| With the development of wireless communication technology,especially the5 th Generation Mobile Communication Technology(5G)in recent years,the spatial scale that the wireless remote-control systems can span has got rid of the limitations of wired communication systems.The wireless remote-control systems represented by WNCS have the characteristics of simple deployment,convenient maintenance,and strong versatility.Therefore,they have been widely used in wireless remote-control scenarios,such as far-sea monitoring and drone control.WNCS in different application scenarios may adopt different communication scheduling strategies.Classical scheduling strategies include continuous scheduling and alternate scheduling strategies.As an important part of the entire WNCS,different communication scheduling strategies have a significant impact on the upper limit of the overall system control performance.Based on the analysis of the exiting WNCS communication scheduling strategies,this paper aims to improve the timeliness of the system and to enhance the stability of the controlled physical process by improving the existing WNCS communication scheduling strategy.Furthermore,a higher-performance WNCS communication scheduling strategy for applications with propagation delay is designed.Considering that the wireless communication process in the remote control system has typical sequential decision-making characteristics,this article starts from the scenario of no propagation delay,and will model the WNCS wireless communication process with both uplink-downlink propagation delays and channel transmission errors as Markov Decision Process(Markov Decision Process,MDP).Compared with the existing models,the model built in this paper has the characteristics of describing the WNCS system state transition process more universally and intuitively.Based on the MDP modeling,this paper presents the sufficient condition for the existence of optimal scheduling strategies when both the uplink and downlink propagation delay and the channel error rate are considered.This condition can guide the task of scheduling strategy design in scenarios that are far more complex than those existing models.Under the premise of the establishment of this condition,this article firstly applies Hybrid Automatic Repeat Request(HARQ)technology to improve the existing communication scheduling strategy under no propagation delay scenarios,and obtains a joint uplink and downlink scheduling strategy combined with uplink HARQ.Subsequently,this article optimizes the MDP modeling method for the WNCS communication scenario with both propagation delays and channel errors,then uses the dynamic programming algorithm to obtain the optimal scheduling strategy based on the lookup table.After that,this paper further designs the sub-optimal scheduling strategy based on neural network to reduce the space complexity of the optimal scheduling strategy.Finally,this paper proposes a sub-optimal strategy design scheme based on the shortest control loop to further improve the application feasibility.Numerical simulations show that compared with existing strategies,the scheduling strategies proposed in this paper have significant performance improvements. |
