An Efficient Retransmission Scheme for Reliable End-to-End Wireless Communication over WSANs

Wireless sensor and actuator network (WSAN) is increasingly recognized as an important technology in the realization of the future Internet of Things (IoT). The ability to cater to the demands of real-time, reliable and resource-constraint communication in industrial areas is highly dependent on efficient scheduling of communication links. Harsh industrial environments make packet retransmission inevitable, which causes the waste of link resource and deteriorates the reliability. Most of researches that focus on real-time and reliable performance underestimate the complexity of packet retransmission. Therefore, this paper proposes an efficient retransmission scheme to guarantee deterministic communication and decrease the resource utilization. We combine deterministic communication with a novel reliable method by proposing a flow-based slot scheduling with a concession timeslot assistant. The proposed concession slot works by using the CCA and the pre-signal to avoid the contention of one channel during the communication on shared links. Furthermore, we use the theory of discrete-time Markov chain to analyze another two randomly backoff-based and flow-based shared link schedules. This study demonstrates that the proposed retransmission scheme can significantly improve the reliability of end-to-end packets delivery and the efficiency of slot utilization, as well as decrease energy consumption. The proposed scheduling is applied in a real factory, where the efficiency of the slot is significantly improved, and a flow reliability of 95.3% under a 12% packet error rate is guaranteed.