A bidirectional reliable transport mechanism for wireless sensor networks

In wireless sensor networks (WSN), bidirectional end-to-end reliability can only be achieved if every event is reported to the sink and every query (or task) of the sink is delivered to the sensing field successfully. Although sensor networks may provide redundant detection and reporting, this does not guarantee end-to-end reliability. In many applications, the lack of bidirectional reliability may impair event detection and cause inappropriate data collection. In this paper, we introduce a new bidirectional reliable transport mechanism for WSN which addresses both sensor-to-sink and sink-to-sensor reliable transport that is not provided by existing protocols. Bidirectional reliability is achieved by transmitting ACK/NACK packets between the sink and essential sensors that cover the entire sensing field. Essential nodes are selected using a weighted-greedy algorithm based on the residual energy of sensors and rotated in time. Therefore, end-to-end reliable communication is accomplished between the sink and the essential sensors having higher residual energy, while incurring low overhead due to control messages and retransmissions. Moreover, we incorporate a distributed congestion control mechanism. When a congestion is detected, non-essential nodes receive alarm messages from the essential ones, and they temporarily stop reporting events to regulate excessive traffic. Therefore, our approach not only achieves bidirectional end-to-end reliability, but also is effective in congestion control. The performance evaluation of the proposed mechanism is provided by simulation experiments