Techniques for collision avoidance on a current receiving network node using a half duplex wireless transceiver include, in response to receiving a request to transmit a variable length data message from a first node, transmitting a clear to transmit message that indicates the first node followed by transmitting a physical layer first pilot message. In some circumstances, the techniques include transmitting an acknowledgement message that indicates the first node, only in response to successfully receiving the variable length data message that indicates the first node followed by receiving a physical layer second pilot message. The second pilot message can be detected using either or both of energy detection and preamble detection.