Communication apparatus, controlling method for emission and threshold, radio network system

Reception power value of the received signal threshold of the controller 5 notifies the carrier detector 6, then controls various portions, such that when receiving a transmit signal received power exceeds the threshold value from the threshold Rth of the controller 6 is, delayed transmission signal . Demodulator 3 included in the notification transmission source of the received signal threshold controller 6. Modulator 4 notifies the controller 6 to emit a threshold signal destination. The controller 6 receives the threshold power value of the signal received from the destination carrier detector 5 to output as the threshold value Rth.