Experts call for the planning of the subway special frequency WiFi

Absrtact: Experts call for the planning of the subway special frequencies WiFi Shenzhen Subway signaling system uses the common frequency band, by the citizen's portable WiFi force to stop. At present, many of the domestic subway lines of the signalling system, also uses the common frequency band. This was referred to by netizens, the subway builders lack

Experts call for the planning of the subway special frequency WiFi

The Shenzhen Subway signaling system uses the common frequency band, by the citizen's portable WiFi force to stop. At present, many of the domestic subway lines of the signalling system, also uses the common frequency band. This was referred to by netizens, the subway builders lack of foresight. Free WiFi coverage in the city is a growing trend. How to solve this contradiction, Shenzhen Metro said, hope that the national level to pay attention to the planning of the special frequency of the subway.

Shenzhen, director of the Rail Traffic Construction office, said yesterday to reporters in South Qiang that for months, the subway group had reflected to them several times that the train was being disrupted by signals during its operation. Qiang said: "The subway to our report and South are reported basically the same content, do not exclude other interference factors, but the main suspect is the portable WiFi router signal interference." ”

As for the progress of the accident resolution, Qiang replied: "The recent subway Snake Mouth line and the central midline fault, the subway technical department is also doing tests to find the cause and rectification." Now the progress of the snake mouth Line fault has been basically eliminated, is debugging the ring centerline. ”

Qiang also said, "the government is very concerned about this matter, but did not form an investigation team." The Metro Group has set up its own expert research team to investigate the series of incidents. We will urge them to have an answer to the public as soon as possible. ”

Shenzhen subway, the reason that WiFi forced to stop Shenzhen Subway, and Shenzhen subway construction in the forefront of the country also has a certain relationship. According to the subway engineer, the communications operator built the base station on the platform of the Shenzhen subway, and the subway tunnel has already covered 3G signals. Guangzhou subway has not yet covered 3G network, for the already opened since the establishment of the WiFi network, but also more cautious, repeated testing. In his view, it is precisely because of the 3G network, passengers can easily through the portable WiFi to the 3G signal into the WiFi signal, thereby affecting the subway itself signal communication. "There is no such problem without covering the 3G network. "He thought. A person familiar with the Shenzhen Metro said that in the long run, it is hoped that the country will approve the special frequency band of the subway.

Question 1

Subway to save money by using a common band?

"We scoff at the use of the French are paid special frequency band, the Shenzhen Subway in the major public safety related to the project to save the two money, it is nothing to say." "Well-known science squirrel will members, communications professional teacher @" said, "Shenzhen subway Shekou line, such as three lines are not approved and paid for the 2.4Ghz public band, does not consider external interference, only the Longhua line is paid 5.8Ghz band."

In addition to the signaling system, trains also involve passenger information systems, such as trains on television. The Longhua line uses the 5.8Gzh band in passenger information systems. This is a toll band. Because the user is not many, this frequency band is relatively stable, the possibility of being disturbed is small.

Longhua Line is operated by the MTR Corporation. Shenzhen Subway also told South reporters, Longhua line at that time chose 5.8Ghz, but also take into account the problem of interference. Because the Longhua line has a large number of sections on the road, the electromagnetic interference is more than the underground tunnels, they worry that 2.4Ghz will be unstable.

Shenzhen Metro: Choice of public frequency and bidding

In response to the user's query to save money, said a person familiar with the Shenzhen Metro said, in fact, the application of the 5.8GHZ payment does not need much money. Shenzhen Radio Authority also confirmed that the band is a kind of national resources, the MTR if the use of pay bands, the annual cost is not million yuan. Shenzhen Metro The people said that the Shenzhen metro line to choose the 2.4Ghz mode of communication, in fact, with the tender relationship. Since the 2.4Ghz is a consistently used frequency band, the signal contractor has done similar works before, so it is logical that this communication method has also been introduced to the Shenzhen subway.

In fact, Shenzhen Radio office, deputy director of the Yangspring in the interview with reporters in South, also said that the Shenzhen subway does not use the public band, because of the risk of interference. Why does the Shenzhen MTR still insist on using this equipment despite warnings?

Shenzhen Orbital office concerned person Qiang stressed that, "some big cities such as Beijing, Shanghai, Guangzhou, etc., as long as the use of the CBTC system, signal transmission channels are in 2.4GHz." "However, the user @ an AO-Sam Razor thinks that the design of the subway signal system using the open band is a lack of forward-looking errors."

A person familiar with the Shenzhen Metro said the technology is developing too fast, even in the 5.8Ghz band, and it is likely to develop quickly into a public band. In the long run, I hope the country can approve the special frequency band.

Question 2

Can a self-built WiFi force stop the subway?

In fact, WiFi interferes with the subway signaling system, which has occurred in Shanghai before, because it was in the testing phase and the relevant issues were not seen in the media, according to an engineer from the Shenzhen Metro.

According to the Shanghai Oriental Morning Post, the Shanghai Metro line Line 6 to line Line 11 have adopted the CBTC signaling system. After the Shenzhen subway was hit by WiFi, the Shanghai Subway said in an interview with the Oriental Morning Post that "the Shanghai Subway has never had such an incident since its operation." But according to the Shenzhen subway engineer, they learned from other companies that the Shanghai subway was not forced to stop by a portable wifi, but that it had been installed with WiFi interference. According to him, the Shanghai subway once wanted to cover free wifi in the subway, but after 6 tests, it was found to have an effect on the subway's own signaling system, so so far the Shanghai subway has not opened free WiFi.

The wireless City program in Shanghai is also being advanced, with WiFi network already covered on the bus. But in the face of this, in July this year, the Shanghai Metro said to the public that it would not consider covering WiFi for the time being. The reason for this is not to cover WiFi, insiders say. South all reporters yesterday called Shanghai subway operators, a person in charge said he is only responsible for operations, the signal is not clear, and said only signal company clear.

Shenzhen Metro: How to safely cover wireless network remains to be studied

Shenzhen Rail Traffic Construction Office Director Qiang yesterday told South all reporters: "Currently in the Shenzhen Subway can not fully promote the construction of the WiFi, because in the process of the introduction of the discovery of WiFi signals will interfere with the subway signaling system." How to safely cover the wireless network is also a topic we are studying. ”

Question 3

Casco Signaling system defective?

At present, Shenzhen operates three lines, Shekou line, ring midline and Longgang line are all using the CBTC system, but the signal systems contractor inconsistent. The line between the Shekou and the ring is casco. The Longgang line, formerly operated by an independent company, is now incorporated into the Shenzhen Metro Group, using a signaling contractor, Bombardier. In fact, most of the road in the Longgang line is on the ground, theoretically, more interference, but the line was tested yesterday, found not to be affected by the portable WiFi.

This has also allowed many people to target the signal contractors, is there a certain flaw in the signaling system itself? Longgang Line in the interview told South reporters, use 2.4Ghz band communication, is to use to frequency point. If the passenger's portable WiFi is at the same frequency as the Metro's signalling system, it may interfere with each other. So Bombardier uses spread spectrum technology to transform conventional frequency points. The frequency of the passengers ' portable WiFi is routine, so it is generally not affected by the frequency-point anastomosis of the subway signaling system. The official also stressed that the Bombardier signaling system is stronger.

Shenzhen Metro: There may be insufficient signal strength

An engineer in Shenzhen Metro said that the Casco signaling system used by the Shekou line and the central centerline did not use spread spectrum technology, and there might be problems with insufficient signal strength. However, at present, after transformation, the ability of the snake-mouth line anti-interference has been significantly improved, the effect is good. The centerline of the ring will also begin to make related improvements immediately.