An Efficient Data Transmission Protocol in a Wireless Sensor-Actuator Network

In a wireless sensor-actuator network (WSAN), sensor nodes and actuator nodes are interconnected with wireless channels. Messages sent by sensor nodes might be lost due to collision and noise if multiple sensor nodes simultaneously send the messages in a wireless channel. In sensing applications, sensed values are in nature required to be delivered to actuator nodes with some time constraints. If a message is detected to be lost by some receiver nodes, the sender node retransmits the message to the receiver nodes. It takes at least three rounds to detect and retransmit a lost message since the message is sent. The more number of messages are retransmitted, the more number of messages collide. We have to reduce the number of messages retransmitted to realize the efficient data transmission. We newly propose a redundant data transmission (RT) protocol where data in a message m₁ is redundantly forwarded to the destination node by another message m₂ sent by the receiver node of the message m₁. Even if the message m₁ is lost, the destination node can receive the data in the message m₂ if the destination node receives the message m₂ since the message m₂ carries the data in the message m₁. We evaluate the RT protocol compared with the CSMA protocol in terms of how much sensing data a node can receive in presence of messages loss