Wireless channels, also known as fading channels, are inherently randomly time-varying, due to the small-scale effect of multipath, and larger-scale effects such as path loss and shadowing by obstacles. This can cause the transmitted signals to be attenuated, distorted, delayed, or lost in unpredictable ways. Signals transmitted by different sensors/devices over the wireless medium can also interfere with each other. Maintaining acceptable quality of service in such conditions is a challenging problem.
In networked control systems research, often the wireless environment has been abstracted into models such as i.i.d. (or Markovian) packet dropping links, or has regarded fading as multiplicative noise, which can lead to conservative designs. Our view is that techniques and ideas from wireless communications itself can also be effectively utilized in the study of networked control systems, leading to improved performance.
Power control is a key enabling technology for wireless communications, serving to compensate for the time-varying channel gains and to provide quality of service guarantees to users. Energy harvesting, where the sensor can extract energy from the surrounding environment such as via solar, thermal, mechanical vibrations or electromagnetic radiation, can dramatically increase the lifetime of nodes in wireless sensor networks. Coding schemes can improve the reliability of the transmitted information, with network coding even able to increase throughput. Multi-hop networks and cooperative communications via the use of relays have been identified as some of the key enabling technologies for fifth generation (5G) mobile networks. These are some of the techniques which we have introduced in our work.&nb
Selected Publications on Wireless Estimation
A. S. Leong, D. E. Quevedo, A. Ahlen and K. H. Johansson, "On Network Topology Reconfiguration for Remote State Estimation'', IEEE Transactions on Automatic Control, to appear
J. Wu, Y. Li, D. E. Quevedo, V. Lau and L. Shi, "Data-Driven Power Control for State Estimation: A Bayesian Inference Approach", Automatica, vol. 54, no.4, pp. 332-339, Apr. 2015
M. Nourian, A. S. Leong, S. Dey and D. E. Quevedo, "An Optimal Transmission Strategy for Kalman Filtering over Packet Dropping Links with Imperfect Acknowledgements'', IEEE Transactions on Control of Network Systems, vol. 1, no. 3, pp. 259-271, Sep. 2014
D. E. Quevedo, J. Ostergaard and A. Ahlen, "Power Control and Coding Formulation for State Estimation with Wireless Sensors", IEEE Transactions on Control Systems Technology, vol. 22, no. 2, pp. 413-427, Mar. 2014
D. E. Quevedo, A. Ahlen and K. H. Johansson, "State Estimation over Sensor Networks with Correlated Wireless Fading Channels", IEEE Transactions on Automatic Control, vol. 58, no. 3, pp. 581-593, Mar. 2013
D. E. Quevedo, A. Ahlen, A. S. Leong and S. Dey, "On Kalman Filtering over Fading Wireless Channels with Controlled Transmission Powers", Automatica, vol. 48, no. 7, pp. 1306-1316, Jul. 2012
Selected Publications on Wireless Control
E. Peters, D. E. Quevedo and M. Fu, "Controller and Scheduler Co-design for Feedback Control over IEEE 802.15.4", IEEE Transactions on Control Systems Technology, to appear
B. Demirel, Z. Zou, P. Soldati and M. Johansson, “Modular Design of Jointly Optimal Controllers and Forwarding Policies for Wireless Control”, IEEE Transactions on Automatic Control, vol. 59, no. 12, pp. 3252-3265, Dec. 2014
D. E. Quevedo and I. Jurado, "Stability of Sequence-Based Control with Random Delays and Dropouts", IEEE Transactions on Automatic Control, vol. 59, no. 5, pp. 1296-1302, May 2014
D. E. Quevedo and D. Nesic, "Robust Stability of Packetized Predictive Control of Nonlinear Systems with Disturbances and Markovian Packet Losses", Automatica, vol. 48, no. 8, pp. 1803-1811, Aug. 2012
D. E. Quevedo, J. Ostergaard and D. Nesic, "Packetized Predictive Control of Stochastic Systems over Bit-Rate Limited Channels with Packet Loss", IEEE Transactions on Automatic Control, vol. 56, no. 12, pp. 2854-2868, Dec. 2011