I. Introduction
RAIL-GUIDED transport systems have attracted much attention since they can provide greater transport capacity, superior energy efficiency, lower carbon emission, and outstanding features of punctuality and safety when compared with other mass transit methods. In traditional rail systems, a track circuit is commonly used to coarsely determine the location of a train and to transmit unidirectional ground-train control information. The coarse train positioning and low unidirectional communication throughput lead to low line capacity of the track-based train control (TBTC) system. The typical minimum headway, which is the time interval between two neighboring trains, of TBTC is several minutes [1].