Study Of Deterministic Scheduling Methods Based On Data Packet Aggregation Supporting For Industrial Wireless Networks

Industrial wireless networks are key technologies which are used for data exchange among industrial automation devices due to its low cost,flexible deployment,high reliability,and easy maintenance.It plays an important role in monitoring and controling industrial field devices.To satify the real-time performance and the deterministic requirement for the industrial wireless networks,the data flows must be transmitted to the destination device under the strict deadlines.If any one packet misses its deadline,the productivity of plant may be affected or even industrial accidents may happen.Deterministic scheduling technology aims to allocate appropriate the time slots and channels resources for data flows to meet the deadline constraints of flows.There are many tranmisstion conflicts for links when the data flows are close to the gateway.Considering that conflict links need to be allocated in the different time slots,this would use a lot of time slot resource.And the unscheduled links obtain fewer time slots.This situation may result in scheduling failed.If the network devices support the function of data packet aggregation,it can reduce transmission conflicts to improve schedulable ratio.To overcome these problems,it is necessary to design the determination scheduling methods for supporting data packet aggregation.The main work of this dissertation is as follows:1.This dissertation summarizes the current research of deterministic scheduling in industrial wireless networks,and analyzes the existing problems.Meanwhile,the relevant knowledge about the industrial wirelss networks is introduced.2.There will be a lot of transmission conflicts among the links when the data flows are close to the gateway.In order to improve the schedulabele ratio of the networks under the above scenario,this dissertation proposes three deterministic scheduling methods that support data packet aggregation,namely,packet aggregation scheduling method based on conflict laxity,deterministic scheduling method based on maximum aggregation packets priority,and deterministic scheduling method considering packet aggregation combination and conflict laxity.To improve the schedulable ratio of networks,the proposed methods adopt the pattern of main link and additional link and schedule the links of flows through the different data packet aggregation ways.3.The proposed deterministic scheduling methods have been tesed from performance aspects based on the simulation platform.And the simulation results have been analyzed in detail.Test results show that the proposed deterministic scheduling methods can meet the end-to-end transmission requirements of data flows and improve the real-time performance of the network.