Study Of Link Reliability And Communication Schedule For EPA Wireless Real-time Industrial Network System

The prime requirement of industrial wireless is reliable and real-time communication quality. Aiming at these demands, a cluster-tree based prototype wireless network is presented in this thesis, named EPA wireless. After that, a wireless communication macro-cycle and the guideline of corresponding time-slots usage and media access schedule for each wireless device are also proposed.Under the macro-cycle based communication schedule, our study focuses on the reliable transmission problem of a single wireless message in the first place. Based on large experimental data, a link quality estimator is developed in this thesis, which is used in network topology organization and link quality estimation during message routing, satisfying the requirement of a reliable process data delivery.Moreover, to deal with the schedule problem of multiple devices' data transmission within a macro-cycle for EPA wireless, a time synchronization method is proposed to avoid timeslot collision. For multi-hop wireless networks, our time synchronization method is based on single-message delivery. Within a single-hop, time synchronization among master and slaves can be achieved precisely through the deliver of just a single broadcast message, maximally saving the network resources.After that, a set of improved timeslot assignment algorithm for the circle period of communication macro-cycle are also present, which can guarantee real-time transmission and a flexible macro-cycle. The timeslot assignment scheme covers three frequently used working modes in practical applications. The shortest frame formed can guarantee real-time communication and is also facilitated for message and slot integration during message routing, since timeslots allocated to a single node are continuous. During allocation processes, the algorithms are distributed and light-weighted. The experiment resulted from a prototype system shows that our scheme can achieve a good reliability. While inheriting high reliability performance of traditional TDMA, these algorithms can achieve low-latency data transmission with minimized number of conflict-free timeslots.