//
// Used by the MAC layer to start transmitting a packet.
//
void Phy802_15_4StartTransmittingSignal(
    Node* node,
    Int32 phyIndex,
    Message* packet,
    BOOL useMacLayerSpecifiedDelay,
    clocktype initDelayUntilAirborne)
{
...
    PROP_ReleaseSignal(node,
                       packet,
                       phyIndex,
                       channelIndex,
                       phy802_15_4->txPower_dBm,
                       duration,
                       delayUntilAirborne);
...
}