Design and Optimization of Cooperative MAC Protocol for Mobile Ad Hoc Network-Enabled Train-to-Train Communications

As urbanization progresses, train-to-train (T2T) communication for communication-based train control (CBTC) systems has become crucial, leading to mobile ad hoc networks (MANETs) between trains. The dynamic network topology poses challenges to the high reliability needed for safe rail transportation information. To address this, we propose a cooperative medium access control (MAC) communication scheme based on distributed time division multiple access (DTDMA) for T2T communications. This scheme uses multiple nodes in their idle time slots to cooperatively forward failed data. To ensure the reliability and effectiveness of this cooperation, we propose a cooperative MAC protocol and frame structures combined with the automatic repeat request (ARQ) mechanism for reliability and effectiveness. Additionally, we propose a cooperative node selection method, modeled as a Markov decision process (MDP), to maximize system throughput and minimize overhead. For actions with hybrid space, we use the soft actor-critic (SAC) to set a continuous threshold and select nodes discretely. Simulations show that our proposed cooperative MAC protocol and cooperative node selection method effectively enhance transmission reliability.