Shenzhen official test said portable WIFI signal does not affect subway operation

From 8:15 to 9:30 on the 1st of this month, many trains on the Shenzhen Metro Shekou Line were suspended. The time for each suspension was one to two minutes, causing a large number of passengers to be transferred several times and stranded at the station along the line. On the 4th, some media reported that the cause of the train failure was due to the portable WIFI hand held by the passengers. One stone provoked thousands of layers of waves. The WIFI forced the stop of the subway for a moment and caused public debate.

After the accident, the Shenzhen Radio Management Committee organized Shenzhen subways and operators and other related departments to test the signals in the Shekou line twice. The results showed that the relevant portable WIFI signals in the subway did not affect the subway operation system.

However, there are also insiders who analyze that the uncontrollable frequency band of portable wireless WIFI routers that a telecommunications operator newly introduced to the market is the main cause of signal interference to subway operation.

Netizens said that if WIFI can force stop the subway, then the future mobile phone to prepare for "metro mode" Caixing.

According to informed sources, Shenzhen Metro will launch autonomous and controllable WIFI Internet access on some lines by the end of the year.

Metro Group Denies WIFI Forces Subway to Stop

Says experts are investigating Shekou line signal failure yet results

On the early morning peak of November 1, many trains on the Shenzhen Metro Shekou line failed to exit the service due to multiple failures. Some of the trains were suspended. The time for each suspension was one to two minutes, resulting in a large number of passengers being forced to transfer several times and staying. In the station along the line.

On the same day, the Shenzhen Metro official stated that the Shenzhen Metro Shekou multi-subway train had stopped due to undisclosed reasons. The Shenzhen Metro issued a message on the official Weibo. In response, it stated that the Shekou Line's multiple trains generated emergency braking due to the automatic protection function of the signal system. The initial judgment was that the signal system was disturbed by unknown reasons from outside, resulting in automatic security protection of the system. On November 4, media reports said that the reason for the multiple stoppages of the Shekou line has been initially locked in the portable WIFI hand held by the passengers, citing people familiar with the matter. The signals sent by the portable WIFI conflict with the signals used by the subway itself to transmit information. Their frequency bands are the same. Metro and wireless operators suspect that the interference source is not an ordinary wireless routing signal, but rather a WIFI signal that passengers use their mobile phones as hot spots.

According to the WIFI forced stop of the subway, the person in charge of the Shenzhen Metro Group told the reporter of the Yangcheng Evening News that the cause of the accident was still under investigation and the media coverage of the WIFI forcing the stop of the subway was not recognized. In order to find out the specific reasons, the Metro Group has organized experts to investigate the signal failure of the Shekou line and the results of the survey have not yet come out.

Operators recommend that subways open a proprietary frequency band

It may be caused by the subway signal system and civil WIFI sharing band causing failure

After the accident, the Shenzhen Radio Management Committee organized Shenzhen subways and operators and other related departments to test the signals in the Shekou line twice. The results showed that the relevant portable WIFI signals in the subway did not affect the subway operation system.

Some experts stated that there are defects in the subway signal system. According to industry sources, the National Radio Authority’s WIFI, which is open for civilian use, is within the 2.4G band and is far away from trunking communications, and the interference is less likely. Some passengers' cameras and mobile phone DVs have their own WIFI devices. If a WIFI interferes with the train, then the subway communication system becomes the legendary bean curd system.

Some operators believe that, through technical analysis, many can only say that the subway signal system shares the band with civilian WIFI, occupying the civil WIFI channel. The operator analyzed that the frequency used by the subway train signal system is also civil WIFI in the 2.4G band, and it is not impossible to generate interference between them. However, the 2.4G band WIFI is a frequency band that the State Radio Administration Bureau opens for civil WIFI. Occupation of civilian frequency bands. Now that the Ministry of Railways has applied for its own proprietary frequency band, all railway trains cannot interfere with civil WIFI. It has been proposed to close the operator's 3D coverage within the subway, which is completely unscientific, and all WIFI subways should have their own proprietary WIFI band.

Regarding the operator’s claim, the Shenzhen Metro Group responded that not only did this problem exist in the Shenzhen Metro, but the subway signal applied for a proprietary frequency band. This is an industry issue and it is currently not definitive.

Net friends

Netizens Tune: Mobile Phones Must Have "Metro Mode"

The netizen frost played eggplant: The country's spectrum resources are divided, and WIFI2.4G will interfere with the signal system of the subway. This law is a reason for nonsense.

Shan Zenghui: If the subway is so fragile, even hand-held WIFI can lead to failure, it is simply a super bad design.

Wild Wolf: If the subway signal is so fragile, the next time you take the subway, you will have trouble shutting everyone down so you don't have to stop. The subway must be made like an airplane. The mobile phone must be tuned into the "metro mode."

Road to return home: If the WIFI used by the general public can stop and fall, it shows that there is a security gap in the subway signal system.

an expert

Doubt

New push WIFI router band is not controllable

Can interfere with subway running signals

Suggest Shenzhen Metro to build a controllable wireless system

An industry source, who asked not to be named, told reporters that the uncontrollable frequency band of portable wireless WIFI routers launched by a certain telecommunications operator in Shenzhen was the main cause of signal interference to the subway.

According to industry insiders, Shenzhen’s operators are currently selling a portable wireless WIFI router whose main function is to convert the 3G signals it has laid in Shenzhen into wireless WIFI signals. The use of the equipment on the ground has not been found yet. The report of the impact of the system, but due to the characteristics of its random capture frequency band directly interferes with the CTBC signal of the subway operation, it may cause the subway signal protection device to start automatically. The direct consequence is that the subway train will be out of service.

"Compatibility and frequency locking are the key to solving problems. Compatibility is the premise of frequency locking. Frequency locking is the purpose of compatibility. For example, the subway CBTC system already occupies part of the channels. The future wireless WIFI system can only be used and must be locked in. Other channels, only in this way will not form a mutual interference between signals, to completely solve the interference problem.” The personage inside the industry said that while the portable wireless WIFI provided by Shenzhen operators is based on the idea of ​​underground ground interoperability, the frequency band is random and not Controlled. It is therefore feasible and necessary that the MTR must establish an independent, compatible and frequency-locked wireless WIFI system that belongs to the subway.

sound

E era era of subway Internet access should be sparse should not be blocked

According to industry insiders, the urgent need of 4 million subway passengers and 30 minutes of ride time per day is a realistic and urgent need for passengers to access the Internet in the era of mobile Internet. The environment within the subway is completely different from that of the ground, so it is also bound to face technical difficulties and complexity of implementation. However, in the face of the urgent needs of the public, we must not take food out of the situation. Instead, we should take advantage of the situation. Under the premise of ensuring security, we must quickly form a set of effective solutions, and the needs of the public should be sparse.

Shenzhen Metro will build autonomous controllable WIFI system

Subway operation is a major livelihood project that concerns the vital interests of the people and is a major project with high technology and high investment. Therefore, the subway is no small matter.

Faced with the needs of the public, according to informed sources, the Shenzhen Metro will soon launch an autonomous, channel-controllable wireless WIFI system to address the urgent needs of the public for WIFI Internet access. It is expected that some lines will be launched by the end of the year and Shenzhen is expected to be the first city to achieve Internet access within the metro.

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