A technique is disclosed which achieves both a reduction of the power consumption and an efficient access control at each of wireless nodes in a wireless communication system. According to this technique, a given period at the beginning of which a beacon is transmitted from a gateway (GW) (100) is specified that it is divided into an active interval during which each wireless node (P2P tag) transmits/receives frames and a sleep interval during which the frame transmission/reception operations are inactive. Further, the active interval is divided into a plurality of timeslots having a fixed length, and in particular, divided into intervals during which different types, that is, the GW, fixed nodes (P2P-S tags) and mobile nodes (P2P-M tags) may perform their respective frame transmissions. Each P2P tag selects, from the intervals of its own type, a timeslot at random and uses the selected timeslot to be on standby for a random standby time and then transmit a frame including information to be used for determining the ID of that P2P tag, the selected timeslot and the standby time.