A communication device, comprising: a receiving unit configured to receive a frame transmitted by another terminal; a length information acquiring unit configured to acquire length information related to the frame from the received frame on a basis of information related to a data rate and information related to a frame length included in the received frame; a transmission frame deciding unit configured to decide a length of a transmission frame on a basis of the acquired length information; the communication device characterised by further comprising: a signal determining unit configured to determine whether or not the received frame is a signal transmitted from the other terminal belonging to another network different from a network to which the communication device belongs on a basis of identification information included in the received frame; wherein the signal determining unit is configured to determine a reception power of a signal transmitted from the other terminal belonging to the other network, wherein the transmission frame deciding unit is configured to determine that a medium is in an idle state in a case in which the signal determining unit determines that the received frame is the signal transmitted from the other terminal belonging to the other network, and the reception power of the signal transmitted from the other terminal belonging to the other network is equal to or lower than a threshold value related to the signal transmitted from the other terminal belonging to the other network, and the communication device includes a transmission power control unit configured to control a transmission power of the transmission frame in accordance with the threshold value related to the signal transmitted from the other terminal belonging to the other network. a receiving unit configured to receive a frame transmitted by another terminal; a length information acquiring unit configured to acquire length information related to the frame from the received frame on a basis of information related to a data rate and information related to a frame length included in the received frame; a transmission frame deciding unit configured to decide a length of a transmission frame on a basis of the acquired length information; the communication device characterised by further comprising: a signal determining unit configured to determine whether or not the received frame is a signal transmitted from the other terminal belonging to another network different from a network to which the communication device belongs on a basis of identification information included in the received frame; wherein the signal determining unit is configured to determine a reception power of a signal transmitted from the other terminal belonging to the other network, wherein the transmission frame deciding unit is configured to determine that a medium is in an idle state in a case in which the signal determining unit determines that the received frame is the signal transmitted from the other terminal belonging to the other network, and the reception power of the signal transmitted from the other terminal belonging to the other network is equal to or lower than a threshold value related to the signal transmitted from the other terminal belonging to the other network, and the communication device includes a transmission power control unit configured to control a transmission power of the transmission frame in accordance with the threshold value related to the signal transmitted from the other terminal belonging to the other network. a signal determining unit configured to determine whether or not the received frame is a signal transmitted from the other terminal belonging to another network different from a network to which the communication device belongs on a basis of identification information included in the received frame; wherein the signal determining unit is configured to determine a reception power of a signal transmitted from the other terminal belonging to the other network, wherein the transmission frame deciding unit is configured to determine that a medium is in an idle state in a case in which the signal determining unit determines that the received frame is the signal transmitted from the other terminal belonging to the other network, and the reception power of the signal transmitted from the other terminal belonging to the other network is equal to or lower than a threshold value related to the signal transmitted from the other terminal belonging to the other network, and the communication device includes a transmission power control unit configured to control a transmission power of the transmission frame in accordance with the threshold value related to the signal transmitted from the other terminal belonging to the other network.