| Wireless Sensor Networks(WSNs)have received great attention in the field of industrial monitoring and control due to their low cost,flexibility and wide deployment.International Society of Automation divides applications into monitoring,control and safety according to the requirements of network performance.The latest report on Industrial Wireless Sensor Networks(IWSNs)of market research firm ON World and the special review of IWSNs technology in IEEE flagship journal Proceedings'2016 pointed out that IWSNs are currently used to monitoring applications with lower network performance requirements.There are still many challenges in advanced applications such as real-time monitoring and safety.It is urgent to carry out in-depth research,which is an important direction for future development.Therefore,this dissertation mainly conducts researches on new network architecture and link resources scheduling in IWSNs,which focus on real-time monitoring,production safety and mobility.The main achievements and innovations of this paper are as follows:1.The idea of smart collaborative network is applied and a resource adaptation IWSNs architecture is designed to support harsh requirements of network performance in advanced industrial applications.Through the fine division of network resource components,a resource adaptation protocol and a mechanism of separation between control and data channels are designed to achieve efficient resource adaptation and cater to the network demand of advanced applications.Meanwhile,we implement a prototype system in practical industrial applications and provide deployment and verification for the research content of subsequent chapters.2.An efficient retransmission resources scheduling algorithm for single path based on the concession time slot is proposed to improve the reliability of multi-hop transmission in IWSNs.First,the low reliability of contention mechanism based on shared time slot is analyzed.Then,the concession time slot is designed,which adopts the mechanisms of clear channel assessment and channel preemption.Next,a path-based continuous time slot scheduling is proposed with the considerations of the continuity and idle slots for multi-hop retransmission.Finally,reliability of different scheduling policies is analyzed and the experiments are conducted in the environments with different link reliability.The results show that the reliability of the proposed algorithm is improved more obviously with the increase of link loss rate.Moreover,there are the higher time slot utilization and lower energy consumption while obtaining the same data delivery ratio.3.Multipath retransmission can effectively improve the reliability of IWSNs,however it causes the low schedulable ratio due to the real-time requirement of industrial applications.Therefore,a resources scheduling with interference avoidance based on multiple constraints is proposed.First,the constraints of slots and channels scheduling are analyzed under the condition of multiple periods and limited channel resources.A transmissions release algorithm is proposed with the consideration of the routing order issue.Through the analysis of interferences brought by multiple periods and paths,an interference avoidance scheduling is proposed based on multiple constraints by adopting rate monotonic policy,multiple sinks and reuse shared time slots.The simulations prove that the proposed algorithm can support more nodes and have higher schedulability.Meanwhile,the practical experiments prove that the algorithm can guarantee the determinacy of data transmission and reduce the average transmission delay.4.Industrial applications of safety demand the network to handle bursty urgent data with the highest priority,which require IWSNs to support different priority data processing.However,existing researches of IWSNs lack of supporting QoS.Therefore,an event-triggered priority access control mechanism is proposed.First,an event-triggered fail-safe model is established for a safety applications.Then a priority access control mechanism is proposed by designing the slot of periodic transmission,emergency alert and emergent transmission,which achieves event trigger,resources preemption and real-time transmission.The mechanism fundamentally solves the resources scheduling problem with the coexistence of periodic and bursty data.The real-time performance is theoretically analyzed and the contrast experiments are conducted on a fail-safe system in a welding factory.The results prove the real-time performance and indicate that the bandwidth can be greatly reduced in the case of the long reporting period of fail-safe devices.5.Currently,IWSNs are mainly used in static scenarios,but supporting mobility is the trend of advanced industrial applications in the future.Therefore,a seamless mobile handoff scheme based on fuzzy logic control is proposed to reduce lost and overdue packets caused by nodes movement.Due to the limited ability of a node,the easily obtained data link parameters is analyzed by practical tests to construct three handoff triggering parameters,and a mobile handoff triggering scheme is proposed to reduce loss caused by mis-switching and late switching.In order to reduce the number of overdue packets and link registrations of mobile nodes,a seamless mobile handoff algorithm is proposed by using segmented time slot scheduling scheme.This algorithm enables nodes to dynamically schedule shared communication resources and achieve data delivery during movement.Moreover,it avoids frequent link registration of the mobile nodes by evaluating mobile status during the movement.Experiments indicate that the proposed scheme can effectively reduce the number of lost and overdue packets and energy consumption of mobile nodes,compared with traditional handoff mechanism. |
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