The subway density of mobile phone users is so great that almost all passengers will play mobile phones. The solution forms a high-power wifi jammer at each subway station, which may block all program control instructions, which is a great risk and threat to the operation of the subway. But I don't think it is possible to obtain a radio communication service license because it will reduce profits. In fact, the Shenzhen Metro was still rejected by the broadcast. They used a good measure --- the best WiFi signal blocker.
In early 2012, the Shenzhen Metro Group discovered the problem and applied it to the Shenzhen Municipal Traffic Management Bureau. 3G and WiFi signals on all Shenzhen subway lines were blocked. As the system was attacked by unknown sources, many lines were emergency braked underground. We must activate the automatic protection function and we cannot drive the operation too quickly. The incident caused public concern over the safety of subway operations.
After research, they found the real reason. Metro Portable Signal Jammers that can use the same information for passengers will interfere with each other. We know that most smartphones are equipped with WiFi devices. Although the CASCO signal system is the most advanced CBTC company, the safest and most efficient is that it is difficult to say that you know the speed of this highly developed technology, but the CBTC system may bring new problems to new wireless transmission equipment.