A sensor network includes: a network coordinator that broadcasts a first beacon frame; a sensor device that receives a frame from the network coordinator or transmits a frame to the network coordinator; and at least one repeater that relays the frame of the network coordinator to the sensor device or relays the frame of the sensor device to the network coordinator and that broadcasts a second beacon frame that is synchronized with the first beacon frame, wherein the sensor device is synchronized with the second beacon frame to transmit/receive the frame, the cyclic-superframe includes a plurality of slotted-superframes corresponding to the first beacon frame and the second beacon frame, and the network coordinator, the sensor device, and the repeater operate in a periodically repeated cyclic-superframe structure.