a period from a start of the timer to a stop of the timer and sets a half of the period or half time in transmission and reception as an rtt in this case the rtt measurement unit 137 may measure the rtt considering an offset value an offset frame or the like for a slot position of the user data in a radio frame then the small cell base station 100 2 determines the service area 100 s of the small cell base station 100 2 in which the terminal 200 2 stays by using the rtt value s 75 for example a position of the terminal 200 2 staying in the service area 100 s is determined as follows that is the small cell base station 100 2 and the terminal 200 perform sampling on a radio signal which is transmitted and received at a sampling frequency of 30 72 mhz in this case a transmission period of time corresponding to one cycle of the radio signal is 32 55 ns 1 30 72m if a transmission period of time of an electromagnetic wave in the air is set to 5 ns m accuracy of about 6 5 m u2245 32 55 5 for the radio signal may be secured if the radius of the service area 100 s is set to 300 m the radium of the service area 100 s is divided into 46 u2245 300 6 5 areas and the small cell base station 100 2 may determine whether or not the terminal 200 2 is positioned in the divided areas fig1 illustrates a division example of the service area 100 s in which division is performed in this manner.