Toward Real-Time Control in Future Wireless Networks: Communication-Control Co-Design

Abstract

Wireless networks are undergoing a transition from connecting people to connecting things, which will allow human interaction with the physical world in a real-time fashion, e.g., tactile internet, industrial automation, self-driving vehicles, and remote surgery. Therefore, future wireless networks need to support real-time control since it is the essential function enabling such emerging applications. In this article, some fundamental design capabilities needed to realize real-time control in future wireless networks are discussed, with primary emphasis given to communication-control because both communication and control systems have strong dynamics and interdependencies, and they tightly interact with each other. A case study is provided to demonstrate the necessity of such co-design.

Hybrid ARQ in Wireless Packetized Predictive Control

“…Achieving ultrareliable low latency communications (URLLC) [4] is considerably challenging in wireless sensor networks, and even more complicated in the case of short transmission packets [5], which is the typical traffic generated by sensors and actuators within WNCS. Moreover, the usual separate communication and control design is suboptimal, leading to the demand for communication and control co-design [6].…”

“…In terms of reducing the wireless resources needed to meet the reliability requirement in a WNCS, the authors in [6] made a significant progress. They consider the use of Packetized Predictive Control (PPC) [9], in which a controller forecasts future commands that are sent to an actuator, so that commands sent over the wireless link contain not only those for the current time slots, but also for future time slots.…”

“…Results show significant energy savings, however, the focus of [12] is not the case of WNCS, and therefore there is no communication-control co-design. In this paper, we aim at minimizing the wireless resources consumption of a WNCS making use of PPC, as in [6], but considering the application of incremental redundancy HARQ. Therefore, instead of using all the available channel uses for transmitting a packet with the control commands, we consider the transmission of an initial shorter packet conveying the control commands, therefore with increased error probability, but that saves a considerable amount of wireless resources.…”

“…In case of failure, additional redundancy is sent in a second transmission, as to guarantee the required reliability within the latency budget. Thus, this paper addresses the matter of obtaining the optimal prediction length of the controller, utilizing short blocklength packets along with HARQ, as to achieve even lower wireless resources consumption than in [6], [10]. Numerical results show that we can save as much as 45% of the resources in some scenarios when compared to [6], [10].…”

Optimizing Resource Allocation in URLLC for Real-Time Wireless Control Systems

“…We notice that there are some research on communicationcontrol co-design [23]- [27]. For instance, in [24], the authors obtained the optimal control sampling period and communication time delay and reliability by simulation analysis based on the existing communication protocols.…”