An apparatus includes a unit receiving a first-radio signal indicating a state in which transmission by a SDMA scheme is allowed, a unit determining whether a transmission state is a first state (the SDMA scheme is available), or a second state (the SDMA scheme is unavailable), a unit transmitting a radio signal using the SDMA scheme, when it is determined that the first state continues for the first-time period, and a unit setting a third-time period, when the first state fails to continue for the first-time period, the third-time period being obtained by subtracting, from the first-time period, a second-time period ranging from when carrier sense is started to when the transmission state is determined to be the second state, wherein when the first-radio signal is received after the third-time period is set, it is determined whether the first state continues for the third-time period.