Denial-of-service attacks on cyber–physical systems with two-hop networks under round-robin protocol

We formulate and analyze optimal denial-of-service (DoS) attacks for remote estimation arising in cyber–physical systems with a two-hop network. The measurements of sensors are transmitted to the remote estimator over a relay, which can be congested by a malicious attacker. Similar to the estimator, the relay has sufficient computational capability to buffer the received information and estimate the physical state. In addition, to prevent data collisions, only one of the sensors can access the communication channel at each time step under the round-robin protocol. We propose an optimal attack schedule by restricting our attention to dealing with the scenario, where the attacker with energy constraints can launch interference to the two wireless communication channels at the same time during the attack period. Finally, the theoretical results are demonstrated by numerical examples.