  This paper presents a distributed multi-layer ring barrier coverage
algorithm. In order to achieve single-layer ring barrier coverage, a
distributed single-layer ring barrier coverage algorithm that maximises the
probability of monitoring is proposed. Considering the security risks of
single-layer barrier coverage, a distributed adjustment mechanism between
multiple layers of barriers is designed and combined with the single-layer ring
barrier coverage algorithm to propose a distributed multi-layer ring barrier
coverage algorithm. Furthermore, we present a theoretical analysis of the
proposed algorithm to demonstrate its effectiveness and necessity. Finally, our
algorithm is verified by numerical simulation and experiment.
