Add-on base station for cellular network expansion

An add-on base-station (41, 42, 43) comprising: a wireless RF channel (51) including an antenna (61) and an RF unit (62) adapted to connect to a first mobile user (11); channel electronic means (53) for connecting the wireless RF channel (51) to a second channel connected to an Internet network (24); and a call controller (54) adapted to supervise operation of said channel electronic means (53); wherein said add-on base station (41, 42, 43) is adapted to connect the first mobile user (11) to the Internet network (24) via an IP connection (52, 65); the add-on base station (41, 42, 43) is comprised in a system which also comprises at least one coordination center (3) connected to the Internet network (24); the add-on base-station (41, 42, 43) is adapted to contact the coordination center (3) via the Internet network (24) prior to the call; the add-on base-station (41, 42, 43) has a unique identity; and the add-on base station (41, 42, 43) is further adapted to either : - report its location, known according to a GPS device inserted within said add-on base station such that the location of the add-on base station (41, 42, 43) is made known to the coordination center (3); - or forward to said coordination center (3) information regarding an identity of a received base station and a power level of a reception, such that the coordination center (3) can estimate the location of the add-on base station (41, 42, 43) using this information.