A femtocell in electronic communication with different user equipments includes a setting unit, a subscriber identity module (SIM), a signal processing unit and a monitoring unit. The setting unit sets and establishes a monitoring area to monitor all items of user equipment. The SIM stores a whitelist which includes a plurality of identification (ID) codes corresponding to a plurality of items of user equipment. When the ID code of an item of user equipment is not within the whitelist of the SIM, the signal processing unit controls the monitoring unit to establish and monitor the position of the user equipment to determine whether the user equipment is within the predetermined monitoring area.