This invention provides a communication system, a repeater terminal in the communication system and a communication method for improving the characteristics in a multi-hop communication by a diversity gain and reduces the power consumption by wasteful retransmission in packet transmission at a wireless terminal. When a transmitter terminal S sends a packet first time, repeater terminals R1-R13 perform a data transmission by retransmission at all the terminals which received the packet. When a transmitter terminal S sends a packet second time, a repeater terminal determines its own contribution based on the hop numbers of the repeating in the packet transmission and the return ACK (or NACK) repeating. The repeater terminal with a high contribution autonomously determines to be in “repeater mode” and the repeater terminal with a low contribution autonomously determines to be in “sleep mode”.