Random Access Design for Wireless Control Systems

TL;DR

This paper develops a distributed, threshold-based channel access policy for wireless control systems that minimizes power consumption while maintaining control performance amid interference and fading.

Contribution

It formulates an optimization problem for channel access, proves the optimal policies are decoupled and threshold-based, and provides a distributed iterative solution without requiring sensor coordination.

Findings

Optimal policies are decoupled and threshold-based.

Sensors transmit only under favorable fading conditions.

Distributed iterative algorithm computes policies without coordination.

Abstract

Interferences arising between wireless sensor-actuator systems communicating over shared wireless channels adversely affect closed loop control performance. To mitigate this problem we design appropriate channel access policies for wireless control systems subject to channel fading. The design is posed as an optimization problem where the total transmit power of the sensors is minimized while desired control performance is guaranteed for each involved control loop. Control performance is abstracted as a desired expected decrease rate of a given Lyapunov function for each loop. We prove that the optimal channel access policies are decoupled and, intuitively, each sensor balances the gains from transmitting to its actuator with the negative interference effect on all other control loops. Moreover the optimal policies are of a threshold nature, that is, a sensor transmits only under favorable local fading conditions. Finally, we show that the optimal policies can be computed by a distributed iterative procedure which does not require coordination between the sensors.