Gathering of robots in a ring with mobile faults

In this paper, we consider the problem of gathering mobile agents in a graph in the presence of mobile faults that can appear anywhere in the graph. Faults are modeled as a malicious mobile agent that attempts to block the path of the honest agents and prevents them from gathering. The problem has been previously studied by a subset of the authors for asynchronous agents in the ring and in the grid graphs. Here, we consider synchronous agents and we present new algorithms for the unoriented ring graphs that solve strictly more cases than the ones solvable with asynchronous agents. We also show that previously known solutions for asynchronous agents in the oriented ring can be improved when agents are synchronous. We finally provide a proof-of-concept implementation of the synchronous algorithms using real Lego Mindstorms EV3 robots.