A wireless communication apparatus, system, method and computer readable medium therefor for transmission between a parent node and a child node are provided. The child node transmits a first packet to the parent node via point-to-point transmission. When the parent node tries to transmit a second packet to the child node, a synchronization signal is transmitted first and then the second packet is transmitted to the child node via broadcast transmission after a certain period. If the child node fails to receive the second packet during the certain period, the child node sends a signal to the parent node. The parent node re-transmits the second packet to the child node via point-to-point transmission.