There has been known a radio communication system configured in assuming that a base station performs radio communication with a mobile terminal (mobile station) included in a device that travels on a predetermined route, such as a train and an automobile. As a method of configurating such a radio communication system, there has been proposed a method of configuring a communicable range (cell) in an elongated shape along a traveling route with a plurality of directional beams using a distributed antenna base station to which a plurality of directional antennas, which is distributed along the traveling route of a mobile device (mobile station), is connected (Non Patent Literature 1). When the shape of the cell is formed to be elongated along the traveling route, a cell length can be increased while interference with another radio communication system is suppressed. Such a distributed antenna system can be implemented in a form in which a plurality of antennas is arranged from one communication modem using a transmission medium such as an optical fiber.
Meanwhile, there has been known a method of measuring (ranging) a distance between a base station and a mobile station as a method of detecting a location of a mobile device, such as detection of a traveling location of a train. As such a method of measuring a distance, there has been known a method of measuring a distance from the time required for communication between a radio device of the distance measuring side (e.g., base station) and a radio device of the distance measured side (e.g., mobile station) (Non Patent Literature 2).