A communication apparatus functioning as a mobile station may include a message receiver, a communication range determination unit, an existence determination unit, and a management signal output unit. The message receiver receives from a first control station a message that indicates a second control station. The communication range determination unit determines whether the apparatus is in a region within the second control station communication range. If the apparatus is in a region within the second control station communication range, then the existence determination unit determines whether there is another mobile station that belongs to a communication group of the first control station and exists in a region outside the second control station communication range. If the other mobile station is determined to exists, then the management signal output unit outputs a management signal as a third control station for constructing a communication group including the other mobile station.