Competition: RedFixHop with Channel Hopping.

A constructive interference (CI) based flooding mechanism, using hardware-generated acknowledgments (ACKs), is proposed to achieve highly reliable source-to-sink communication of very short critical packets within a wireless sensor network (WSN) working in harsh environments. CI is achieved only when the senders synchronize their packet transmissions with sub-microsecond precision. In order to achieve the required synchronization accuracy, the packet retransmissions at the relay nodes are triggered by using hardware ACKs. To further increase packet reception probability, channel diversity is exploited using a predefined hopping sequence. The protocol performance is experimentally evaluated by implementing it using IEEE 802.15.4 radio transceivers.