Authorities temporarily shut down 3G service on two subway lines in Shenzhen, China in an effort to determine the cause of unexpected train stops between stations. According to Shenzhen Metro, the temporary removal of wireless services was done in order to test a theory that interference from mobile wireless networks was the cause. Almost every subway in mainland China is equipped with a wireless train operating system that operates on the 2.4GHz frequency—the same frequency used by wireless electronic devices.
The transport company believes that interference from portable Wi-Fi routers, which allow consumers to create mobile wireless networks using a single 3G SIM card, triggered the trains’ emergency brakes. Shenzhen Metro spokesman Wang Yuzhu explains that “portable routers appeared on the [Chinese] market last year … more than 80 percent of them were sold and used in Shenzhen.”
Shenzhen Metro plans to look into acquiring a special frequency to prevent future interference.
