Multi-layered Data Consistency Technology in Autonomous Decentralized IC Card Ticket System

High-load transaction systems such as the IC (integrated circuit) card ticket system require high performance, high reliability, and service continuity. However, the wireless communications have a problem that higher performance at the gates results in lower reliability in the data. The solution is the Autonomous Decentralized Architecture, in which "IC cards," "terminals, " and a "center server" are designed as the autonomous nodes. Based on the architecture, two technologies have been introduced: "autonomous decentralized fare calculation algorithm" for high performance and "autonomous decentralized data consistency technology" for high reliability. This paper looks into the multi-layered data consistency technology which assures service continuity, using heterogeneous data fields with various time ranges. Appropriate values are considered through theorization, modeling, and simulation. These conditions are used in the practical "Suica" system at East Japan Railway Company and the system is running satisfactory, without any fatal errors.