving moment is a moment when the random access preamble detection unit detects the first random access preamble, and the second receiving moment is a moment when the second base station detects the first random access preamble; a time difference calculation unit, configured to calculate the first time difference based on the first receiving moment and the second receiving moment; and a time difference sending unit, configured to send the first time difference acquired by the time difference calculation unit to the central controller, wherein the first base station is a reference base station, and the second base station is a non-reference base station. a user selection unit, configured to select first user equipment, UE, after receiving a time difference request message sent by a central controller, wherein the central controller performs information exchange with the first base station and a second base station; a random access preamble management unit, configured to allocate a first random access preamble to the first UE selected by the user selection unit, and send the first random access preamble to the second base station, so that the second base station starts random access preamble detection after acquiring the first random access preamble, wherein the first random access preamble is a non-contention based random access preamble, and the first random access preamble is used by the first UE to initiate active random access to the first base station; a random access preamble detection unit, configured to detect the first random access preamble used by the first UE to initiate the active random access; a time information acquiring unit, configured to acquire a first receiving moment and a second receiving moment, wherein the first receiving moment is a moment when the random access preamble detection unit detects the first random access preamble, and the second receiving moment is a moment when the second base station detects the first random access preamble; a time difference calculation unit, configured to calculate the first time difference based on the first receiving moment and the second receiving moment; and a time difference sending unit, configured to send the first time difference acquired by the time difference calculation unit to the central controller, wherein the first base station is a reference base station, and the second base station is a non-reference base station.