Research On Retransmission Mechanism And Scheduling Method For Highly Reliable Data Stream In Wireless Sensor Networks

The development of wireless sensor networks provides promising solutions for a variety of application scenarios in wireless sensing and wireless communication. In some special application, such as industrial system, high reliability and low latency are necessary for wireless sensor networks. However, complex usage of channel in these applications has induced serious interferences in wireless sensor networks. This is a challenge for the transmission of highly reliable data stream in applications of wireless sensor networks.In this thesis, the key technology of MAC layer in wireless sensor networks is studied. The main contributions and innovations are as follows:The time-aware retransmission mechanism (TARM) under strong reflected channel interference is proposed. In wireless sensor networks,retransmission mechanism of IEEE 802.15.4 protocol can not adapt to the strong reflected channel interference in the closed environment. Due to the bandwidth limitation of wireless channel resources, channel interference is likely to cause data collisions between network devices.According to the number of continuous data frame transmission-successes and the number of continuous data frame transmission-failures, TARM adjusts time delay of each frame to reduce the influence of reflected interferences and avoid signal-collisions with the same frequency wireless devices as much as possible. In the aluminum metal enclosed box, the successful transmission rate, goodput and transmission delay of network are tested and analyzed. The experimental results show that the proposed retransmission mechanism can achieve reliable communication under the strong reflected channel interference.A MAC protocol of hybrid channel access scheme in low latency deterministic networks is proposed. In wireless sensor networks, the contention-based CSMA mechanism can not satisfy the real-time application requirement of the low latency deterministic networks. Based on the characteristics of low latency deterministic networks,a MAC protocol of hybrid TDMA and CSMA is designed. In this thesis, Network topology is a star topology. In the TDMA timeslot phase, the width of a TDMA slot is reduced, and the whole beacon interval is reduced. The retransmission mechanism using CSMA/CA improves reliability of the network. In this thesis, a mathematical model is proposed to analyze the hybrid channel access scheme. The simulation results show that the hybrid channel access scheme outperforms the legacy slotted CSMA/CA scheme and can satisfy the application requirements of low latency deterministic networks.