Cooperative communication techniques have been proposed in order to improve the quality of the received signals at the receivers by using the diversity added by duplication of signals sent by relays situating between each transmission pair. This paper proposes a new on-demand cooperative transmission technique concerned with the interoperability issues between nodes with cooperative functionality and legacy nodes. Based on the standard IEEE 802.11, the proposed method can switch its transmission mode for each data frame between a cooperative mode and a non-cooperative mode automatically. Moreover, it can work with the IEEE medium access method in the basic mode and in the optional RTS/CTS mode. An original method is proposed, where the relay node acts as a proxy that is in charge of data retransmissions when needed. Interest of the proposition is to improve the transmission performance by decreasing the number of retransmissions due to frame errors. Moreover, the proposition avoids inappropriate routing processes that are costly in time and bandwidth. Evaluation of the proposition is done by simulation. Analysis of the results is mainly based on the Packet Delivery Ratio (PDR) and on the Number of Route Discovery and Maintenance (NRDM) per second.