Can I have wifi on the subway?

Netizen Johnson: Chuan Beijing subway Many lines opened WiFi, this thing is true? Can I open wifi on the subway? Tencent Technology: Beijing Subway opened WiFi news has been proved to be a rumor, the Beijing Subway company said it did not know about it, the MTR also clearly responded that no such thing. There have been a number of events in Shenzhen that have been suspended from the subway, and the reasons for the incident were analyzed by the subway operator, which led to the collision between the frequency of the subway signal and the frequency of the launch of the portable WiFi router. There is still some controversy about whether WiFi can be installed on the subway. The basic situation is as follows: first, mobile WiFi interferes with the subway communication it is possible that wireless communication needs to be transmitted in the air, as is the case with WiFi and Metro radio dispatching. If two signals use the same frequency, there may be interference. In China, WiFi is used in the 2.4GHz public band, unfortunately, many of the domestic subway using the CBTC (wireless communication based automatic train control) system, but also with this band for communication. But the 2.4GHz band has many different protocols, like an eight-lane road, Wi-Fi and Metro communications that may or may not go together. But the subway belongs to the relatively high speed transportation, its dispatch safety is the most should safeguard. Therefore, in the event of possible signal interference, it is understandable that WiFi is shut out of the subway. Second, to signal the installation of guardrail line? There is a little understanding of wireless communications netizens asked, if the fear of interference, we give WiFi and subway scheduling different channels, can not be perfect to solve it? Indeed, at the same frequency, wireless communication can circumvent interference by setting different channels. But the barrier between the channels is not very strong, in order to completely avoid interference, the channel interval is generally set to more than 4MHz. But even so, we still can't guarantee that Metro communications and mobile WiFi can be peaceful. Wireless headset, Bluetooth equipment, and some personal terminal WiFi hotspots, are likely to form hurdles, jump to the subway communication channel. Three, there is no solution to it? In fact, the root of the problem is that the 2.4GHz band of WiFi is a public network, which is already available to the public, and if Metro communications can choose other frequencies, the problem will be solved. November 2006, the Shanghai Radio Administration has prepared a study on the analysis of electromagnetic compatibility in the 2.4GHz frequency band The application analysis of the wireless CBTC system in rail transit shows that 2.4GHz is a common frequency band and can not completely avoid the possibility of CBTC being disturbed, The Shenzhen Radio Authority has repeatedly questioned the safety of this band on the subway. Relevant experts also said that the subway control system should not use communication technology similar to the public communication, but should use dedicated communication frequency, must be separated from the public communication frequency. In this regard, rail transport is doing better. For some areas in the vicinity of the train line to deploy WiFi coverage, due to railway communications such as GSM-R system, the use of frequencyFor 800-900mhz, it belongs to the special communication frequency rather than the public band, so it will not be disturbed by WiFi. If you get a WiFi hotspot by train, there's no need to be afraid, maybe it's a compensation for our inability to experience WiFi in the subway ...