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Shanghai Metro counts on RFID RTLS

Use Cases | By B-Id | 21 October 2013
The Shanghai Metro's rail network is to be expanded to around 970 kilometers and 22 train lines by 2020. The Shanghai Metro's rail network is to be expanded to around 970 kilometers and 22 train lines by 2020. Photo: Kentaro IEMOTO@Tokyo / flickr.com

Subway localization

In cooperation with Partners B-Id developed a real time localization solution for more than 400 trains

Shanghai Metro was put into operation only in 1993, however it is one of the most fast growing subway systems worldwide. Every day more than 400 trains are on their way on around 439 track kilometres. Around seven million passengers averagely rely on the subway as means of transport every day. An extensive control and signal system is already installed. Yet Metro saw optimization potential regarding the gain of real time data to improve the efficiency during operation. Within three years B-Id developed an RTLS solution, comprising active 2.45 GHz technology and passive LF frequency, in cooperation with the Chinese company Shanghai Super Electronics Technology. „RFID im Blick“ spoke to B-Id managing director Yiwen Jin about the application.

„The challenge of the Shanghai Metro was to design and implement a system which allows to create a logbook with real time data. Information about which train arrives at which station or departs this station helps to improve the operation procedure management and as a consewuence for instance to react faster on unforseen situations“, Yiwen Jin reports.

The subway: A challenging environment

Especially two challenges necessarily require a long period of development as well as comprehensive tests. First, there are numerous sources of electromagnetic interference at the stations, which are partly operated in the same frequency ranges like the LF frequency and 2.45 GHz, such as active Wifi or Bluetooth radio interfaces of the passengers' smartphones for instance. Secondly the distances between the trains and the platforms are very small, which might lead to the detection of the wrong transponders. „As the sources of interference differ from station to station, we specifically adjust the readers as well as the LF and active transponders in comprehensive tests. In the LF range, readers vary between 114 kHz and 116 kHz, in the GHz range, readers automatically set the frequency between 2.4000 GHz and 2.4853 GHz“, Yiwen Jin explains.

LF and active 2,45 GHz RFID combined in RTLS

The used LF chips with an adjustable spherical detection zone with a diameter of four to eight meters, which were integrated into active transponders already, mounted in the trains, use the energy provided by the readers at the stations to activate the 2.45 GHz transponders and at the same time forward the train's position data which the active transponders forward to the readers at the stations. „Using this combination, we guarantee an optimal detection rate. As the trains have a speed of up to 80 kilometers per hour, the detection would be impossible using solely 2.45 GHz technology. At these speeds only LF technology works reliably“, says Jin and adds: „Without using LF technology as a trigger, this application had been impossible to implement. For more than half a year, the solution has been running stably. As the batteries provide the active transponders with energy for at least three years, we guarantee that all trains are reliably recorded on their rides in real time.“ In total LF technology, which is crucial for the RTLS system to function, was installed and configured in more than 1 000 readers and 800 tags of Shanghai Metro's rail network.

Solution transferability

The system which was specifically developed for Metro Shanghai can be used in a number of further applications, with regard to its function, for instance at the automatic vehicle detection in parking garages or for an extended access control, as Yiwen Jin reports: „An RTLS does not only allow to detect, who operated which room at which time, but also where exactly they were located within the room. In cooperation with a company which installs camera based monitoring solutions, we developed a solution for a customer's server room to create personalized film sequences using RFID RTLS and cameras to point out exactly, which employee operated the server at which time. Furthermore access rights can be controlled. Depending on the environment, the readers can also communicate actively with the respective transponders in UHF bands 433 Mhz, 868 Mhz, 915 Mhz, as well as Wifi.

The article was published in the September issue 2013 of the magazine „RFID im Blick“.

Last modified on Wednesday, 21 October 2015 17:46
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