the suica system

during my first japan trip, i was struck by how convenient the digital suica card was - it works with your phone off too, and allegedly when your phone is dead. so i wanted to learn how it works.

found a nice report https://www.ejrcf.or.jp/jrtr/jrtr50/pdf/6_15_web.pdf from 2008 on dev of IC cards themselves

• expandable and reliable system for automatic fare collection

• IC card ticket system was introduced 2001 and uses autonomous decentralized architecture

• GOAL: stable, reliable, high-speed processing is a necessity - railway services continue everyday w/o break

  • in morning/evening rush, about 24 million transactions occur at ticket gates daily
  • reliability is necessary due to dealing with money
  • contactless was a goal because of how quickly passengers pass through the gates

• introducing the IC cards required coexistence with original magnetic system

• contactless IC card gates use a signal field to detect the card, and authenticate it

  • read, evaluate, write, reconfirm
  • 0.2s processing time

• read/write processing time must be less than 0.1s so passengers do not need to pause while passing through the gate

• three makers of contactless IC cards

  • 2 used medium-freq radio waves
    • required an emitter circuit to generate data transfer signal
  • 1 used quasi-microwaves
  • all required built-in batteries

• tried battery-equipped IC cards w quasi-microwaves

• after field testing - Suica became battery-free, with power provided via electromagnetic induction

• the usage of an IC card is very variable/unstable - people wave the cards at the gate differently

• solution: autonomous decentralized architecture, and changing wave motion to “touch and go”

  • gates auto process cards and store data w/o accessing center server
  • center server performs data matching with Autonomous Data Consistency to secure high reliability?

• to assure minimum operation when equipment fails

  • data is processed by wireless communications at gates
  • async online real-time processing
  • gates, ticket machines, station servers are connected by local area network (LAN)
  • station servers and center server are connected by wide area network (WAN)

• how to merge the diff information systems and network protocols? → Heterogeneous Autonomous Decentralized IC card ticket system

• system diagram on page 6

• every suica card has unique ID

• if station server fails, data will not be transferred with center server - but gates can store data so basic operations continue

  • most recent 20 data processing stored on the card ; 3-days worth stored in the gate
    • 3 days is max time w/o fixed communication line
  • whenever communication is possible, gate data is uploaded to station server
  • when possible, station data is uploaded to center, which stores up to 6 months

• mobile Suica introduced in 2006