Communication-Based Train Control (CBTC) Systems With Cooperative Relaying: Design and Performance Analysis

A communication-based train control (CBTC) system is an automated train control system using bidirectional train-ground communications to ensure the safe operation of rail vehicles. CBTC systems have stringent requirements for communication availability and latency. Most existing CBTC train-ground communication systems work in the infrastructure mode without train-train communications. Due to unreliable wireless communications and frequent handoffs, existing CBTC systems can severely affect train control performance, train operation efficiency, and the utility of the railway. In this paper, we use recent advances in cooperative relaying to enable train-train communications and, consequently, enhance the train control performance of CBTC systems. Trains act not only as end communication points but as relays for other trains as well. Unlike existing works on cooperative relaying, in this paper, linear quadratic cost for the train control performance in CBTC systems is considered as the performance measure. We jointly consider cooperative relaying and handoff decision issues in CBTC systems. Moreover, to mitigate the impacts of handoff latency on the train control performance, we propose an optimal guidance trajectory calculation scheme in the train control procedure that takes full consideration of the tracking error caused by handoff latency. Simulation results show that the train control performance can be substantially improved in our proposed CBTC system with cooperative relaying.