Coverage Expansion through Dynamic Relay Vehicle Deployment in mmWave V2I Communications

In millimeter wave (mmWave) vehicle-toinfrastructure (V2I) communications for autonomous vehicles, the small coverage of road side units (RSUs) is an open problem. We propose a multi-hop relaying method using dynamic vehicle deployment in order to increase the coverage of RSUs. The key idea of our method is to leverage the movement controllability of autonomous vehicles to extend the multi- hop relay distance. The proposed deployment method considers blockage because it is a crucial problem in mmWave communications, although it is not a crucial problem in microwave communications. We formulate the deployment problem as an optimization problem and obtain its lower and upper bounds performances. We also introduce a mmWave connectivity graph, from which the vehicle position that achieves the lower bound performance can be obtained by solving a shortest-path problem. Simulation results demonstrate that even when only 7.5% of all vehicles'' positions are controllable, the proposed deployment method can achieve a coverage of 80%, which is more than twice the coverage achieved by the relaying without deployment.