Reliable wireless connections for fast-moving rail users based on a chained fog structure

Currently, 3G and 4G networks provide customers with high-speed wireless services almost everywhere. However, the wireless connection is often unstable and unreliable, especially for fast-moving end users (e.g., those on trains and buses). To investigate the severity of this problem, we conducted real experiments on fast-moving trains to investigate the quality of 3G connections. From the results, we found that 1) from the temporal perspective, the 3G connections were not stable and suffered from frequent disruptions of connectivity, and 2) from the spatial perspective, the connections that were established in different train compartments were largely independent. These two findings motivate us to propose a brand-new fog computing structure, which acts as an intermediate layer between the end users and the 3G infrastructure. This new fog structure introduces a series of mutually chained network gateways that are located in different compartments. This structure addresses the aforementioned problem of unstable connectivity and thus ensures reliable wireless service for fast-moving users, such as passengers on trains. We performed a series of theoretical and empirical analyses to evaluate the performance of the newly proposed structure. All of the experimental results suggest that our proposed fog structure greatly improves the reliability of wireless connections on fast-moving trains.