Coverage Analysis of Cooperative Relaying for Urban Transportation Systems in Tunnels

Communication availability is critical for the seamless and automated operation in urban transportation systems. Existing signaling systems for railways allow the trains to communicate only with the infrastructure, hence limiting the communication availability during handovers, failures, and unexpected operating conditions. We theoretically study the communication coverage improvements to be achieved by allowing the trains to relay signaling data to and from their neighboring trains under outage. We formulate a flexible spatial model to represent train locations statistically. Our model can be applied to different railway and traffic conditions by adjusting the distance-dependent probability function. We use the two-slope path loss model which has been shown to display good fit to signal measurements in tunnels. Our findings show that enabling cooperative relaying can reduce the outage events by up to 90% in dense railway networks.