A base station system includes a base station device (1), a wireless transmission device (2) and a data transfer device (3), each of which can be installed outdoors. Enclosures (12, 22 and 32) of the devices (1-3) each provide a degree of protection from water and dust ingress necessary for being installed outdoors. The enclosure (12) of the base station device (1) accommodates electronic equipment (11) functioning as a base station. The enclosure (22) of the wireless transmission device (2) accommodates electronic equipment (21) functioning as a radio station to perform wireless transmission with the other device for connecting the base station device (1) to a mobile backhaul network. The enclosure (32) of the data transfer device (3) accommodates electronic equipment (31) functioning as a router or a switch to transfer data packets or data flames between the base station device (1) and the wireless transmission device (2). This eliminates the need for construction of a building/shelter to install the base station system.