Abstract
Wireless sensor networks (WSNs) are widely applied in industrial manufacturing systems. By means of centralized control, the real-time requirement and reliability can be provided by WSNs in industrial production. Furthermore, many approaches reserve resources for situations in which the controller cannot perform centralized resource allocation. The controller assigns these resources as it becomes aware of when and where accidents have occurred. However, the reserved resources are limited, and such incidents are low-probability events. In addition, resource reservation may not be effective since the controller does not know when and where accidents will actually occur. To address this issue, we improve the reliability of scheduling for emergency tasks by proposing a method based on a stealing mechanism. In our method, an emergency task is transmitted by stealing resources allocated to regular flows. The challenges addressed in our work are as follows: (1) emergencies occur only occasionally, but the industrial system must deliver the corresponding flows within their deadlines when they occur; (2) we wish to minimize the impact of emergency flows by reducing the number of stolen flows. The contributions of this work are two-fold: (1) we first define intersections and blocking as new characteristics of flows; and (2) we propose a series of distributed routing algorithms to improve the schedulability and to reduce the impact of emergency flows. We demonstrate that our scheduling algorithm and analysis approach are better than the existing ones by extensive simulations.
Highlights
Wireless sensor network (WSN) technology is widely applied in process industries because of its advantages of low cost and ease of use [1]
We propose an optimal algorithm for emergency flows (optimal path scheduling algorithm (OPSA)); by iterating over all scenarios, the controller can determine the optimal path for an emergency flow
We introduce optimal benefit-based stealing scheduling algorithm (OBSSA) based on three considerations: (1) we first define intersections and blocking and analyze the characteristics of the network ; (2) based on these network characteristics, we propose a method that can guarantee that an emergency flow will arrive at its destination before its deadline; and (3) we design a data structure for the additional memory overhead
Summary
Wireless sensor network (WSN) technology is widely applied in process industries because of its advantages of low cost and ease of use [1]. The controller would be required to allocate paths for all possible accident nodes This is impractical in a WSN for the following reasons: (1) the network has limited channels and transmission resources, and it must still satisfy the performance requirements under no-accident conditions; (2) it is not desirable to abandon all regular flows since they serve useful purposes in the factory; and (3) wireless sensor nodes cannot afford high energy overheads. It is meaningful, and very urgent to study how to cope with emergencies or accidents in industrial WSNs. This work systematically investigates the handling of occasional emergency tasks in industrial.
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