Parallel Offloading and Resource Optimization for Multi-Hop Ad Hoc Network-Enabled CBTC With Mobile Edge Computing

The emergence of communication-based train control (CBTC) system within urban rail transport has improved the efficiency of safe train operations. At the same time, the CBTC system enhances the reliability of the train system and lowers latency of the data transmission. Nevertheless, there are still certain critical issues that need to be considered in the CBTC: 1) limited coverage and high maintenance costs of wayside equipment; 2) multiple ground devices configuration and complex system architecture; and 3) insufficient computing capacity of the train leads to heavy latency and energy consumption. To cope with the above problems, in this article, the multi-hop ad hoc network coexisting with train-to-train communication and train-to-wayside communication is applied to simplify the networking architecture, together with the employment of mobile edge computing (MEC) servers to provide massive computing and communication resources for trains. Meantime, a new CBTC framework is developed for computing offloading and resource allocation via multi-hop ad hoc network and MEC. Offloading decisions, offloading ratio, computing and communication resource allocation are integrated to minimize latency and energy consumption. Furthermore, the proposed problem is a mixed-integer non-convex problem that is transformed into a solvable convex problem, and the consensus alternating direction method of multipliers-based (ADMM) algorithm is employed to solve the problem. The simulation results show that our proposed method has remarkable advantages over other schemes.